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When applied in the same concentration to tomato plants, cadmium sulfate (CdSO4) and zinc sulfate (ZnSO4) were transported from soil to roots and from roots to shoots more readily than their nano counterparts: cadmium sulfide quantum dots (CdS QD) and zinc sulfide quantum dots (ZnS QD). Compared to the CdS QD, he higher rate of transport of CdSO4 resulted in a greater negative effect on growth, chlorophyll content, antioxidant properties, lipid peroxidation and activation of antioxidant defence systems. Although ZnSO4 was transported more rapidly than ZnS QD, the overall effect of Zn addition was positive (increase in total plant mass, stem length, antioxidant content and decrease in lipid peroxidation). However, these effects were more pronounced in the case of ZnS QD, suggesting that the mechanisms underpinning the activity of ZnS QD and ZnSO4 were different. Thus, the risk of phytotoxicity and food chain transfer of the two elements depended on their form (salt or nanoform), and consequently their effects on plants' growth and physiology were different. This work elucidates the mechanisms underlying the responses of CdS QD and ZnS QD in contrast to those of their corresponding salts on tomato plants. Our results showed that faster transport from roots to leaves in the case of salts in respect to the nanoform augment their detrimental impact on tomato's antioxidant properties and growth and make the nanoform of both a better alternative for crop application either as fertilizers or as pesticides. [ABSTRACT FROM AUTHOR]

In order to elucidate the effects of low-temperature stress on the photosynthetic and stomatal properties of strawberry leaves during the flowering phase, the perennial strawberry cultivar 'Selva' was selected as the experimental material. The environmental control experiment was designed and conducted at Nanjing University of Information Science and Technology (NUIST) with Venlo greenhouse and artificial climate chamber in 2022. Two low temperature levels (15°C/5°C, 20°C /10°C) were set, and each of them represented day temperature with night temperature. Treatment T1 and T2 were used to distinguish them. The duration of low temperature was set at 3d, 6d, and 9d. The plants grown in the greenhouse with temperature set at 25°C/15°C were used as the control group (CK). Photosynthetic parameters and stomatal indices were determined for the leaves. The results showed that: (1) low temperature stress significantly inhibited the photosynthesis of strawberry, with the intensification of low temperature, the maximum net photosynthetic rate (Pnmax), light saturation point (LSP), stomatal conductivity (Gs), transpiration rate (Tr) gradually decreased, while light compensation point (LCP), dark respiration rate (Rd), intercellular CO2 concentration (Ci), stomatal limit (Ls) and water use efficiency (WUE) tended to increase. The main cause of the reduced photosynthetic rate was stomatal restriction. (2) Low temperature stress reduced the content of chlorophyll a, chlorophyll b, total chlorophyll content (a+b) and carotenoids in leaves. However, as the duration lengthened, the photosynthetic pigment content increased slightly, although it remained significantly lower than CK. (3) Low temperature stress had a particularly significant effect on leaf stomatal characteristics, i.e. the stomatal length, stomatal width, stomatal open degree, stomatal perimeter, stomatal area and stomatal opening ratio, which all decreased significantly with the decrease of temperature and the increase of the duration. Stomatal density tended to decrease but not significantly. This study showed that low temperatures reduced the stomatal size and the chlorophyll content, inhibiting the photosynthetic capacity of the leaves during the flowering stage. [ABSTRACT FROM AUTHOR]

Summary: Species of holopelagic Sargassum are responsible for Caribbean golden tides, commonly known as 'Sargassum events'. These events mainly comprise Sargassum fluitans and Sargassum natans I, which are exposed to high levels of irradiance, but also self‐shading within their floating masses. In this study, we grew S. fluitans and S. natans I and acclimated them to low‐light conditions at 23°C in the laboratory to explore their responses to increasing light intensities. Photosynthesis, respiration, growth, and pigment content were evaluated over 3 weeks. S. fluitans and S. natans I photoacclimate to higher irradiances by decreasing their chlorophyll a and c contents. An increase in maximum photosynthesis and respiration rates was observed under high light, although differences occurred in the saturation irradiance and the initial slope of the photosynthesis versus irradiance curve. These adjustments were reflected in S. fluitans daily growth (from 2% to 7% d−1 at low to high light, respectively) and tissue nitrogen content (1.6–2.7%) but were absent in S. natans I (~1% d−1). The photosynthetic physiology of S. fluitans under these conditions suggests lower light requirements without compromising growth; however, under high light a higher photosynthetic performance was observed. Combining physiological and growth studies in holopelagic Sargassum species will serve as a baseline to understand and explain the success and overgrowth of these species along the Caribbean coast. [ABSTRACT FROM AUTHOR]

We establish a general kinetic scheme for the energy transfer and radical-pair dynamics in photosystem I (PSI) of Chlamydomonas reinhardtii, Synechocystis PCC6803, Thermosynechococcus elongatus and Spirulina platensis grown under white-light conditions. With the help of simultaneous target analysis of transient-absorption data sets measured with two selective excitations, we resolved the spectral and kinetic properties of the different species present in PSI. WL-PSI can be described as a Bulk Chl a in equilibrium with a higher-energy Chl a, one or two Red Chl a and a reaction-center compartment (WL-RC). Three radical pairs (RPs) have been resolved with very similar properties in the four model organisms. The charge separation is virtually irreversible with a rate of ≈900 ns−1. The second rate, of RP1 → RP2, ranges from 70–90 ns−1 and the third rate, of RP2 → RP3, is ≈30 ns−1. Since RP1 and the Red Chl a are simultaneously present, resolving the RP1 properties is challenging. In Chlamydomonas reinhardtii, the excited WL-RC and Bulk Chl a compartments equilibrate with a lifetime of ≈0.28 ps, whereas the Red and the Bulk Chl a compartments equilibrate with a lifetime of ≈2.65 ps. We present a description of the thermodynamic properties of the model organisms at room temperature. [ABSTRACT FROM AUTHOR]

