Search

In this study, the effects of supplemental or night interruptional blue light (S-BL or NI-BL) positioning on morphological growth, photoperiodic flowering, and expression of floral genes in Chrysanthemum morifolium were investigated. Blue light-emitting diodes (LEDs) at an intensity of 30 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) were used for 4 h either (1) to supplement the white LEDs at the end of the 10 h short-day (SD10 + S-BL4) and 13 h long-day conditions (LD13 + S-BL4), or (2) to provide night interruption in the SD10 (SD10 + NI-BL4) and LD13 (LD13 + NI-BL4). The S-BL4 or NI-BL4 was positioned to illuminate either the shoot tip, the youngest leaf (vigorously growing the third leaf from the shoot tip), or the old leaf (the third leaf from the stem base). In the text, they will be denoted as follows: SD10 + S-BL4-S, -Y, or -O; SD10 + NI-BL4-S, -Y, or -O; LD13 + S-BL4-S, -Y, or -O; LD13 + NI-BL4-S, -Y, or -O. Normally, the LD13 conditions enhanced more vegetative growth than the SD10 periods. The growth of leaves, stems, and branches strongly responded to the S-BL4 or NI-BL4 when it was targeted onto the shoot tip, followed by the youngest leaf. The SD10 + S-BL4 or +NI-BL4 on the old leaf obviously suppressed plant extension growth, resulting in the smallest plant height. Under LD13 conditions, the flowering-related traits were significantly affected when the S-BL4 or NI-BL4 was shed onto the youngest leaf. However, these differences do not exist in the SD10 environments. At the harvest stage, other than the non-flowered LD13 treatment, the LD13 + S-BL4 irradiating the youngest leaf induced the most flowers, followed by the shoot tip and old leaf. Moreover, LD13 + NI-BL4 resulted in the latest flowering, especially when applied to the shoot tip and old leaf. However, the SD10 + S-BL4 or + NI-BL4 irradiated the shoot tip, youngest leaf, or old leaf all significantly earlier and increased flowering compared to the SD10 treatment. Overall: (1) Generally, vegetative growth was more sensitive to photoperiod rather than lighting position, while, during the same photoperiod, the promotion of growth was stronger when the light position of S-BL4 or NI-BL4 was applied to the shoot tip or the youngest leaf. (2) The photoperiodic flowering of these short-day plants (SDPs) comprehensively responded to the photoperiod combined with blue light positioning. Peculiarly, when they were exposed to the LD13 flowering-inhibited environments, the S-BL4 or NI-BL4 shed onto the leaves, especially the youngest leaves, significantly affecting flowering.

To investigate the relationship between the lighting direction-induced morphophysiological traits and post-harvest storage of lettuce, the effects of different lighting directions (top, T; top + side, TS; top + bottom, TB; side + bottom, SB; and top + side + bottom, TSB; the light from different directions for a sum of light intensity of 600 μmol·m−2·s−1 photosynthetic photon flux density (PPFD)) on the growth morphology, root development, leaf thickness, stomatal density, chlorophyll concentration, photosynthesis, and chlorophyll fluorescence, as well as the content of nutrition such as carbohydrates and soluble proteins in lettuce were analyzed. Subsequently, the changes in water loss rate, membrane permeability (measured as relative conductivity and malondialdehyde (MDA) content), brittleness (assessed by both brittleness index and β-galactosidase (β-GAL) activity), and yellowing degree (evaluated based on chlorophyll content, and activities of chlorophyllase (CLH) and pheophytinase (PPH)) were investigated during the storage after harvest. The findings indicate that the TS treatment can effectively reduce shoot height, increase crown width, enhance leaves’ length, width, number, and thickness, and improve chlorophyll fluorescence characteristics, photosynthetic capacity, and nutrient content in lettuce before harvest. Specifically, lettuce’s leaf thickness and stomatal density showed a significant increase. Reasonable regulation of water loss in post-harvested lettuce is essential for delaying chlorophyll degradation. It was utilized to mitigate the increase in conductivity and hinder the accumulation of MDA in lettuce. The softening speed of leafy vegetables was delayed by effectively regulating the activity of the β-GAL. Chlorophyll degradation was alleviated by affecting CLH and PPH activities. This provides a theoretical basis for investigating the relationship between creating a favorable light environment and enhancing the post-harvest preservation of leafy vegetables, thus prolonging their post-harvest storage period through optimization of their morphophysiological phenotypes.

Salinity is one of the primary abiotic stresses that seriously hampers plant quality and productivity. It is feasible to reduce or reverse the negative effects of salt through the supplementation of silicon (Si) and aspartic acid (Asp). However, the question of how exogenous Si and Asp induce salt tolerance in celery remains incipient. Thus, this study was performed to determine the synergistic effects of Si and Asp on the alleviation of salt stress in celery. To this end, the celery plants were cultivated in a controlled regime (light for 14 h at 22 °C; darkness for 10 h at 16 °C) and treated with one of five treatments (CK, 100 mM NaCl, 100 mM NaCl + 75 mg/L Si, 100 mM NaCl + 100 mg/L Asp, and 100 mM NaCl + 75 mg/L Si + 100 mg/L Asp). Results showed that solely NaCl-treated celery plants developed salt toxicity, as characterized by decreased growth, declined photosynthetic ability, disturbed nutritious status and internal ion balance, and a boosted antioxidant defense system (Improved antioxidant enzymes and reduced ROS accumulation). In contrast, these adverse effects of NaCl were ameliorated by the additions of Si and Asp, regardless of Si, Asp, or both. Moreover, the mitigatory impacts of the co-application of Si and Asp on salt stress were more pronounced compared to when one of them was solely applied. Collectively, exogenous Si and Asp alleviate the degree of salt stress and thereby improve the salt tolerance of celery.

The strawberry (Fragaria × ananassa Duch.) “Sulhyang” is a typical seasonal flowering (SF) strawberry that produces flower buds in day lengths shorter than a critical limit (variable, but often defined as CO, FT1, SOC1, and TFL1) participating in light signaling and circadian rhythm in plants are altered under blue light (BL). Sugars for flowering and runnering are mainly produced by photosynthetic carbon assimilation. The intensity of light could affect photosynthesis, thereby regulating flowering and runnering. Here, we investigated the effect of the intensity of supplemental blue light (S-BL) or night-interrupting blue light (NI-BL) in photoperiodic flowering and runnering regulation by applying 4 h of S-BL or NI-BL with either 0, 10, 20, 30, or 40 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) in a 10 h short-day (SD10) (SD10 + S-BL4 or + NI-BL4 (0, 10, 20, 30, or 40)) or 14 h long-day (LD14) conditions (LD14 + S-BL4 or + NI-BL4 (0, 10, 20, 30, or 40)). Approximately 45 days after the photoperiodic light treatment, generally, whether S-BL or NI-BL, BL (20) was the most promotive in runnering, leading to more runners in both the LD and SD conditions. For flowering, except the treatment LD14 + S-BL, BL (20) was still the key light, either from BL (20) or BL (40), promoting flowering, especially when BL acted as the night-interrupting light, regardless of the photoperiod. At the harvest stage, larger numbers of inflorescences and runners were observed in the LD14 + NI-BL4 treatment, and the most were observed in the LD14 + NI-BL (20). Moreover, the SD10 + NI-BL4 was slightly inferior to the LD14 + NI-BL4 in increasing the numbers of inflorescences and runners, but it caused earlier flowering. Additionally, the circadian rhythm expression of flowering-related genes was affected differently by the S-BL and NI-BL. After the application of BL in LD conditions, the expression of an LD-specific floral activator FaFT1 was stimulated, while that of a flowering suppressor FaTFL1 was inhibited, resetting the balance of expression between these two opposite flowering regulators. The SD runnering was caused by BL in non-runnering SD conditions associated with the stimulation of two key genes that regulate runner formation in the GA pathway, FaGRAS32 and FaGA20ox4. In addition, the positive effects of BL on enhancing photosynthesis and carbohydrate production also provided an abundant energy supply for the flowering and runnering processes.

Basil (Ocimum basilicum L.) contains abundant nutrients and is considered an economically important edible vegetable. The optimal nutrient levels will increase the productivity and basil quality. However, prominent research on basil regarding the diagnostic nutrient deficiency standard and the corresponding nutrient uptake is still scarce. To this end, the basil plants were hydroponically cultured and subjected to one of 14 nutrient solution treatments, corresponding to the omission of a single nutrient element (designated as -N, -P, -K, -Ca, -Mg, -NH4+, -NO3−, -S, -Fe, -Mn, -B, -Zn, -Mo, and -Cu) and a complete nutrient solution (CS) as the control. The most common nutrient deficiency symptoms were chlorosis, stunted roots and growth, and even leaf necrosis and abscission, in particular of -N, -P, -NO3−, and -Fe. We also found that basil is a NH4+-sensitive species. The photosynthetic capacity (photosynthesis pigments, Fv/Fm ratio, and greenness index) was disturbed to varying degrees when a single nutrient was omitted from the nutrient solution. Additionally, the omission of a specific single nutrient confers significant differences in the tissue nutrients, regardless of the macronutrients and micronutrients considered. Concomitantly, multivariate analysis suggested the correlations among certain important nutrients were distinctly different under different treatments (correlation analysis); the influences of different nutrient deficiencies on the tissue nutrient concentrations showed similarity (principal component analysis). Collectively, the growth, physiological, and biochemical changes studied in this trial not only improved our knowledge for diagnosing nutrient deficiency symptoms for practical cultivation but also provided a comprehensive understanding of the internal nutrient associations in basil.