A two-year field experiment was conducted to measure the effects of densification methods on photosynthesis and yield of densely planted wheat. Inter-plant and inter-row distances were used to define ratefixed pattern (RR) and row-fixed pattern (RS) density treatments. Meanwhile, four nitrogen (N) rates (0, 144, 192, and 240 kg N ha-1, termed N0, N144, N192, and N240) were applied with three densities (225, 292.5, and 360 x 104 plants ha-1, termed D225, D292.5, and D360). The wheat canopy was clipped into three equal vertical layers (top, middle, and bottom layers), and their chlorophyll density (ChD) and photosynthetically active radiation interception (FIPAR) were measured. Results showed that the response of ChD and FIPAR to N rate, density, and pattern varied with different layers. N rate, density, and pattern had significant interaction effects on ChD. The maximum values of whole-canopy ChD in the two seasons appeared in N240 combined with D292.5 and D360 under RR, respectively. Across two growing seasons, FIPAR values of RR were higher than those of RS by 29.37% for the top layer and 5.68% for the middle layer, while lower than those of RS by 20.62% for the bottom layer on average. With a low N supply (N0), grain yield was not significantly affected by density for both patterns. At N240, increasing density significantly increased yield under RR, but D360 of RS significantly decreased yield by 3.72% and 9.00% versus D225 in two seasons, respectively. With an appropriate and sufficient N application, RR increased the yield of densely planted wheat more than RS. Additionally, the maximum yield in two seasons appeared in the combination of D360 with N144 or N192 rather than of D225 with N240 under both patterns, suggesting that dense planting combined with an appropriate N-reduction application is feasible to increase photosynthesis capacity and yield. [ABSTRACT FROM AUTHOR]

Duckweeds span 36 species of free-floating aquatic organisms with body sizes ranging from 2 mm to 10 mm, where each plant body plan is reduced to a largely leaf-like structure. As an emerging crop, their fast growth rates offer potential for cultivation in closed systems. We describe a novel UK collection derived from low light (dLL) or high light (dHL) habitats, profiled for growth, photosynthesis, and photoprotection (non-photochemical quenching, NPQ) responses. Twenty-three accessions of three Lemna species and one Spirodela polyrhiza were grown under relatively low light (LL: 100 μmol m–2 s–1) and high light (HL: 350 μmol m–2 s–1) intensities. We observed broad within- and between-species level variation in photosynthesis acclimation. Duckweeds grown under HL exhibited a lower growth rate, biomass, chlorophyll, and quantum yield of photosynthesis. In HL compared with LL, carotenoid de-epoxidation state and NPQ were higher, whilst PSII efficiency (φPSII) and Chl a : b ratios were unchanged. The dLL plants showed relatively stronger acclimation to HL compared with dHL plants, especially Lemna japonica accessions. These achieved faster growth in HL with concurrent higher carotenoid levels and NPQ, and less degradation of chlorophyll. We conclude that these data support local adaptation to the light environment in duckweed affecting acclimation in controlled conditions. [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum L.) is an important vegetable crop that grows easily under controlled conditions, such as in greenhouses and hydroponics. To overcome freshwater scarcity, researchers are searching for alternatives to groundwater sources such as desalinated water (saline water) for irrigation. High salinity in irrigation water alters physiological functions and crop development, thereby reducing the yield. Best management practices and the use of grafted tomato plants on salt-tolerant rootstocks can alleviate salinity stress. The present study was conducted to address the impact of salinity stress on leaf transpiration (Tr), stomatal conductance (gs), photosynthesis (Pn), leaf chlorophyll content, proline content, and yield of hydroponically cultivated tomato plants. Saline (NaCl) water was used for the preparation of nutrient solution with three salinity levels, electrical conductivity (EC, dS m−1) of 2.5 (control), 6.0, and 9.5. Three commercial tomato cultivars (Valouro-RZ, Ghandora-F1, and Feisty-Red) were used. Both self-rooted plants and plants grafted onto Maxifort rootstocks were transplanted onto a perlite substrate. The recorded data revealed that all studied cultivars were critically affected by higher salinity (≈ 9.5 dS m-1) compared to low (≈ 2.5 dS m-1) and medium (≈ 6.0 dS m-1) salinity levels. The Variations in Tr, Pn, gs, chlorophyll content of leaf, and yield between medium and high salinity trials were reported at 3%, 5%, 9%, 5%, and 7.1%, respectively, whereas no significant differences were observed between low and medium salinities. However, at medium salinity levels, grafted plants performed better in photosynthesis than non-grafted plants. This is due to the accumulation of leaf proline, which maintains osmotic regulation and photosynthetic activity by preventing cell damage at medium salinities. Hence, this study confirmed the use of saline water for growing tomatoes under hydroponic conditions up to an EC of 6.0 dS m-1 including the EC of nutrient fertilizers. [ABSTRACT FROM AUTHOR]

Mixotrophic protists combine photosynthesis and phagotrophy to obtain energy and nutrients. Because mixotrophs can act as either primary producers or consumers, they have a complex role in marine food webs and biogeochemical cycles. Many mixotrophs are also phenotypically plastic and can adjust their metabolic investments in response to resource availability. Thus, a single species's ecological role may vary with environmental conditions. Here, we quantified how light and food availability impacted the growth rates, energy acquisition rates, and metabolic investment strategies of eight strains of the mixotrophic chrysophyte, Ochromonas. All eight Ochromonas strains photoacclimated by decreasing chlorophyll content as light intensity increased. Some strains were obligate phototrophs that required light for growth, while other strains showed stronger metabolic responses to prey availability. When prey availability was high, all eight strains exhibited accelerated growth rates and decreased their investments in both photosynthesis and phagotrophy. Photosynthesis and phagotrophy generally produced additive benefits: In low‐prey environments, Ochromonas growth rates increased to maximum, light‐saturated rates with increasing light but increased further with the addition of abundant bacterial prey. The additive benefits observed between photosynthesis and phagotrophy in Ochromonas suggest that the two metabolic modes provide nonsubstitutable resources, which may explain why a tradeoff between phagotrophic and phototrophic investments emerged in some but not all strains. [ABSTRACT FROM AUTHOR]

A pilot study in the field was conducted within the study station of the Field Crops Department / College of Agricultural Engineering Sciences / “University of Baghdad during winter season of 2022-2023” .In order to find out the role of chlorophyll nutrient spraying on some growth traits of two varieties of bread wheat. Using RCBD design. The results showed a significant superiority of the V1 variety in all studied traits such as (Plant height measured in centimeters, number of tillers per square meter, and dry weight flowering100%, “the growth rate of the crop is g.m 2 .d -1, the hay yield in “ton .ha-1 biological yield ton. ha -1”, flag leaf area (cm² ), chlorophyll concentration (SPAD), dry weight flag leaf g., flag leaf' specific gravity (g.), spike length (cm) which amounted to (100.04 cm, 281.34 g .m 2 .d -1, 242 .06 g.m 2 .d -1, 5.96 ton. ha, 11.79 ton .ha, 32.68 cm, 48.73 SPAD, 0.131 g., 0.0039 g. and 12.13 cm). respectively . comparative V2 . chlorophyll nutrient concentrations showed that the level of Ch1 (1500) mg. L -1 represented a considerable improvement in most of which comprise the following attributes “plant height cm”, “number of tillers m 2”, dry weight at flowering 100% g.m², “crop growth rate g. m² .d-1, yield of straw ton. ha., The biological yield ton. ha., flag leaf area (cm), chlorophyll concentrations (SPAD) and spike length (cm) that reached (93.15 cm, 315.00 tillers m 2, 257.08 g.m 2, 1.904 g.m², 5.96 ton. ha., 12.85 ton. ha., 29.30 cm, and 12.07 cm) respectively, compared to the concentrations of Ch2 and Ch3. [ABSTRACT FROM AUTHOR]

To explore leaf anatomical structures and photosynthetic characteristics of Geodorum plant, the anatomical structure of leaves, daily variation of photosynthesis, light response curve, CO2 response curve, chlorophyll content and other indexes of the narrowly endangered Geodorum eulophioides and widely spread G. densiflorum and G. attenuatum were measured. The results were as follows:(1)Three species of Geodorum did not have spongy and fenestrated tissue differentiation in their chloroplasts, and stomata were distributed only in the lower epidermis. Compared with G. densiflorum and G. eulophioides, G. attenuatum had a greater leaf thickness and smaller stomatal density, exhibiting structural characteristics that were more adaptable to low light environments.(2)The daily changes of net photosynthetic rate(Pn)of three species of Geodorum showed a “bimodal” curve, and the photosynthetic “lunch break” was mainly caused by non-stomatal limitation. The daily mean values of Pn and water use efficiency(WUE)showed that G. attenuatum > G. densiflorum > G. eulophioides, which indicated that G. eulophioides had a weaker ability of accumulating photosynthesis products, and its adaptive capacity to the arid environment was probably poorer.(3)Three species of Geodorum were all shade plants. G. densiflorum had the smallest light compensation point(LCP)and the largest light saturation point(LSP), and had a wider range of adaptation to light intensity; G. attenuatum had a high maximum net photosynthetic rate(Pmax)and apparent quantum efficiency(AQY), and its photosynthetic capacity was stronger; G. eulophioides had the smallest Pmax and the potential maximum net photosynthetic rate(Amax), and its photosynthetic capacity and CO2 utilization capacity were weaker.(4)The chlorophyll a(Chl a), chlorophyll b(Chl b)and total chlorophyll(Chl)contents of G. densiflorum and G. attenuatum were significantly(P<0.05)higher than those of G. eulophioide.(5)There were significant(P<0.05)correlations between the leaf thickness, mesophyll thickness, chlorophyll content, and Pmax of three species of Geodorum. It was concluded that the photosynthetic capacity and adaptability of G. eulophioides were poorer compared with G. densiflorum and G. attenuatum, which might be greatly related to its endangerment; appropriate shading and increased CO2 concentration favored photosynthesis in three species of Geodorum. The results of this study provide a reference for the analysis of the endangered causes of G. eulophioides and the conservation of germplasm resources of three Geodorum species. [ABSTRACT FROM AUTHOR]

• Mistletoes are keystone species in resource-poor environments. • Viscum rotundifolium parasitizes the evergreen tree Boscia albitrunca in arid savannas. • We measured photosynthesis, chlorophyll contents and water potential of B. albitrunca and V. rotundifolium. • Non-host B. albitrunca trees attained greater photosynthetic, chlorophyll contents and water potential rates than host trees and the mistletoe. • Host trees suffer reduced access to water and lower carbon gain due to mistletoe infection. Mistletoes can have detrimental effects on host trees. Mistletoe-infected trees may suffer from reduced growth and loss of vigor thereby contributing to low productivity of host trees. However, hosts may tolerate low levels of infection. This study aimed to determine photosynthetic rate, chlorophyll content and transpiration rate of a mistletoe-host pair (Viscum rotundifolium - Boscia albitrunca) and the water potential of two mistletoe host pairs (V. rotundifolium - B. albitrunca and Tapinanthus oleifolius-Senegalia mellifera) in a semi-arid savanna at Windhoek, Namibia. Photosynthetic rates were measured using a LI-6400XT photosynthesis system, while photosynthetic pigments were extracted in acetone and quantified spectrophotometrically. Plant water potential was measured using a Scholander pressure chamber. Results revealed greater photosynthetic rates and amounts of photosynthetic pigments in B. albitrunca than in V. rotundifolium while transpiration rates showed opposite trends to photosynthetic rates. Non-host B. albitrunca trees recorded significantly higher photosynthetic rates than the hosts, which suggests a parasite-induced reduction of photosynthetic rate in host plants. Water potential was greater in host trees than in mistletoes. These findings show negative effects of mistletoes on host trees, which may ultimately affect their reproduction and survival. Further research may be required to determine effects of parasite density on host trees. [ABSTRACT FROM AUTHOR]