Environmental (abiotic) stresses significantly threaten the worldwide crop production and food security. Rapid, drastic changes in the global climate have exacerbated such stresses for crops. Plant-associated bacteria have been shown to enhance stress resistance and cope with the negative impacts of various abiotic stresses through the induction of various mechanisms. In soil, the rhizosphere and endosphere of plants, the Bacillus genus is a predominant bacterial genus. Members of this genus, which are tremendously diverse both metabolically and genetically, survive for a long time under unfavorable environmental conditions due to their ability to form long-lived, stress-tolerant spores. Bacillus spp. secrete several metabolites that trigger plant growth and enhance plants’ tolerance to biotic and abiotic stresses. Some of the Bacillus species are available commercially as phytostimulants, biopesticides, and biofertilizers. Due to this functional versatility, the Bacillus genus is one of the most widely used in the agro-biotech industry. However, the potential of the Bacillus genus has not yet been sufficiently realized, and transferring technology related to the genus from the lab environment to real world applications in the field needs to be emphasized. A better understanding of mechanisms of action of beneficial Bacillus spp. is needed for the development of products to support green biotechnology in agriculture and industries. This report comprehensively reviews the applications of Bacillus spp. in abiotic (e.g., salinity, drought, inorganic and organic pollutant toxicity, nutritional imbalance, low–high temperatures, and waterlogging) -stressed agriculture and discusses their potentials for the development of new products of biotechnological implications, highlighting gaps that remain to be explored to improve and expand on Bacillus-based biostimulants.

Compared to the traditional production of ginseng roots, Panax ginseng sprouts (PGSs) are currently regarded as a substitute due to the relatively short-term culture but still high nutrition. However, the optimal light intensity for the growth ability of PGSs and the characterizations of the responses of PGSs to the light intensity have been largely neglected. This study aimed to determine the influences of the light intensity on the growth, morphogenesis, and photosynthetic responses in PGSs. To this end, two-year-old ginseng rootlets were subjected to one of six light intensities (from 30 to 280 PPFD with 50 PPFD intervals) in a plant factory with artificial lighting (PFAL) via LED light for 10 weeks. On the whole, the recorded parameters of the PGSs showed gradually decreasing trends in response to the increasing light intensities. However, the 80 PPFD-treated PGSs possessed similar or greater root dry weights, leaf areas, carotenoids levels, and photosynthesis (the maximal PSII quantum yield) compared to those in the 30 PPFD regime. Additionally, photoinhibition symptoms as evidenced by chlorosis, necrosis, and stunted growth were observed as the light intensity attained 180 PPFD. Thus, 130 PPFD could be considered a safe point for the appearance of photoinhibition in PGSs. Taken together, we show that the light intensity range of 30–80 PPFD is suitable for maximizing the production of PGSs in PFALs.

Nowadays, not only the roots, but also leaves and flowers of ginseng are increasingly popular ingredients in supplements for healthcare products and traditional medicine. The cultivation of the shade-loving crop, ginseng, is very demanding in terms of the light environment. Along with the intensity and duration, light direction is another important factor in regulating plant morphophysiology. In the current study, three lighting directions—top (T), side (S), or top + side (TS)—with an intensity of 30 ± 5 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) were employed. Generally, compared with the single T lighting, the composite lighting direction, TS, was more effective in shaping the ginseng with improved characteristics, including shortened, thick shoots; enlarged, thick leaves; more leaf trichomes; earlier flower bud formation; and enhanced photosynthesis. The single S light resulted in the worst growth parameters and strongly inhibited the flower bud formation, leading to the latest flower bud observation. Additionally, the S lighting acted as a positive factor in increasing the leaf thickness and number of trichomes on the leaf adaxial surface. However, the participation of the T lighting weakened these traits. Overall, the TS lighting was the optimal direction for improving the growth and development traits in ginseng. This preliminary research may provide new ideas and orientations in ginseng cultivation lodging resistance and improving the supply of ginseng roots, leaves, and flowers to the market.

The photoreceptor-mediated photoperiodic sensitivity determines the obligate short-day flowering in chrysanthemum (Chrysanthemum morifolium Ramat.) when the night length is longer than a critical minimum, otherwise, flowering is effectively inhibited. The reversal of this inhibition by subsequent exposure to a short period of supplemental (S) or night-interruptional (NI) blue (B) light (S-B; NI-B) indicates the involvement of B light-received photoreceptors in the flowering response. Flowering is mainly powered by sugars produced through photosynthetic carbon assimilation. Thus, the light intensity can be involved in flowering regulation by affecting photosynthesis. Here, it is elucidated that the intensity of S-B or NI-B in photoperiodic flowering regulation of chrysanthemums by applying 4-h of S-B or NI-B with either 0, 10, 20, 30, or 40 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) in a 10-h short-day (SD10) [SD10 + 4B or + NI-4B (0, 10, 20, 30, or 40)] or 13-h long-day (LD13) condition [LD13 + 4B or + NI-4B (0, 10, 20, 30, or 40)] provided by 300 ± 5 μmol·m−2·s−1 PPFD white (W) LEDs. After 60 days of photoperiodic light treatments other than the LD13 and LD13 + NI-4B (40), flowering with varying degrees was observed, although the SD10 gave the earliest flowering. And the LD13 + 4B (30) produced the greatest number of flowers. The flowering pattern in response to the intensity of S-B or NI-B was consistent as it was gradually promoted from 10 to 30 μmol m−2 s−1 PPFD and inhibited by 40B regardless of the photoperiod. In SD conditions, the same intensity of S-B and NI-B did not significantly affect flowering, while differential flowering inhibition was observed with any intensity of NI-B in LDs. Furthermore, the 30 μmol·m−2·s−1 PPFD of S-B or NI-B up-regulated the expression of floral meristem identity or florigen genes, as well as the chlorophyll content, photosynthetic efficiency, and carbohydrate accumulation. The 40B also promoted these physiological traits but led to the unbalanced expression of florigen or anti-florigen genes. Overall, the photoperiodic flowering in response to the intensity of S-B or NI-B of the SDP chrysanthemum suggests the co-regulation of photosynthetic carbon assimilation and differential photoreceptor-mediated control.

Panax ginseng sprouts (PGS) have the advantage of requiring short-term cultivation while maintaining higher ginsenoside contents than traditional ginseng seedlings. It is feasible to improve their yield capacity by manipulating physical factors such as temperature and light. This study therefore investigated the effects of the DIF (difference between day and night temperature) and LI (light intensity) on the growth and photosynthetic characteristics of PGS. To this end, four DIF treatments (18/22 °C, 20/20 °C, 22/22 °C, 22/18 °C), corresponding to two LI regimes (20 PPFD, 200 PPFD), were applied on one-year-old ginseng rootlets in closed-type plant production systems (CPPSs). The PGS had distinctly different responses to the eight treatments. In particular, we found that negative DIF considerably hampered the growth and development of roots, shoots, leaves, and photosynthesis, regardless of the LI considered. The PGS treated with 20/20 °C combined with 20 PPFD displayed the best root growth, shoot development, leaf area, as well as optimal photosynthetic ability. On the other hand, we further showed that the root growth rate was positively correlated with the stem diameter, leaf traits, and photosynthetic ability, whereas it was negatively correlated with the petiole length, stem length, and shoot length. Collectively, 20/20 °C combined with 20 PPFD was the optimal condition in the current study, and may be regarded as a successful strategy for large-scale productions of PGS.

Ammonium sensitivity is considered a globally stressful condition that affects overall crop productivity. The major toxic symptom associated with ammonium nutrition is growth retardation, which has been associated with a high energy cost for maintaining ion, pH, and hormone homeostasis and, eventually, the NH3/NH4+ level in plant tissues. While certain species/genotypes exhibit extreme sensitivity to ammonium, other species/genotypes prefer ammonium to nitrate as a form of nitrogen. Some of the key tolerance mechanisms used by the plant to deal with NH4+ toxicity include an enhanced activity of an alternative oxidase pathway in mitochondria, greater NH4+ assimilation plus the retention of the minimum level of NH4+ in leaves, and/or poor response to extrinsic acidification or pH drop. Except for toxicity, ammonium can be considered as an energy-efficient nutrition in comparison to nitrate since it is already in a reduced form for use in amino acid metabolism. Through effective manipulation of the NH4+/NO3 − ratio, ammonium nutrition can be used to increase productivity, quality, and resistance to various biotic and abiotic stresses of crops. This review highlights recent advancements in ammonium toxicity and tolerance mechanisms, possible strategies to improve ammonium tolerance, and omics-based understanding of nitrogen use efficiency (NUE) in plants.