Carbon dioxide is present in the Earth's atmosphere and it acts as a major contributor in greenhouse gases. Exposure to carbon dioxide can have devastating effects on a person's health. Green Biotechnology may contribute to the reduction of greenhouse gas emissions, in which plants play an important role as carbon sinks by sequestrating carbon through photosynthesis. Carbon sequestration refers to the long-term storage of carbon in plants, soils, geologic formations, and the ocean. Current work is focused on exploring carbon dioxide uptake by different methods of green biotechnology and how environmental pollution affects that uptake. The study examined how the relationship between environmental pollution and carbon sequestration can be optimized by the technique of green biotechnology which affects the overall plant health. For this purpose, leaves from twenty-six plant species including Michelia, Anona Squamosa, Catharantha roseus, Elaeis Guineenis, Hibiscus rosa sinensis, and Epipremnun pinnatum were taken and divided into two sets. One set was washed with water and the other one was left with dirt on it to demonstrate the effect of pollution on carbon sequestration. Leaves were placed in a transparent photosynthetic chamber equipped with CO2 and O2, and light biosensors. Chlorophyll concentration was determined using a spectrophotometer. Out of twenty-six different species of plants, Hibiscus rosa sinensis sequestered the least amount of CO2 among all the plants with 42 ppm while Anona Squamosa exhibited highest levels of CO2 sequestration with 1025 ppm. There is a correlation between carbon sequestration and chlorophyll content. Plants that show a substantial amount of carbon sequestrated also have a greater amount of chlorophyll that help in photosynthesis. Furthermore, it was found that the unpolluted leaves of Michelia removed 388 ppm CO2 from the environment while the polluted leaves removed only 145 ppm CO2. [ABSTRACT FROM AUTHOR]

Zinc-oxide nanoparticles (ZnO-NP) effect on crop physiology and zinc recovery remains poorly studied for acidic-sandy soils. To address this, greenhouse pot (plastic-pots, 6 kg soil, maize) experiments with ZnO-NP (50, 100, 150, 200 mg kg−1) applied via different methods (soil-drench, seed-coating and foliar-spray) was conducted in a 60 days study. Results revealed that ZnO-NP via seed-coating (100 mg kg−1) and soil-drench (150 mg kg−1) enhanced shoot and total P uptake, while ZnO-NPs (foliar) (50 mg kg−1) enhanced maize growth (6–11%), with agronomic and physiological improvements ultimately resulted in greater biomass (16–20%), Zn agronomic efficiency and uptake. Compared to ZnSO4 treatment and the control, seed-coating with 100 mg kg−1 ZnO-NP increased leaf chlorophyll and pigment content by 12–127%. Principal component analysis revealed a close association among growth traits, plant pigments, fluorescence parameters, total Zn and P concentration, and uptake with total biomass as influenced by ZnO-NPs. Thus, compared to conventional ZnSO4 and higher dosages of ZnO-NPs, foliar-spray of ZnO-NP at 50 mg kg−1, seed-coating at 100 mg kg−1, or soil-drench at 150 mg kg−1 increased maize biochemical characteristics, growth, biomass, and Zn agronomic efficiency. These elucidate important implications of ZnO-NP application for increasing plant development and Zn biofortification in acidic-sandy soils. [ABSTRACT FROM AUTHOR]

Abstract—The association of degradation of membrane-bound chlorophyll with changes in the dark respiration rates and photosynthesis in Festuca arundinacea Schreb. leaves under the influence of various concentrations of limited and aromatic hydrocarbons present in technogenic emissions was studied. One day after intoxication, a negative correlation between the content of non-phytol forms of pigments and the rate of photosynthesis was found. A positive correlation was found between the content of (1) phytol forms and the rate of photosynthesis and (2) non-phytol forms and the respiration rate. The relationships between the processes changed three days after characterizing the detoxifying and adaptive abilities of plants. [ABSTRACT FROM AUTHOR]

This study was conducted to examine the impacts of dust on leaf mineral elements and selected physiological responses of three different Oak species in Western Zagros, Iran. Three-year-old seedlings of the Oak species Quercus brantii, Q. libani and Q. infectoria were exposed to dust under natural conditions. Photosynthesis, chlorophyll, proline and selected leaf mineral elements were examined in a two-factorial experiment including species (Q. brantii, Q. libani and Q. infectoria) and dust exposure (dust-exposed and without dust as control). The results showed that dust had a significant effect on photosynthesis rate of all species. Dust decreased photosynthesis rate to about 38%, 13% and 32% for Q. brantii, Q. libani and Q. infectoria, respectively. Dust also had a significant effect on proline and chlorophyll content of Oak leaves. Q. infectoria had the lowest total chlorophyll content with 42%. Among the studied species, Q. libani appears to be most suitable for growing under dust exposure, as this species had the lowest reduction in chlorophyll and photosynthesis. Planting Q. libani on northern slopes in Zagros forests, where Oak forests receive higher precipitation, presumably enhances the success of forest restoration under the combined effects of climate change and dust exposure. [ABSTRACT FROM AUTHOR]

Rising temperatures and extreme heat events threaten rice production. Half of the global population relies on rice for basic nutrition, and therefore developing heat-tolerant rice is essential. During vegetative development, reduced photosynthetic rates can limit growth and the capacity to store soluble carbohydrates. The photosystem II (PSII) complex is a particularly heat-labile component of photosynthesis. We have developed a high-throughput chlorophyll fluorescence-based screen for photosynthetic heat tolerance capable of screening hundreds of plants daily. Through measuring the response of maximum PSII efficiency to increasing temperature, this platform generates data for modelling the PSII–temperature relationship in large populations in a small amount of time. Coefficients from these models (photosynthetic heat tolerance traits) demonstrated high heritabilities across African (Oryza glaberrima) and Asian (Oryza sativa , Bengal Assam Aus Panel) rice diversity sets, highlighting valuable genetic variation accessible for breeding. Genome-wide association studies were performed across both species for these traits, representing the first documented attempt to characterize the genetic basis of photosynthetic heat tolerance in any species to date. A total of 133 candidate genes were highlighted. These were significantly enriched with genes whose predicted roles suggested influence on PSII activity and the response to stress. We discuss the most promising candidates for improving photosynthetic heat tolerance in rice. [ABSTRACT FROM AUTHOR]

The connection between soil nitrogen availability, leaf nitrogen, and photosynthetic capacity is not perfectly understood. Because these three components tend to be positively related over large spatial scales, some posit that soil nitrogen positively drives leaf nitrogen, which positively drives photosynthetic capacity. Alternatively, others posit that photosynthetic capacity is primarily driven by above-ground conditions. Here, we examined the physiological responses of a non-nitrogen-fixing plant (Gossypium hirsutum) and a nitrogen-fixing plant (Glycine max) in a fully factorial combination of light by soil nitrogen availability to help reconcile these competing hypotheses. Soil nitrogen stimulated leaf nitrogen in both species, but the relative proportion of leaf nitrogen used for photosynthetic processes was reduced under elevated soil nitrogen in all light availability treatments due to greater increases in leaf nitrogen content than chlorophyll and leaf biochemical process rates. Leaf nitrogen content and biochemical process rates in G. hirsutum were more responsive to changes in soil nitrogen than those in G. max , probably due to strong G. max investments in root nodulation under low soil nitrogen. Nonetheless, whole-plant growth was significantly enhanced by increased soil nitrogen in both species. Light availability consistently increased relative leaf nitrogen allocation to leaf photosynthesis and whole-plant growth, a pattern that was similar between species. These results suggest that the leaf nitrogen–photosynthesis relationship varies under different soil nitrogen levels and that these species preferentially allocated more nitrogen to plant growth and non-photosynthetic leaf processes, rather than photosynthesis, as soil nitrogen increased. [ABSTRACT FROM AUTHOR]

In this study, we assessed the relationship between tubers quality of three varieties (INIAP Libertad, INIAP Josefina and Diacol Capiro) of Ecuador highland early of potato and two formulations of edaphic fertilizer sources. Leaf chlorophyll content (LCC) was evaluated with Chlorophyll Meter SPAD-502Plus. Samples were taken at different heights in three phenological stages: vegetative grow, flowering-formation of tubers and ripening-thickening. Several responses were found in the three potato varieties. Correlation between SPAD value and weight of tubers (W), dry matter (DM), specific gravity (SG) and good chips (GC) were significantly correlated with potato leaves chlorophyll content. For Libertad variety and formulation (KNO3 + NH4H2PO4 + KCl), at vegetative grow in upper strata of plant, the optimal mathematic function for SPAD value andW, DM, SG and GC were: y = 0.262x9.460 (R2 = 0.9938), y = 42.948 e0;01x (R2 = 0.5240), y = 100;13x0;05 (R2 = 0.3277) and y = 100;36x1;41 (R2 = 0.8681); at plant flowering-formation of tuber stage, the optimal function models were: y = 10;57 x1;06 (R2 = 0.8553), y = 28.789 e0;0024 (R2 = 0.9103), y = 100;07 x0;02 (R2 = 0.7543) and y = 0.468x + 64.361 (R2 = 0.9935); at plant ripening-thickening, the optimal function models were: y = 0.664 e0;02x (R2 = 0.7924), y = 29.370 e0;003x (R2 = 0.9572), y = 100;07 x0;02 (R2 = 0.8247) and y = 0.576x + 62.675 (R2 = 0.9690), respectively. Our results showed that the use of SPAD-520PLUS proved to be a rapid method for the determination of LCC, being an effective tool for estimating potato tuber quality. [ABSTRACT FROM AUTHOR]

Summary: In natural ecosystems, plants compete for space, nutrients and light. The optically dense canopies limit the penetration of photosynthetically active radiation and light often becomes a growth‐limiting factor for the understory. The reduced availability of photons in the lower leaf layers is also a major constraint for yield potential in canopies of crop monocultures. Traditionally, crop breeding has selected traits related to plant architecture and nutrient assimilation rather than light use efficiency. Leaf optical density is primarily determined by tissue morphology and by the foliar concentration of photosynthetic pigments (chlorophylls and carotenoids). Most pigment molecules are bound to light‐harvesting antenna proteins in the chloroplast thylakoid membranes, where they serve photon capture and excitation energy transfer toward reaction centers of photosystems. Engineering the abundance and composition of antenna proteins has been suggested as a strategy to improve light distribution within canopies and reduce the gap between theoretical and field productivity. Since the assembly of the photosynthetic antennas relies on several coordinated biological processes, many genetic targets are available for modulating cellular chlorophyll levels. In this review, we outline the rationale behind the advantages of developing pale green phenotypes and describe possible approaches toward engineering light‐harvesting systems. [ABSTRACT FROM AUTHOR]