Petunia hybrida Hort. “Easy Wave Pink”, a qualitative long-day plant (LDP), was investigated to study the effects of the night interruption light (NIL) provided by light-emitting diodes (LEDs) quality shifting on the morphogenesis, blooming, and transcription of photoreceptor genes. Plants were grown in a closed-type plant factory employing white (W) LEDs at an intensity of 180 μmol·m−2·s−1 PPFD provided for short day (SD, 10 h light, 14 h dark), long day (LD, 16 h light, 8 h dark), or SD with 4 h night interruption (NI) with LEDs at an intensity of 10 μmol·m−2·s−1 PPFD. The NIL quality was shifted from one light spectrum to another after the first 2 h of NI. Light treatments consisting of all possible pairings of W, far-red (Fr), red (R), and blue (B) light were tested. The SD and LD were referenced as the control, while 12 NI treatments involved altering LED NIL qualities, as follows: from R to B (NI-RB), from B to R (NI-BR), from Fr to R (NI-FrR), from R to Fr (NI-RFr), from Fr to B (NI-FrB), from B to Fr (NI-BFr), from B to W (NI-BW), from W to B (NI-WB), from W to Fr (NI-WFr), from Fr to W (NI-FrW), from W to R (NI-WR), and from R to W (NI-RW). The NI-RFr resulted in the longest shoots, while the NI-WR and NI-RW resulted in the shortest shoots. NI-WR, NI-RW, NI-BW, NI-WB, NI-RFr, NI-RB, NI-BR, and LD all exhibited flowering. High-level expressions of photoreceptor genes were confirmed in the NI-RFr, NI-FrR, NI-BFr, NI-RW, and NI-WR treatments. Morphogenesis and blooming were both impacted by the photoperiod. The first NIL had no effects on the flowering or the morphogenesis, but the second NIL had a profound impact on both.

Silicon (Si) has been reported to benefit plant growth and stress resistance. This work aimed to find out an optimal method of Si application to enhance the resistance of strawberry (Fragaria × ananassa Duch.) transplants to high temperatures, commonly experienced in the summer when strawberries are propagated for greenhouse production in Korea. Plants of strawberry “Sulhyang”, “Maehyang”, and “Kuemsil” were subjected to one of five treatments before the cutting propagation: no treatment (control), substrate dressing of a water-soluble silicate fertilizer, substrate drench of 75 mg·L−1 Si (from potassium silicate) to the mother plants, or foliar spray of 75 mg·L−1 Si to either the mother plants or daughter plants. Half of the daughter plants in each Si treatment received continued application of Si through either substrate dressing of a water-soluble silicate fertilizer, substrate drench, or foliar spray after the cutting propagation. A high temperature (43°C) resistance test was conducted in plant growth chambers for 7 days with a 16-h photoperiod with a light intensity of 300 mmol·m−2·s−1 PPFD. During the high temperature test, the rate of decline in the photosynthesis was lower in plants treated with Si than in the control. After the high temperature test, it was observed that Si application significantly increased the shoot fresh weight of transplants. Moreover, the contents of sugars, proteins, and enzymatic (CAT, SOD, POD, and APX) and non-enzymatic (anthocyanin and proline) antioxidants were higher in plants treated with Si throughout the entire propagation period, compared to the control and plants only treated with Si before or after the cutting propagation. Overall, the Si application improved the growth of the transplants regardless of the application method used. Moreover, spraying the daughter plants with Si, and continually spraying the transplants were found to be the best and is recommended to increase the resistance of strawberries to high temperatures during propagation.

Ammonium (NH4+) toxicity hinders the cabbage yield because most subspecies or varieties exhibit extreme sensitivity to NH4+. Current knowledge indicates that silicon (Si) can alleviate or reverse the ammonium toxicity severity. However, few investigations have been conducted on NH4+-stressed cabbage to elucidate the mechanism underlying the Si alleviation. The study described herein analyzes induced physio-chemical changes to explore how Si helps mitigate NH4+ toxicity. We applied one of three NH4+:NO3- ratios (0:100, 50:50, and 100:0) at a constant N (13 meq·L−1) to the cabbage plants, corresponding with two Si treatment levels (0 and 1.0 meq·L−1). Chlorosis and foliage necrosis along with stunted roots occurred following 100% NH4+ application were ameliorated in the presence of Si. The NH4+ toxicity ratio was reduced accordingly. Similarly, inhibition on the uptake of K and Ca, restricted photosynthesis (chlorophyll, stomatal conductance, and Fv/Fm), and accumulation of reactive oxygen species (ROS, O2·-, and H2O2), as well as lipid peroxidation (MDA, malondialdehyde) in NH4+-stressed cabbages were mitigated with added Si. The lower observed oxidative stresses in solely NH4+-treated plants were conferred by the boosted antioxidant enzymes (SOD, superoxide dismutase; CAT, catalase). Concomitantly, Si-treated plants showed higher activities of key NH4+ assimilation enzymes (GS, glutamine synthetase; GOGAT, glutamate synthase; NADH-GDH, glutamate dehydrogenase) and NH4+ content in leaves. However, excessive NH4+ assimilations cause the acidic stress, which has been demonstrated to be the primary cause of NH4+ toxicity. Therefore, further investigation regarding the Si effects on H+ regulation and distribution should be warranted.

Seleno-amino acids are safe, health-promoting compounds for humans. Numerous studies have focused on the forms and metabolism of seleno-amino acids in vegetables. Based on research progress on seleno-amino acids, we provide insights into the production of selenium-enriched vegetables with high seleno-amino acids contents. To ensure safe and effective intake of selenium, several issues need to be addressed, including (1) how to improve the accumulation of seleno-amino acids and (2) how to control the total selenium and seleno-amino acids contents in vegetables. The combined use of plant factories with artificial lighting and multiple analytical technologies may help to resolve these issues. Moreover, we propose a Precise Control of Selenium Content production system, which has the potential to produce vegetables with specified amounts of selenium and high proportions of seleno-amino acids.

This study examines how the day neutral plant (DNP) Pelargonium × hortorum L.H. Bailey ‘Ringo 2000 Violet’ is impacted by LED night-interruption light (NIL) quality shifting in terms of flowering, morphogenesis, and transcription of photoreceptor genes. A closed-type plant factory with white (W) LEDs providing 180 μmol·m−2·s−1 PPFD light for long day (LD, 16 h light, 8 h dark), short day (SD, 10 h light, 14 h dark), or SD with 4 h night interruption (NI) with 10 μmol·m−2·s−1 PPFD LEDs was used to grow the plants. Two NIL qualities were employed, where after the first two hours, the NIL quality was switched from one to another among white (W), far-red (Fr), red (R), and blue (B). A total of 12 SD treatments with NIL quality shifting were used, with the LD and SD serving as the control: NI-BR (from B to R), NI-RB (from R to B), NI-RFr (from R to Fr), NI-FrR (from Fr to R), NI-BFr (from B to Fr), NI-FrB (from Fr to B), NI-WB (from W to B), NI-BW (from B to W), NI-FrW (from Fr to W), NI-WFr (from W to Fr), NI-RW (from R to W), and NI-WR (from W to R). LD refers to a 16 h long-day treatment. Geranium plants were taller in NI treatments that included Fr light than those in other NI treatments and were the shortest in the NI-WB treatment. Flowering was seen in all treatments and was notably encouraged by NI with Fr light, regardless of the sequence of light quality applied. In NI-FrR and NI-RFr, high expressions of phyA, phyB, and cry1 were observed. Flower formation and plant morphogenesis were both impacted by the photoperiod. Both morphogenesis and flowering were strongly impacted by the second NIL, but the first NIL had no effects on either. These findings indicate that NI-RFr and NI-FrR improve flowering, which may be used for commercial DNP production.

The flowering of chrysanthemum (Chrysanthemum morifolium Ramat.), inhibited by long-day lighting, can be reversed with a short period of low supplemental blue light (S-BL). Both flowering and the reactive oxygen species (ROS) scavenging processes are primarily driven by sugars created by photosynthetic carbon assimilation. In addition, the antioxidant ability potentially affects flowering in photoperiod- and/or circadian rhythm-dependent manners. This indicates that there is an interactive relationship among blue (B) light, photosynthetic efficiency, sugar accumulation, and antioxidant ability in flowering regulation. Here, 4 h of 30 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) S-BL was applied at the end of a 13-h long-day period (LD13 + 4B) at different intervals during 60 days of experimental duration. The five experimental groups were named according to the actual number of days of S-BL and their intervals: applied once every day, “60 days-(LD13 + 4B) (100.0%)”; once every other day, “30 days-(LD13 + 4B) (50.0%)”; once every three days, “15 days-(LD13 + 4B) (25.0%)”; once every five days, “10 days-(LD13 + 4B) (16.7%)”; and once every seven days, “7 days-(LD13 + 4B) (11.7%)”. Two non-S-BL control groups were also included: 60 10-h short days (60 days-SD10) and 13-h long days (60 days-LD13). At the harvest stage, varying degrees of flowering were observed except in “60 days-LD13” and “7 days-(LD13 + 4B) (11.7%)”. The number of flowers increased and the flower buds appeared earlier as the proportion of S-BL days increased in LD13 conditions, although the “60 days-SD10” gave the earliest flowering. The proportion of initial, pivotal, and optimal flowering was 16.7% (“10 days-(LD13 + 4B)”), 50.0% (“30 days-(LD13 + 4B)”), and 100.0% (“60 days-(LD13 + 4B)”), respectively. Meanwhile, a series of physiological parameters such as the production of enzymatic or non-enzymatic antioxidants, chlorophyll content, photosynthetic efficiency, enzyme activities, and carbohydrate accumulation were significantly improved by “30 days-(LD13 + 4B) (50.0%)” as a turning point until the peaks appeared in “60 days-(LD13 + 4B) (100.0%)”, as well as the expression of florigenic or anti-florigenic and some antioxidant-synthetic genes. Furthermore, the results of principal component analysis (PCA) indicated that S-BL days positively regulated flowering, photosynthesis, carbohydrate accumulation, and antioxidant production. In aggregate, the pivotal and optimal proportions of S-BL days to reconcile the relationship among flowering, photosynthetic carbon assimilation, and antioxidant ability were 50.0% and 100.0%, respectively. However, there are still significant gaps to be filled in order to determine the specific involvement of blue light and antioxidant abilities in flowering regulation.