Using the fluorescent method in the modification of Krasnoyarsk State University, we studied the development (as chlorophyll content, ∑CHL) and photosynthetic activity of phytoplankton in seven large flat reservoirs of the Volga River cascade (Russia) in August 2015–2017. In the period of the maximal warming of water, average ∑CHL varied in limits of 19.4–33.7 μg L−1 in the Upper Volga, 8.5–27.8 μg L−1 in the Middle Volga, and 5.2–11.3 μg L−1 in the Lower Volga. The photosynthetic activity coefficient (PhAC) varied mostly in limits of 0.12–0.59, with an average of 0.22–0.38 and only in 2017 decreased to minimal < 0.10 and average < 0.20. The average PhAC values show the normal physiological state of the phytoplankton of the Upper Volga during all periods of observation, with an occasional decrease in PhAC in the Middle Volga and low photosynthetic activity in the Lower Volga. A decrease in the average ∑Chl and PhAC in 2017 was under cyclonic windy weather with a large amount of precipitation, low solar radiation, and large volume of flow. A trend towards a decrease in ∑CHL, like a decrease in PhAC from the Upper Volga to the Lower Volga, is explained by an increase in the flow rate and volume of runoff downstream of the Volga River. [ABSTRACT FROM AUTHOR]

Solar-induced chlorophyll fluorescence, or SIF, is a part of the natural process of photosynthesis. SIF can be measured from space by instruments such as the Orbiting Carbon Observatory-2 (OCO-2), making it a useful proxy for monitoring gross primary production (GPP), which is a critical component of Earth's carbon cycle. The complex physical relationship between SIF and GPP is frequently studied using OCO-2 observations of SIF since they offer the finest spatial resolution available. However, measurement error (noise) and large gaps in spatial coverage limit the use of OCO-2 SIF to highly aggregated scales. To study the relationship between SIF and GPP across varying spatial scales, de-noised and gap-filled (i.e., Level 3) SIF data products are needed. Using a geostatistical methodology called cokriging, which includes kriging as a special case, we develop coSIF: a Level 3 SIF data product at a 0.05-degree resolution. As a natural secondary variable for cokriging, OCO-2 observes column-averaged atmospheric carbon dioxide concentrations (XCO 2 ) simultaneously with SIF. There is a suggested lagged spatio-temporal dependence between SIF and XCO 2 , which we characterize through spatial covariance and cross-covariance functions. Our approach is highly parallelizable and accounts for non-stationary measurement errors in the observations. Importantly, each datum in the resulting coSIF data product is accompanied by a measure of uncertainty. Extant approaches do not provide formal uncertainty quantification, nor do they leverage the cross-dependence with XCO 2 . [ABSTRACT FROM AUTHOR]

During low rainfall periods, rice plants often face drought stress, which would significantly affect rice yield. One of the methods to mitigate the problem is incorporating rice plants with fungi such as Trichoderma. This study evaluated the effects of encapsulated Trichoderma asperellum (UPM 40) on the growth and yield of rice plants planted in saturated and flooded soil conditions in response to drought stress. A randomized complete block factorial design was implemented with four replications and two factors. The first factor was encapsulated T. asperellum (UPM 40) concentration of 0 and 5 g. The second factor was the soil condition: saturated and flooded soil. The drought stress was imposed by halting watering during early anthesis for 14 days and resumed afterward. One of the significant interaction effects detected was on the relative water content of rice plants planted in flooded soil conditions and treated with T. asperellum (UPM 40), where the value was 78.51%, higher than the control of 72.09%, which showed the ability of the fungus to help rice plants alleviate detrimental effects of drought stress and delay the onset of adverse effects of drought stress. Thus, it contributed to the crop’s simultaneous improvement in rice yield compared to untreated plants in saturated soil. Applying 5 g encapsulated T. asperellum (UPM 40) to the rice plants would perform best in flooded soil conditions during drought stress. [ABSTRACT FROM AUTHOR]

Maize kernel growth is sensitive to heat stress, which is predicted to result in yield loss. However, the response of maize to short-term heat stress during different kernel-growth stages is still not clear. A 3-year field experiment, included two heat-stress treatments (LSH, lag-stage heat stress; FSH, effective-filling-stage heat stress), was conducted in 2019–2021. The results showed that LSH and FSH significantly reduced the grain yield by 8.7–14.9% and 11.6–17.6%, respectively, compared with the control (CK). LSH mainly reduced the kernel number per ear, and FSH mainly reduced the kernel weight. Heat stress reduced the SPAD and chlorophyll content during the effective-filling stage, but not in the lag stage. Photosynthesis was obviously reduced under heat stress during both stages; however, the photosynthesis rate during the lag stage was higher than during the effective-filling stage. The decreased amplitude of dry matter under LSH was higher than under FSH during the heating period. However, there was no difference between the CK and LSH samples in terms of dry-matter accumulation from the end of heat stress to harvest, which was significantly reduced under FSH. Additionally, decreased starch-synthesis-related enzyme activity, i.e., adenosine diphos-phoglucose pyrophosphprylase, contributed to the kernel number and kernel weight loss in LSH and FSH, respectively. The kernel-growth rate (per ear) was lowered, but the growth duration was not shortened in this study. Consequently, LSH mainly reduced the photosynthesis rate (Pn), resulting in kernel abortion and yield penalty. FSH mainly reduced the Pn and chlorophyll content, which reduced the kernel weight, and increased yield loss. [ABSTRACT FROM AUTHOR]

Oilseed crops require several micronutrients to support their physiological functions and reproductive phases. A deficiency of these nutrients can significantly reduce the yield and oil quality of oilseed crops. Soil application of micronutrients can reduce their deficiency and improve plant growth, yield, and oil quality. Oilseed rape (Brassica napus L.) is an important oilseed crop that produces oil with low levels of saturated fat and high levels of beneficial omega-3 fatty acids, which renders it a widely used cooking oil. However, the yield and oil quality of oilseed rape are significantly affected by the deficiency of boron (B) and zinc (Zn). This two-year field study determined the influence of sole and combined soil application of B and Zn on the physiological attributes of plants, seed and oil yields, and oil quality under semiarid climatic conditions. Nine different B and Z combinations, i.e., B0 + Zn0 (control), B0 + Zn8, B0 + Zn10, B1 + Zn0, B1 + Zn8, B1 + Zn10, B2 + Zn0, B2 + Zn8, and B2 + Zn10 (kg ha−1), were included in the study. Sole and combined application of B and Zn significantly altered physiological attributes, seed and oil yields, and oil quality. The highest values for plant height, number of siliques per plant, number of seeds per silique, 1000-seed weight, seed and oil yields, oil quality (higher stearic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, and lower erucic acid), and physiological traits (protein concentration, soluble sugar concentration, chlorophyll concentration, photosynthesis and transpiration rates, and stomatal conductance) were recorded with the combined application of 2 + 8 kg ha−1 B and Zn, respectively, during both years of this study. The lowest values of yield- and oil-quality-related traits and physiological attributes were recorded for the control treatment. A dose-dependent improvement was recorded in B and Zn contents in leaves, and the highest values were recorded with the combined soil application of 2 + 10 kg ha−1 B + Zn, respectively. It can be concluded that 2 + 8 kg ha−1 B + Zn should be applied to oilseed rape for higher seed and oil yields and better oil quality under semiarid climatic conditions. [ABSTRACT FROM AUTHOR]

The dynamics of the main photosynthetic structures are studied by mathematical modeling methods in this work. Chlorophyll portion variability in phytoplankton and formation of energy-intensive substances in the process of photosynthesis underlie the models. These cellular components are considered in terms of their participation in the growth of specific biomass. Computational experiments are conducted to simulate various degrees of environmental friendliness. The corresponding functions are built in accordance with seasonal fluctuations throughout the year in the Far East region of Russia. The stability of model solutions in long-term dynamics is also investigated. The models are tested for biological adequacy, and their effectiveness is compared. For the model selected as a result of the comparison, the optimal control problem was formulated and solved. This way reduces the space of the initial components of the model system. The main conclusion is that a step-by-step description of photosynthetic transformations gives a result close to the experimental description of phytoplankton production dynamics. [ABSTRACT FROM AUTHOR]

Cyclocarya paliurus has been traditionally used as a functional food in China. A hydroponic experiment was conducted to determine the effects of N and P additions on photosynthesis and chlorophyll fluorescence (ChlF) of C. paliurus seedlings. N and P additions significantly altered photosynthesis and ChlF in the seedlings, but responses of these parameters to the N and P concentrations varied at different developmental stages. The greatest net photosynthetic rate (PN) and actual photochemical efficiency of PSII (ФPSII) occurred in the treatment of 150.0 mg(N) L-1 and 25.0 mg(P) L-1 addition, whereas the highest maximum quantum yield of PSII (Fv/Fm) and water-use efficiency (WUE) were recorded with 150.0 mg(N) L-1 and 15.0 mg(P) L-1 on the 60th day after treatment. Significantly positive correlations of PN with leaf relative chlorophyll content, transpiration rate, WUE, Fv/Fm, and FPSII, as well as the ФPSII with the Fv/Fm, were found. Our results indicated that an optimal addition of N and P nutrients depends on their coupling effects on the photosynthetic capacity and PSII photochemistry. [ABSTRACT FROM AUTHOR]

To elucidate the adaptive strategies of Glechoma longituba in response to different light-quality colored films, the growth, photosynthesis, chloroplast ultrastructure, and triterpene acid accumulation were analyzed. In this study, four colored films improved electron transport and maintained the function of PSII, and allocated more light energy absorbed for photochemical reactions, thus increasing the photosynthetic capacity and ultimately improving dry mass accumulation. Additionally, blue film (BF) and green film (GF) enhanced photosynthesis by increasing stomatal openness and chlorophyll contents and maintaining chloroplast structural integrity, thereby promoting dry mass and triterpene acid (TA) accumulation of G. longituba. Red film excessively increased starch grains, inhibited photosynthate output and consequently reduced the concentration and yield of ursolic acid (UA). Yellow film decreased stomatal openness and chlorophyll concentrations, which was not conducive to chloroplast development, and also decreased the concentration and yield of UA. In conclusion, the application of BF and GF may represent an effective cultivation practice that can be used to achieve the highest TA yields in plantings of G. longituba. [ABSTRACT FROM AUTHOR]

Rice is not only an important staple food source for half of the world′s population, but also an excellent plant model for plant research. As an important part of the rice life cycle, rice seedling development stage is a process that combines multiple genetic, physiological, metabolic and signaling pathways. Since the rice seedling stage is susceptible to internal and external stimuli, the mechanism of various stimuli in the rice seedling growth stage has received extensive attentions. The photosynthesis of rice is affected by internal physiological and biochemical pathways, and external environmental factors. The content of chlorophyll can be used as an indicator of plant photosynthesis ability and developmental stage, which is one of the important indicators for monitoring plant growth and health. This study measured the chlorophyll content of different stages of rice seedlings and made a proteomics analysis. Taking rice seedlings of three stages as the research objects, the leaves of rice seedlings at three stages were collected in turn, and the content of their chlorophyll was determined. The first stage of the rice seedlings was normally growing up until 14 days, the second stage was continue growing up until suffered 7 days cold treatment (15 ℃), and the third stage was growing up 7 days at normal temperature after cold treatment. In this study, combined with statistical analysis methods such as principal component analysis and partial least squares discriminant analysis, and the differential proteomic analysis combined with statistical analysis methods were used to study the correlation between the differential expressed proteins and the changes of chlorophyll content. The results showed that seven metabolic pathways of starch and sucrose metabolism, glycolysis pathway, pentose phosphate pathway, photosynthesis and its carbon fixation, tricarboxylic acid cycle were enriched. Nearly 30 types of enzymes with strongly related to chlorophyll content were screened out, such as P42862, A0A0D3GZA9, Q8S5M6, A0A0E0HGC6 and so on. This study explored the metabolic pathways related with the changes of chlorophyll content, and proved that chlorophyll content can be used as an important indicator of plant growth and health from the perspective of proteomics. The relationship between chlorophyll content and the metabolic pathways, as well as the relationship between chlorophyll content and plant growth and health were explored, and an empirical model of certain reliability and universality was obtained. [ABSTRACT FROM AUTHOR]