Ssamchoo is recently attracting attention as a household hydroponic vegetable in Korea. It has a refreshing texture and a rich content of vitamins and fiber. Ssamchoo with a wide leaf area is suitable for traditional ssam or vegetable wraps, as well as a vegetable for salads; thus, it can be used in a variety of dishes. However, Ssamchoo plants responds sensitively to the nutrient solution, and it is often difficult to secure sufficient leaf area and robust growth using a commercial nutrient solution for leafy vegetables. This study consisted of three experiments conducted to develop the nutrient solution for Ssamchoo grown in a newly developed home hydroponic cultivation system using light-emitting diodes as the sole source of light. In the first experiment, growth and development of Ssamchoo in a representative commercial nutrient solution, Peters Professional (20-20-20, The Scotts Co., Marysville, OH, USA), was compared with laboratory-prepared nutrient solutions, GNU1 and GNU2. As a result, the Ssamchoo grown in Peters Professional had a high NH4+ content in the tissue, leaf yellowing, darkened root color, and suppressed root hair development. In addition, adverse effects of ammonium such as low fresh weight and shorter shoot length were observed. In the second experiment, Peters Professional was excluded, and the ratio of NO3− to NH4+ in the GNU1 and GNU2 nutrient solutions was set to four levels each (100:0, 83.3:16.7, 66.7:33.3, and 50:50). As a result, the fresh weights of 83.3:16.7 and 66.7:33.3 were the greatest, and the leaf color was a healthy green. However, at 100:0 and 50:50 NO3−/NH4+ ratios, the fresh weight was low, and leaf yellowing, tip burn, and leaf burn appeared. The nutrient solution with a 83.3:16.7 NO3−- to-NH4+ ratio, which gave the greatest fresh weight in the second experiment, was chosen as the control, while the solution with a 50:50 NO3−/NH4+ ratio with a lower nitrate content among the two unfavorable treatments was selected as a treatment group for the next experiment. In the third experiment, NH4+ was partially replaced with urea to make four different ratios of NO3− to NH4+ to urea (83:17:0, 50:50:0, 50:25:25, and 50:0:50) in combination with two levels of Si (0 and 10.7 mmol·L−1 Si). The greatest fresh weight was obtained in the treatment in which the NO3−/NH4+/urea ratio was 50:25:25. In particular, when Si was added to the solution, there was no decrease in the number of leaves, and plants with the greatest fresh weight, chlorophyll content, and leaf area were obtained. The number of leaves and leaf area are important indicators of high productivity since the Ssamchoo is used in ssam dishes. It can be concluded that a solution with a NO3−/NH4+/urea ratio of 50:25:25 and supplemented with 10.7 mmol·L−1 Si is the most suitable nutrient solution for growing Ssamchoo in the home hydroponic system developed.

The ornamental plant Cotoneaster wilsonii Nakai is a rare endemic species to the Ulleung Island in Korea. There is an urgent need to develop efficient propagation methods to preserve this endangered plant species. The cytokinin thidiazuron (TDZ) at a concentration of 0, 1.0, 2.0, or 3.0 mg·L−1 combined with 0, 0.5, 1.0, or 1.5 mg·L−1 a-naphthaleneacetic acid (NAA) was used to induce calli from young leaf explants on the Murashige and Skoog (MS) medium. The TDZ and/or 6-benzyladenine at a concentration of 0, 0.5, or 1.0 mg·L−1 combined with 0.2 mg·L−1 NAA was supplied to the MS medium to induce shoots from calli. Four auxins at 0, 0.2, 0.4, 0.6, 0.8, or 1.0 mg·L−1 were supplied to half-strength MS medium for root induction. The treatment of TDZ at 1.0 mg·L−1 combined with 1.5 mg·L−1 NAA not only had 100% callus induction ratio, but also induced the heaviest calli. The shoot induction ratio was the greatest with TDZ at 1.0 mg·L−1, and the greatest root induction ratio was obtained with IAA at a concentration of 0.8 mg·L−1. In conclusion, an effective indirect organogenesis system was established for C. wilsonii Nakai.

Ammonium (NH4+) toxicity seriously hampers the yield and quality of salvia plants because most varieties or sub-species are highly sensitive to NH4+. Silicon (Si) is an alternative that is used to minimize these disturbances and maintain better growth under NH4+ toxicity. Nevertheless, the mitigatory effects of Si on NH4+-stressed salvia are unknown. Therefore, this study was carried out to determine how Si assists to alleviate the NH4+ toxicity degree in salvia. To this end, salvia plants were cultivated in a controlled environment supplied with a constant N (nitrogen) level (13 meq·L−1) in the form of three NH4+:NO3− ratios (0:100, 50:50, 100:0), each with (1.0 meq·L−1) or without Si. Physiological disorders and typical NH4+ toxicity symptoms, as well as interrupted photosynthesis, were observed in the 100% NH4+-treated plants. Furthermore, cation uptake inhibition and oxidative damage were also imposed by the 100% NH4+ supply. In contrast, in the presence of Si, the NH4+ toxicity degree was attenuated and plant growth was ensured. Accordingly, the NH4+ toxicity appearance ratio decreased significantly. Furthermore, Si-treated plants showed an ameliorated photosynthetic ability, elevated internal K and Ca levels, and enhanced antioxidative capacity, as reflected by improved major antioxidant enzyme activities, as well as diminished accumulation of ROS (reactive oxygen species) and MDA (malondialdehyde). Our findings enlightened the agronomic importance of additional Si to nutrient solutions, especially pertaining to bedding plants at risk of NH4+ toxicity.

Phosphorus (P) availability is usually low in soils around the globe. Most soils have a deficiency of available P; if they are not fertilized, they will not be able to satisfy the P requirement of plants. P fertilization is generally recommended to manage soil P deficiency; however, the low efficacy of P fertilizers in acidic and in calcareous soils restricts P availability. Moreover, the overuse of P fertilizers is a cause of significant environmental concerns. However, the use of arbuscular mycorrhizal fungi (AMF), phosphate–solubilizing bacteria (PSB), and the addition of silicon (Si) are effective and economical ways to improve the availability and efficacy of P. In this review the contributions of Si, PSB, and AMF in improving the P availability is discussed. Based on what is known about them, the combined strategy of using Si along with AMF and PSB may be highly useful in improving the P availability and as a result, its uptake by plants compared to using either of them alone. A better understanding how the two microorganism groups and Si interact is crucial to preserving soil fertility and improving the economic and environmental sustainability of crop production in P deficient soils. This review summarizes and discusses the current knowledge concerning the interactions among AMF, PSB, and Si in enhancing P availability and its uptake by plants in sustainable agriculture.

The current study has determined the effect of red and blue lights on the enhancement of growth, antioxidant property, phytochemical contents, and expression of proteins in Scrophularia kakudensis. In vitro-grown shoot tip explants of S. kakudensis were cultured on the plant growth regulator-free Murashige and Skoog (MS) medium and cultured under the conventional cool white fluorescent lamp (control), blue light-emitting diodes (LED) light, or red LED light. After 4 weeks, growth, stomatal ultrastructure, total phenols and flavonoids, activities of antioxidant enzymes, and protein expressions were determined. Interestingly, blue or red LED treatment increased the shoot length, shoot diameter, root length, and biomass on comparison with the control. In addition, the LED treatments enhanced the contents of phytochemicals in the extracts. The red LED treatment significantly elicited the accumulation of flavonoids in comparison with the control. In accordance with the secondary metabolites, the LED treatments modulated the activities of antioxidant enzymes. Moreover, the proteomic insights using two-dimensional gel electrophoresis system revealed the proteins involved in transcription and translation, carbohydrate mechanism, post-translational modification, and stress responses. Taken together, the incorporation of blue or red LED during in vitro propagation of S. kakudensis can be a beneficial way to increase the plant quality and medicinal values of S. kakudensis.

Kalanchoe (Kalanchoe blossfeldiana) is a qualitative short-day plant with a high aesthetic value. When the night length is less than a specified cultivar-dependent critical value, however, it does not develop flowers. This study investigated the effects of low-intensity supplementary or night interrupting (NI) blue (B) light on the plant performance and flower induction in kalanchoe ‘Rudak’. During the photoperiod in a closed-type plant factory with day/night temperatures of 23 °C/18 °C, white (W) LEDs were utilized to produce a photosynthetic photon flux density (PPFD) of 300 μmol m−2 s−1, and B LEDs were used to give supplementary/NI light at a PPFD of 10 μmol m−2 s−1. The control plants were exposed to a 10-h short day (SD, positive control) or a 13-h long day (LD, negative control) treatment without any B light. The B light was used for 4 h either (1) to supplement the W LEDs at the end of the SD (SD + 4B) and LD (LD + 4B), or (2) to provide night interruption (NI) in the SD (SD + NI-4B) and LD (LD + NI-4B). The LD + 4B and LD + NI-4B significantly enhanced plant growth and development, followed by the SD + 4B and SD + NI-4B treatments. In addition, the photosynthesis, physiological parameters, and activity of antioxidant systems were improved in those treatments. Except in the LD and LD + NI-4B, all plants flowered. It is noteworthy that kalanchoe ‘Rudak’ flowered in the LD + 4B treatment and induced the greatest number of flowers, followed by SD + NI-4B and SD + 4B. Plants grown in the LD + 4B treatment had the highest expression levels of certain monitored genes related to flowering. The results indicate that a 4-h supplementation of B light during the photoperiod in both the SD and LD treatments increased flower bud formation, promoted flowering, and enhanced plant performance. Kalanchoe ‘Rudak’ flowered especially well in the LD + 4B, presenting a possibility of practically inducing flowering in long-day seasons with B light application.

The ammonium (NH4+) tolerance of plants is an important issue in agriculture, associated with several plant characteristics. So far, plant tissue acidification has been shown as the primary cause of NH4+ toxicity. Suppressed plant growth caused by excess NH4+ can be counteracted by potassium (K+) application. However, the effects of NH4+ tolerances on the differences regarding pH changes together with K+ uptake remain to be determined. Here, we performed an 84 h hydroponic cultivation of five species with different NH4+ tolerances, subjected to three NH4+:NO3− solutions (0:100, 50:50, or 100:0), to investigate the pH changes and ion uptakes. Consequently, the solution pH was lowered over time to varying extents in the presence of NH4+. The NH4+-tolerant ageratum and lettuce, shown to be tolerant to NH4+ in this trial, rapidly lowered the solution pH, whereas extremely NH4+-sensitive salvia and cabbage only gave a minor decrease in the solution pH when grown with 100:0 NH4+:NO3−. Additionally, the increased external NH4+ level led to a substantial decline in the net cation influxes (K+, Ca2+, and Mg2+). As compared to solely NH4+-fed salvia and cabbage, solely NH4+-fed ageratum and lettuce ultimately showed a relatively greater net K+ influx. Taken together, this study discusses how the decreases in pH and K+ are related to NH4+ tolerance in five hydroponically cultured species.

Two cut rose (Rosa hybrida) cultivars ‘Sherbet’ (easy-to-root) and ‘Alibaba’ (difficult-to-root) were propagated by single nodal cuttings on preformed media. Four commercial media such as Tosilee, Ellepot, rockwool and phenolic foam RC, and four newly-developed foam media namely Oasis PU 14-S1, Oasis TP-S1, Oasis PU-7B and Oasis PU 15-S1 were employed in this study. All media were manufactured to fit into 50-cell plug trays. The experiment was laid out in a complete randomized block design with three replications on a propagation bench with a plastic tunnel installed in a glasshouse, with (98 ± 2)% relative humidity and over 50% shading of the natural sunlight. After four weeks of experiment, growth parameters, localization of superoxide radicals, and activities of rooting biochemical markers were measured. The results suggested that the newly-developed foam media Oasis TP-S1 and Oasis PU-7B enhanced the growth, density of leaf stomata, and consisted of lesser harmful superoxide radicals in similar manner with the existing commercial media. Moreover, the Oasis TP-S1 and Oasis PU-7B media significantly enhanced the total phenol content and the activities of important enzymes involved in the phenol metabolism which plays a vital role in the formation of roots. Thus, the understanding of both physiological and biochemical changes implicated by the growing medium during the rooting of cuttings would aid in the selection of optimal growing medium for the propagation of rose cuttings. Keywords: foam medium, peroxidase, phenol, phenylalanine ammonia lyase (PAL), superoxide localization

Cnidium officinale Makino, a perennial herb of the family Umbelliferae, is a well-known medicinal plant in oriental medicine with antidiabetic, tumor metastatic, antiplatelet, antimicrobial and insecticidal properties. Hence, C. officinale does not produce seed the plant tissue culture is the viable alternative for its propagation. Node explant from in vitro grown C. officinale Makino was cultured on MS medium supplemented with plant growth regulators (PGRs) like 2,4-Dichlorophenoxyacetic acid (2,4-D) or/and 6-Benzylaminopurine (BA). It was aimed to investigate the optimal concentration and combination of 2,4-D and BA for somatic embryogenesis in node explant of C. officinale Makino. The embryogenic callus was induced on node explant after four weeks in MS medium containing 1.5 mg L−1 2,4-D and 0.5 mg L−1 BA. The translucent white, embryogenic callus was subcultured on the respective medium and individual well-structured somatic embryos were observed. Heart and cotyledon stage embryos were pictured under a stereomicroscope. The individual somatic embryos (SE) were transferred to MS medium without PGRs (MS0) and 100% germination was observed. Repeated subculturing of the embryogenic callus for five months resulted in recurrent somatic embryogenesis but with a gradual decline in number.

Plants grow better when they are supplied with a combination of ammonium (NH4+) and nitrate (NO3−) than when either one is supplied as the sole N (nitrogen) source. However, the effects of N forms on N metabolism and major N assimilation enzymes in different plants, especially vegetables, are largely neglected. This study was conducted on two plants with distinct NH4+ tolerances to compare the responses of two popular leafy vegetables, Korean cabbage (Brassica campestris L.) ‘Ssamchu’ and lettuce (Lactuca sativa L.) ‘Caesar green’, to the N source. To this end, plant growth and quality, photosynthesis, carbohydrate, N contents (in the forms of NO3−, NO2−, NH4+, total protein), and key N assimilation-related enzyme (NR, NIR, GS, GDH) activities were investigated. When plants were subjected to one of three NH4+:NO3− regimes, 0:100, 50:50, or 100:0, lettuce was relatively more tolerant while cabbage was extremely sensitive to high NH4+. Both plants benefited more from being grown with 50:50 NH4+:NO3−, as evidenced by the best growth performance, ameliorated photosynthesis, and enriched carbohydrate (C) stock content. In addition, as compared to cabbage, the GS and GDH activities were reinforced in lettuce in response to an increasing external NH4+ level, resulting in low NH4+ accumulation. Our findings suggested that boosting or maintaining high GS and GDH activities is an important strategy for the ammonium tolerance in vegetables.

The significant effects of lighting on plants have been extensively investigated, but research has rarely studied the impact of different lighting directions for the strawberry plant. To understand the optimal lighting direction for better growth and development, this study investigated how strawberries respond to variations in the lighting direction to help fine-tune the growth environment for their development. We examined how the lighting direction affects plant morphophysiology by investigating plant growth parameters, leaf anatomy, epidermal cell elongation, stomatal properties, physiological characteristics, and expressions of runner induction-related genes (FaSOC1 and FaTFL1) and gibberellin (GA) biosyntheses-related genes (FaGA20ox2 and FaGA20ox4). In closed-type plant factory units, the rooted cuttings of strawberry (Fragaria × ananassa Duch.) ‘Suhlyang’ were subjected to a 10-h photoperiod with a 350 μmol∙m−2∙s−1 photosynthetic photon flux density (PPFD) provided by light-emitting diodes (LEDs) from three directions relative to the plants: top, side, and bottom. Our results demonstrated that the side lighting profoundly promoted not only morphophysiology, but also runner formation, by upregulating photosynthesis in strawberries. Side lighting can bring commercial benefits, which include reduced economic costs, easier controllability, and harmlessness to plants. This will help provide new insights for the propagation of the most commonly cultivated strawberries in South Korea.

Hydrangea macrophylla is a popular perennial ornamental shrub commercially grown as potted plants, landscape plants, and cut flowers. In the process of reproduction and production of ornamental plants, the absorption of nutrients directly determines the value of the ornamental plants. Hydrangea macrophylla is very sensitive to the content and absorption of the micronutrient iron (Fe) that affects growth of its shoots. However, the physiological activity of Fe as affected by deficiency or supplementation is unknown. This work aimed at preliminary exploring the relationship between Fe and photosynthesis, and also to find the most favorable iron source and level of pH for the growth of H. macrophylla. Two Fe sources, non-chelated iron sulfate (FeSO4) and iron ethylenediaminetetraacetic acid (Fe-EDTA), were supplemented to the multipurpose medium with a final Fe concentration of 2.78 mg·L−1. The medium without any Fe supplementation was used as the control. The pH of the agar-solidified medium was adjusted to either 4.70, 5.70, or 6.70, before autoclaving. The experiment was conducted in a culture room for 60 days with 25/18 °C day and night temperatures, and a 16-hour photoperiod provided at a light intensity of 50 mmol·m−2·s−1 photosynthetic photon flux density (PPFD) from white light-emitting diodes. Supplementary Fe increased the tissue Fe content, and leaves were greener with the medium pH of 4.70, regardless of the Fe source. Compared to the control, the number of leaves for plantlets treated with FeSO4 and Fe-EDTA were 2.0 and 1.5 times greater, respectively. The chlorophyll, macronutrient, and micronutrient contents were the greatest with Fe-EDTA at pH 4.70. Furthermore, the Fe in the leaf affected the photosynthesis by regulating stomata development, pigment content, and antioxidant system, and also by adjusting the expression of genes related to Fe absorption, transport, and redistribution. Supplementation of Fe in a form chelated with EDTA along with a medium pH of 4.70 was found to be the best for the growth and development of H. macrophylla plantlets cultured in vitro.

A hydroponic cultivation system was established to improve the nutraceutical properties of Ligularia fischeri (Ledeb.) Turcz, during which nutrient uptake by the plant from nutrient solution was measured using inductive coupled plasma-atomic emission spectroscopy (ICP-AES). Based on the obtained data, the uptake of macro and micro elements per gram of fresh weight was calculated. The uptake of macro-elements of NH4+-N, NO3−-N, K, S, P, Ca, and Mg were 1.62, 4.27, 8.41, 1.19, 2.59, 2.79, and 0.84 mg·g−1 FW and micro-elements of B, Fe, Mn, Mo, Cu, and Zn were 9.91, 22.31, 25.73, 2.51, 2.91, and 5.07 µg·g−1 FW. Moreover, the effects of cultivation systems on growth and phytochemical composition of L. fischeri were compared. The greatest biomass was observed in the hydroponic cultivation system with continuous circulation nutrient solution compared to natural soil and Tosilee media based culture systems. The recirculated hydroponic system significantly increased the total phenol contents of the leaf, petiole, and root extracts by 17.6%, 30.6%, and 20.9% more compared to the soil grown. The recirculated hydroponic system treatment significantly increased the total antioxidant capacity of root extracts by 55.9% more compared to the soil treatment. Based on the contents of elements, total phenolic and flavonoid, it was concluded that hydroponic cultivation system is the optimal method to enhance medicinal value. Keywords: Ligularia fischeri, hydroponic culture, micronutrient, macronutrient, phytochemical

The optimal photoperiod and light quality for runner induction in strawberries ‘Sulhyang’ and ‘Maehyang’ were investigated. Two experiments were carried out in a semi-closed walk-in growth chamber with 25/15 °C day/night temperatures and a light intensity of 250 μmol·m–2·s–1photosynthetic photon flux density (PPFD) provided from white light-emitting diodes (LEDs). In the first experiment, plants were treated with a photoperiod of either 12, 14, 16, 18, 20, or 22 h In the second experiment, a total of 4 h of night interruption (NI) light at an intensity of 70 μmol·m–2·s–1PPFD provided from either red, blue, green, white, or far-red LED in addition to 11 h short day (SD). The results showed that both ‘Sulhyang’ and ‘Maehyang’ produced runners when a photoperiod was longer than 16 h, and the number of runners induced positively correlated with the length of photoperiod. However, the plant growth, contents of chlorophyll, sugar and starch, and Fv/Fo decreased in a 22 h photoperiod. All qualities of the NI light, especially red light, significantly increased the number of runners and daughter plants induced per plant as compared with those in the SD treatment in both cultivars. In a conclusion, a photoperiod between 16 and 20 h and NI light, especially red NI light, can be used for quality runner induction in both ‘Sulhyang’ and ‘Maehyang’.

Dendrobium aphyllum (Roxb.) C. E. Fischer is an ornamental plant with certain medicinal values from the Orchidaceae family. Currently, micropropagation is the main means through which it is propagated. In this research, the effects of different daytime and nighttime temperatures (DIF) and medium supplementation with rare earth elements (REE) on the growth and metabolism of D. aphyllum during a micropropagation period were investigated. Three kinds of REE nitrates, La(NO₃)₃, Ce(NO₃)₃ and Nd(NO₃)₃, at four concentrations, 50, 100, 150, and 200 μM, were added to the culture medium. Three DIFs, 0, 6 and 12 °C, with an identical mean daily temperature of 20 °C, were used with photoperiod/dark period temperatures of 20/20 °C, 23/17 °C and 26/14 °C, respectively. After four weeks of culture, both supplemental REE and DIF treatments promoted growth of the plant compared with the control group. With increased REE concentration and DIF, the growth of the plants was suppressed and symptoms of stress response occurred. At the same concentration, Ce(NO₃)₃ had a more significant promotional effect on plant growth. In general, the medium supplemented with 100 μM Ce(NO₃)₃ combined with a 6 °C DIF was the most optimal for the vegetative growth of the plant. A 12 °C DIF promoted synthesis of more primary metabolites such as total proteins and polysaccharides. From the perspective of improving the medicinal values of this plant, increasing the DIF for an optimal growth environment is a valuable reference. This study can provide a technical basis for the propagation and production of Dendrobium aphyllum in the future.

Peony is an important ornamental plant and has become increasingly popular for cut flower cultivation. However, a short vase life and frequent poor vase quality severely restrict its market value. The study described herein was conducted to investigate the effects of silicon application on the vase life and quality of two cut peony (Paeonia lactiflora Pall.) cultivars, ‘Taebaek’ and ‘Euiseong’. For pre- and/or postharvest silicon application, four experimental groups based on treatments were designed. With silicon treatment, the relevant growth attributes, including the shoot and leaf lengths, stem and bud diameters as well as the leaf width were all remarkably increased. In the postharvest storage, the addition of silicon to the holding solution in the vase was able to significantly extend vase life, delay fresh weight decrease, and improve vase quality, as characterized by the antioxidant enzyme activities and mechanical stem strength. Taken together, silicon application, regardless of the approach, was able to effectively prolong the vase life and enhance the quality of cut peony flowers.

Strawberry (Fragaria × ananassa Duch.) can be easily propagated with daughter plants or through crown division, which are developed from the axillary bud at the axils of leaves. This study was conducted to investigate the effects of different cytokinins, auxins, and their combinations on the axillary bud growth in strawberry. Four cytokinins (6-benzyladenine, kinetin, zeatin, and thidiazuron (TDZ)) and three auxins (indole-3-acetic acid, indole-3-butyric acid, and naphthaleneacetic acid) at a concentration of 50 mg·L−1 were sprayed on the leaves three times in 10-day intervals. The expression levels of cytokinin, auxin, and meristem-related genes in the crowns were also investigated. The results showed that TDZ was the most effective hormone for the axillary bud growth, and also promoted plant growth. However, chlorophyll, soluble sugar, and starch contents in the leaves were lower after TDZ. TDZ activated the cytokinin signal transduction pathway, while repressing the auxin synthesis genes. Several meristem-related transcription factors were upregulated, which might be essential for the growth of the axillary buds. These results suggested that TDZ can improve the cultivation of strawberry, while further research is needed to explain the effect on phytochemistry.

This research examined the effects of the supplementary or night-interrupting (NI) blue (B) light supplied at a low intensity on the flowering, gene expression, and morphogenesis of chrysanthemum, a qualitative short-day plant. White (W) light-emitting diodes (LEDs) were used to provide light with a photosynthetic photon flux density (PPFD) of 180 μmol·m−2·s−1 during the photoperiod to grow the plants in a plant factory. The control group was constructed with plants that were exposed to a 10-h short day (SD10) treatment without any blue light. The B light in this research was used for 4 h to either (1) extend the photoperiod for plants at the end of a 9-h short day (SD) treatment as the sole light source (SD9 + 4B), (2) provide night interruption (NI) to plants in the 13-h long-day (LD) treatment (LD13 + NI − 4B), (3) provide NI to plants in the 10-h SD treatment (SD10 + NI − 4B), or (4) supplement the W LEDs at the end of a 13-h LD treatment (LD13 + 4B). Blue LEDs were used to provide the supplementary/NI light at 10 μmol·m−2·s−1 PPFD. The LD13 + NI − 4B treatment resulted in the greatest plant height, followed by LD13 + 4B. Plants in all treatments flowered. It is noteworthy that despite the fact that chrysanthemum is a qualitative SD plant, chrysanthemum plants flowered when grown in the LD13 + 4B and LD13 + NI − 4B treatments. Plants grown in the LD13 + 4B had the greatest number of flowers. Plants grown in the LD13 + 4B treatment had the highest expression levels of the cryptochrome 1, phytochrome A, and phytochrome B genes. The results of this study indicate that a 4-h supplementation of B light during the photoperiod increases flower bud formation and promotes flowering, and presents a possibility as an alternative method to using blackout curtains in LD seasons to practically induce flowering. The B light application methods to induce flowering in SD plants requires further research.

The beneficial effects that silicon (Si) has on plant growth as well as resistance to biotic and abiotic stresses have been well documented for many crops in recent years. However, few studies focus on the effects of Si on plant growth during the propagation stage of strawberry (Fragaria × ananassa, Duchesne). This study was conducted to investigate the optimal method for Si application during the cutting propagation of strawberry in soilless cultivation. Strawberry mother plants were supplied with Si through foliar spray, runner spray, or root drench before the cutting propagation, then half of the daughter plants in each treatment received continued Si supply through foliar spray or through root drench after the cutting propagation. The results showed that the plant height, petiole length and diameter, leaf length and width, shoot fresh and dry weights, and root fresh and dry weights were significantly increased by Si root drench both before and after the cutting propagation. Moreover, plants absorbed more Si by drench than by spray, and the absorbed Si was only able to be transported from the root to the shoot, and from the mother plant to the daughter plant. Further research found that the chlorophyll fluorescence parameter of the maximum quantum efficiency of the photosystem II (Fv/Fm) and the activities of superoxide dismutase, ascorbate peroxidase, and guaiacol peroxidase were also enhanced while catalase did not change under a high temperature stress in strawberry treated with Si before and after cutting propagation by root drench. Thus, Si application by drenching the roots during the whole propagation period is recommended to increase the quality of the strawberry daughter plants in soilless cultivation.

The effects of silicon (Si) on temperature stresses were investigated in poinsettia. Well-rooted cuttings supplemented with and without Si were exposed to 40 °C, and plants treated with or without Si during cutting propagation and cultivation were subjected to 4 °C. The results showed that almost all the stomata of cuttings without Si supplementation were closed, while some of them were still open in cuttings supplemented with Si under a high temperature stress. However, Si was not able to alleviate stomatal closure of poinsettia under low temperature stress. The increased epicuticular wax might contribute to enhanced resistance of poinsettia to low temperature stresses. In addition, poinsettia maintained a higher photosynthetic rate and lower malonaldehyde and hydrogen sulfide concentrations when supplemented with Si under high and low temperature stresses, which might contribute to lower APX activities. Overall, temperature stresses had negative impacts on the physiological characteristics of poinsettia, while Si could alleviate some effects of temperature stresses.

Carnation (Dianthus caryophyllus L.) is a major floricultural crop, cultivated widely for cut flowers. This study was conducted to determine the optimal supplementary light source for the cutting propagation of carnation ‘Dreambyul’ cuttings. Terminal cuttings were propagated in a glasshouse with an average of 260 µmol·m−2·s−1 photosynthetic photon flux density (PPFD) coming from the sun (the control), supplemented with one of three artificial light sources: mixed (red: blue: white = 6:1:1) light-emitting diodes (LED-mix), metal halide (MH) lamps, or high-pressure sodium (HPS) lamps. The supplementary light was provided from 7:00 to 17:00 h at 100 µmol·m−2·s−1 PPFD during propagation. The cuttings were kept on a fogged bench in a glasshouse for 25 days with 24/15 °C day/night temperatures and 88% relative humidity. Compared with the control, better root formation was observed from cuttings grown under the supplementary lights after 10 days. After 25 days of propagation, MH significantly increased the root length, root number, root fresh and dry weights, and shoot biomass, shoot length, and shoot fresh and dry weights. The best root ball formation and the highest root activities were also found in cuttings propagated with supplementary MH light. Supplementary light increased the plant temperature, quantum yield, stomatal conductance, and the contents of chlorophyll, soluble proteins, and carbohydrates. Overall, the root formation and development of carnation ‘Dreambyul’ cuttings were significantly promoted by the three supplementary light sources. Of the three, MH was identified as the optimal supplementary light source.

The objective of this study was to investigate the effect of light quality on the growth and contents of photosynthetic pigments and total flavonoids, the parameters of chlorophyll a fluorescence, antioxidant capacities, and enzyme activities. It was intended to preliminarily explore the internal mechanisms involved for the effect of light quality on the growth and physiology of Carpesium triste Maxim. Stem apex explants were cultured on the Murashige and Skoog (MS) medium under white (W), red (R), blue (B), or a 1:1 mixture of red and blue (RB) light-emitting diodes (LEDs) for four weeks. The RB induced sturdy plantlets and increased the contents of photosynthetic pigments and total flavonoids, photosynthetic electron transport and efficiency, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging capacity, and activities of antioxidant enzymes in the plantlets. Taken together, combinations of monochromatic red and blue LEDs could be used for the best production of high-quality C. triste plantlets in vitro.

Artificial light supplementation is widely used in modern agriculture. Due to their numerous advantages, light emitting diodes (LEDs) are widely used to effectively increase the yield or control the development of crops. In the present study, the effects of supplementary morning lighting (SML) with LEDs on the physiology and stomatal characteristics of strawberry plants were studied, with the aim of awakening the plant guard cells before sunrise and enabling strawberry plants to efficiently photosynthesize immediately after sunrise. Young daughter plants of ‘Maehyang’ and ‘Seolhyang’ strawberry cultivars that have just rooted were grown under LEDs with different wavelengths—white (W), red (R), mixed blue and red (BR, 1:1), and blue (B)—to investigate the effects of the SML on the physiology, stomatal characteristics, and growth. The SML was provided for 2 h at an intensity of 100 μmol·m−2·s−1 PPFD before sunrise every morning. A group without supplementary lighting was set as the control. The results showed that the different SML qualities have significantly affected the stomatal characteristics. The B SML promoted the stomatal opening more effectively compared to the other SMLs. The stomatal conductance and quantum yield (Fv/Fm) of leaves treated with the SMLs were higher than those of the control group. The B and BR SMLs most significantly affected the stomatal conductance and quantum yield (Fv/Fm). After 30 days of the SML treatments, it was observed that the B SML effectively improved the plant quality, chlorophyll content, and carbohydrate accumulation in the two strawberry cultivars. In general, a short-term exposure to blue light before sunrise can effectively improve the quality and promote the production of strawberry plants.

Runner propagation is an important process in strawberry cultivation, which influences plant survival and fruit yield during the commercial production. In South Korea, this process is carried out on plug tray benches that are set off the ground in greenhouses, rather than in open fields. During the propagation, the propagation media and fogging systems play an important role in the survival and rooting of daughter plants. The aim of this study is to investigate the influences of the different types of propagation media and various fogging treatments on the rooting and early growth of strawberry daughter plants. Two strawberry cultivars—‘Maehyang’ and ‘Seolhyang’—in a glasshouse, grown in four different propagation media-a peat moss-based mixture (PBM), rockwool cube (RWC), granular rockwool (GRW), and a coir-based mixture (CBM)—combined with five fogging durations, 0, 3, 6, 9 and 12 days were tested. PBM with 9–12 days of fogging was the most ideal combination for the rooting and early growth of daughter plants of the two strawberry cultivars, which increased the ratio of survival and rooting, number of new leaves, root length and maximised the fresh and dry weights of the aboveground and belowground runner biomass. However, fogging treatments shorter than 9 days led to a lower survival rate and rooting. RWC and GRW are not recommended for young plants of these two strawberry cultivars because their strong water-retentive properties could subject the root to water stress, which can lead to root rotting. The purpose of this study is to provide a reference for strawberry growers to improve the quality of plants and efficiency of production during the propagation period.

Silicon (Si) is a beneficial element for plants. To understand Si uptake and accumulation in poinsettia, the Si transporters and their expression patterns were investigated. Nodulin 26-like intrinsic membrane proteins (NIPs) act as transporters of water and small solutes, including silicic acid. In this study, one NIP member, designated EpLsi1, was identified. Additionally, a protein from the citrate transporter family, designated EpLsi2, was identified. Sequence analyses indicated that EpLsi1 belonged to the NIP-I subgroup, which has a low Si uptake capacity. Consistently, the measured tissue Si content in the poinsettia was less than 1.73 ± 0.17 mg·g−1 dry weight, which was very low when compared to that in high Si accumulators. The expressions of EpLsi1 and EpLsi2 in poinsettia cuttings treated with 0 mg·L−1 Si decreased under temperature stresses. A short-term Si supplementation decreased the expressions of both EpLsi1 and EpLsi2 in the roots and leaves, while a long-term Si supplementation increased the expression of EpLsi1 in the leaves, bracts, and cyathia, and increased the expression of EpLsi2 in the roots and leaves. Tissue Si content increased in the roots of cuttings treated with 75 mg·L−1 Si at both 4 and 40 °C, indicating that the transport activities of the EpLsi1 were enhanced under temperature stresses. A long-term Si supplementation increased the tissue Si content in the roots of poinsettia treated with 75 mg·L−1 Si. Overall, poinsettia was a low Si accumulator, the expressions of Si transporters were down-regulated, and the tissue Si content increased with temperature stresses and Si supplementation. These results may help the breeding and commercial production of poinsettia.

Insufficient exposure to light in the winter may result in a longer production periods and lower quality of seedlings in greenhouses for plug growers. Supplementary artificial lighting to plug seedlings may be one solution to this problem. The objective of this study was to assess the effects of the duration of the supplementary light on the growth and development of two watermelon cultivars, ‘Speed’ and ‘Sambok Honey’ grafted onto ‘RS-Dongjanggun’ bottle gourd rootstocks (Lagenaria siceraria Stanld). Seedlings were grown for 10 days in a glasshouse with an average daily natural light intensity of 340 μmol·m−2·s−1 photosynthetic photon flux density (PPFD) and daily supplementary lighting of 8, 12 or 16 h from mixed LEDs (W1R2B1, chip ratio of white:red:blue = 1:2:1) at a light intensity of 100 μmol·m−2·s−1 PPFD, a group without supplementary light was set as the control (CK). The culture environment in a glasshouse had 25/15 °C day/night temperatures, an 85 ± 5% relative humidity, and a natural photoperiod of 8 h. The results showed that all the growth and development parameters of seedlings grown with supplementary light were significantly greater than those without supplementary light (CK). The 12 and 16 h supplementary light resulted in greater growth and development parameters than the 8 h supplementary light did. The same trend was also found with the indexes that reflect the quality of the seedlings, such as the dry weight ratio of the shoot and root, total biomass, dry weight to height ratio of scions, and specific leaf weight. The 12 h and 16 h light supplements resulted in greater Dickson’s quality indexes compared to the 8 h supplementary light, and the 12 h supplementary light showed the greatest use efficiency of the supplementary light. 16 h of daily supplementary light significantly increased the H2O2 content and the antioxidant enzyme activities in seedlings compared to the other treatments. This indicated that 16 h of supplementary light led to certain stresses in watermelon seedlings. In conclusion, considering the energy consumption, 12 h of supplementary light was the most efficient in improving the quality of the two cultivars of grafted watermelon plug seedlings.

Browning is prevalent in tissue cultures of Paeonia lactiflora Pall. (herbaceous peony), and severely affects and restricts the growth and differentiation of the explants. In this study, dipping excised explants in a sodium chloride (NaCl) solution as a pretreatment, adding polyvinyl pyrrolidone (PVP) to the culture medium, storing planted explants at 4 °C for 24 h, and transferring planted explants to a new medium after 24 h were considered as browning-suppression methods in tissue cultures of herbaceous peony ‘Festival Maxima’. The treated petal explants were cultured in a culture room with a 16-hour photoperiod, 25 °C temperature, and 80% relative humidity in darkness for 4 to 8 weeks. The results demonstrated that dipping excised explants in a 0.5 g·L−1 NaCl solution, adding 0.5 g·L−1 PVP to the medium, storing planted explants at 4 °C for 24 h, and transferring planted explants to the same fresh medium after 24 h could effectively inhibit browning. Adding PVP to the medium led to the greatest browning suppression percentage of 95%. Storing planted explants at 4 °C for 24 h reduced the effectiveness of other treatments in suppressing browning. After 8 weeks, dipping excised explants in a NaCl solution resulted in the highest callus induction percentage of 75%, while storing explants at 4 °C for 24 h suppressed callus formation. It was observed in all treatments that decreases in browning was accompanied with higher levels of phenols and lower activities of phenylalanine ammonia-lyase (PAL) and polyphenoloxidase (PPO). Overall, the results suggest that dipping in a NaCl solution was effective in alleviating the browning issues of herbaceous peony tissue cultures, and had positive synergistic effects with PVP on browning suppression and callus induction.

Hydrogen sulfide (H2S) is endogenously produced in plant cells and plays an essential role in root development. Given its potential for future agricultural applications, the optimal concentration of sodium hydrosulfide (NaHS, an H2S donor) and the potential mechanisms for root development in the strawberry ‘Seolhyang’ were investigated in this study. The results showed that NaHS with a concentration of 1.250 mM had a positive effect on root development in strawberry. Further experiments showed that exogenous NaHS elevated the H2S content in the root. The dry root weight was increased by the 1.250 mM NaHS treatment, but was reduced by the hypotaurine (an H2S scavenger) treatment. Similar changes were found between H2S and soluble sugar contents, indicating that H2S enhanced the accumulation of soluble sugar. Therefore, it is suggested that the accumulation of soluble sugar induced by H2S is either directly or indirectly involved in root development in strawberry during plug production. Moreover, superoxide dismutase was shown to have contributed to the elevated H2O2 contents. These results contribute to our understanding of the role that H2S plays and some of the relevant mechanisms in which H2S regulates root development.

Astragalus membranaceus Bunge and Codonopsis lanceolata Benth. et Hook. f. are two medicinal species used to remedy inflammation, tumor, and obesity in Eastern medicine. Carbon dioxide (CO2) and supplemental lighting are two methods to enhance the growth, yield, and quality of crops. However, few studies have focused on the synergistic effects of CO2 and the supplemental light source on plug seedlings of medicinal species. In this study, uniform seedlings were grown with no supplemental light (the control) or under one of three supplemental light sources [high pressure sodium (HPS), metal halide (MH), or mixed light-emitting diodes (LEDs)] combined with one of three levels of CO2 (350, 700, or 1050 μmol·mol−1). The supplemental light (100 μmol·m−2·s−1 photosynthetic photon flux density) and CO2 were provided simultaneously from 10:00 pm to 2:00 am every day. The results showed that the supplemental lighting (LEDs, MH, and HPS) greatly improved the seedling quality with greater dry weights (of the shoot, root, and leaf), stem diameter, leaf area, and Dickson’s quality index (DQI) than those of the control in both species. An enriched CO2 at 1050 μmol·mol−1 accelerated the growth and development of plug seedlings, evidenced by the increased root and leaf dry weights, stem diameter, and DQI compared to the those from the other two CO2 enrichment levels. Moreover, LEDs combined with 1050 μmol·mol−1 CO2 not only increased the contents of soluble sugars but also the starch content. However, an enriched CO2 at 700 μmol·mol−1 was more suitable for the accumulation of total phenols and flavonoids. Furthermore, LEDs combined with 700 or 1050 μmol·mol−1 CO2 increased the chlorophyll, quantum yield, and stomatal conductance at daytime and nighttime for A. membranaceus and C. lanceolata, respectively. In conclusion, the data suggest that LEDs combined with CO2 at 1050 μmol·mol−1 is recommended for enhancing the growth and development of plug seedlings of A. membranaceus and C. lanceolata.

Astragalus membranaceus Bunge and Codonopsis lanceolata Benth. et Hook. f. are two famous medical species in Korea, China, and Japan, mainly used for treating diseases including cancer, obesity, and inflammation. Manipulation of the difference between the day and night temperatures (DIF) is an efficient horticultural practice to regulate the growth and development of vegetables in a glasshouse. However, little research has focused on how the DIF influences the plug seedling quality of medicinal plants. In this study, uniform plug seedlings were cultivated in three environmentally controlled chambers under an average daily temperature of 20 °C with negative (−10 °C), zero, or positive (+10 °C) DIFs, and the same relative humidity (75%), photoperiod (12 h), and light intensity (150 μmol·m−2·s−1 photosynthetic photon flux density with white LEDs). The results showed that the DIF had a noticeable effect on the growth, development, and morphology of A. membranaceus and C. lanceolata plug seedlings. The positive DIF (+10 °C) significantly increased the biomass (shoot, root, and leaf), stem diameter, and Dickson’s quality index, indicating an enhanced plug seedling quality. Moreover, the contents of primary and secondary metabolites, including soluble sugar, starch, total phenols and flavonoids, were higher with higher DIFs, where the maximum values were found at 0 °C or +10 °C DIF. Furthermore, the increases in the chlorophyll content and stomatal conductance were obtained in a positive DIF, indicating that a positive DIF was favorable to photosynthesis. An analysis of the gene expression showed that a positive DIF (+10 °C) up-regulated the expression of photosynthetic genes, including GBSS, RBCL, and FDX. In conclusion, the results of this study recommend a positive DIF (+10 °C) for enhancing the quality of A. membranaceus and C. lanceolata plug seedlings.

Astragalus membranaceus and Codonopsis lanceolata are two important medical herbs used in traditional Oriental medicine for preventing cancer, obesity, and inflammation. Night temperature is an important factor that influences the plug seedling quality. However, little research has focused on how the night temperature affects the growth and development of plug seedlings of these two medicinal species. In this study, uniform plug seedlings were cultivated in three environmentally controlled chambers for four weeks under three sets of day/night temperatures (25/10 °C, 25/15 °C, or 25/20 °C), the same relative humidity (75%), photoperiod (12 h), and light intensity (150 μmol·m−2·s−1 PPFD) provided by white LEDs. The results showed that night temperature had a marked influence on the growth and development of both species. The night temperature of 15 °C notably enhanced the quality of plug seedlings evidenced by the increased shoot, root, and leaf dry weights, stem diameter, and Dickson’s quality index. Moreover, a night temperature of 15 °C also stimulated and increased contents of primary and secondary metabolites, including soluble sugar, starch, total phenols and flavonoids. Furthermore, the 15 °C night temperature increased the chlorophyll content and stomatal conductance and decreased the hydrogen peroxide content. Analysis of the gene expression showed that granule-bound starch synthase (GBSS), ribulose bisphosphate carboxylase large chain (RBCL), and ferredoxin (FDX) were up-regulated when the night temperature was 15 °C. Taken together, the results suggested that 15 °C is the optimal night temperature for the growth and development of plug seedlings of A. membranaceus and C. lanceolata.

The effect of the exogenous hormone and light quality on breaking hypocotyl and epicotyl dormancy was studied. The results showed that the greatest percentage of hypocotyl dormancy breaking was observed with the Murashige and Skoog (MS) medium supplemented with or without 1.0 mg·L−1 gibberellin 3 (GA3), while ABA and endosperm greatly inhibited hypocotyl dormancy breaking. This suggests that hypocotyl dormancy of the Paeonia ostii ‘Fengdan’ embryo could be easily overcome by removing constraints of the surrounding endosperm, and ABA may be one of the constraint factors contained in the endosperm. The percentage of epicotyl dormancy breaking was also greatly affected by the concentration of 6-benzylaminopurine (BA) and GA3. Compared to BA by itself, adding GA3 to the medium containing BA highly enhanced epicotyl dormancy breaking, with the greatest percentage of epicotyl dormancy breaking in MS medium supplemented with both 0.5 mg·L−1 BA and 0.5−1.0 mg·L−1 GA3. The percentage of hypocotyl and epicotyl dormancy breaking was also affected by light and its quality. Red light-emitting diodes (LEDs) had the same effect as a dark condition on the hypocotyl dormancy breaking, while blue LEDs and a combination of red and blue LEDs had a negative effect on the hypocotyl dormancy breaking. Unexpectedly, blue LEDs greatly enhanced, whereas red LEDs inhibited, epicotyl dormancy breaking. Conclusively, a two-stage culture method was recommended for breaking the hypocotyl and epicotyl dormancy: hypocotyl dormancy was broken first using the MS medium without any plant growth regulators in the dark (25 °C), and epicotyl dormancy was subsequently broken with the MS medium supplemented with both 1.0 mg·L−1 GA3 and 0.5 mg·L−1 BA under blue light.