The physiological state of overwintering tea leaves is crucial for the growth and quality formation of spring tea shoots. Low temperatures in winter can easily cause damage to overwintering tea plants, leading to leaf chlorosis and abnormal physiological functions. Many pieces of research have shown that shading could promote chlorophyll (Chl) accumulation in tea leaves, but the impact on overwintering tea plants is not yet known. In this study, different shading rates (no-shading, S0%; 30% shading, S30%; 75% shading, S75%) were used to treat overwintering tea plants, which explored the effect of shading on the color and physiological functions of tea leaves. The results showed that Chl, carotenoid, and soluble sugar (SS) contents were S75% > S30% > S0%, and the net photosynthetic rate (Pn) was S75% > S30% > S0%. Transcriptome analysis showed that the genes involved in chlorophyll and carotenoid metabolism (such as protochlorophyllide reductase POR and zeaxanthin epoxidase ZEP) and photosynthesis (such as photosystem II P680 reaction center D2 protein PsbA and photosystem II CP47 chlorophyll apoprotein PsbB) were significantly up-regulated under shading. In addition, many differentially expressed genes (DEGs) were enriched in "starch and sucrose metabolism (ko00500)" and "anthocyanin biosynthesis (ko00942)" pathways. In summary, this study provided a theoretical basis and technical support for maintaining green leaves and normal physiological functions of overwintering tea plants. [ABSTRACT FROM AUTHOR]

L-myo-inositol phosphate synthase (MIPS; EC 5.5.1.4) encodes the enzyme synthesizing Myo-inositol for plant growth and development. Myo-inositol and its phosphate derivatives are involved in various physiological functions ranging from cell wall synthesis, chromatin remodeling, signal transduction, and providing stress responses. In the present study, we report that MIPS regulates chlorophyll content and photosynthesis efficiency via the ethylene signaling pathway. We have used Triticum aestivum MIPS-A (TAMIPS-A) for the present study and characterized it by mutant complementation and overexpression studies in Arabidopsis. TaMIPS-A overexpressing Arabidopsis transgenics were analyzed physiologically under thermal stress conditions. Analysis of overexpression TaMIPS-A transgenics under control and thermal stress conditions revealed them to have enhanced photosynthetic potential under heat stress. When TaMIPS-A overexpression (OE) Arabidopsis transgenics are supplemented with either ACC, the ethylene precursor, or AgNO3, the ethylene signaling inhibitor indicated that MIPS regulates the photosynthetic efficiency and chlorophyll content via the ethylene signaling pathway under control and thermal stress. Expression analysis of essential genes involved in the ethylene biosynthetic and signaling pathway corroborated. [ABSTRACT FROM AUTHOR]

Redox regulation of plastid gene expression and different metabolic pathways promotes many activities of redox-sensitive proteins. We address the question of how the plastid redox state and the contributing reducing enzymes control the enzymes of tetrapyrrole biosynthesis (TBS). In higher plants, this metabolic pathway serves to produce chlorophyll and heme, among other essential end products. Because of the strictly light-dependent synthesis of chlorophyll, tight control of TBS requires a diurnal balanced supply of the precursor 5-aminolevulinic acid (ALA) to prevent the accumulation of photoreactive metabolic intermediates in darkness. We report on some TBS enzymes that accumulate in a light intensity-dependent manner, and their contents decrease under oxidizing conditions of darkness, low light conditions, or in the absence of NADPH-dependent thioredoxin reductase (NTRC) and thioredoxin f1 (TRX-f1). Analysis of single and double trxf1 and ntrc mutants revealed a decreased content of the early TBS enzymes glutamyl-tRNA reductase (GluTR) and 5-aminolevulinic acid dehydratase (ALAD) instead of an exclusive decrease in enzyme activity. This effect was dependent on light conditions and strongly attenuated after transfer to high light intensities. Thus, it is suggested that a deficiency of plastid-localized thiol-redox transmitters leads to enhanced degradation of TBS enzymes rather than being directly caused by lower catalytic activity. The effects of the proteolytic activity of the Clp protease on TBS enzymes were studied by using Clp subunit-deficient mutants. The simultaneous lack of TRX and Clp activities in double mutants confirms the Clp-induced degradation of some TBS proteins in the absence of reductive activity of TRXs. In addition, we verified previous observations that decreased chlorophyll and heme levels in ntrc could be reverted to WT levels in the ntrc/Δ2cp triple mutant. The decreased synthesis of 5-aminolevulinic acid and porphobilinogen in ntrc was completely restored in ntrc/Δ2cp and correlated with WT-like levels of GluTR, ALAD, and other TBS proteins. [ABSTRACT FROM AUTHOR]

Impact of nitrogen (N) supply on photosynthesis and N, P, and K status of wheat, particularly ancient wheats lacks clarity. Hence, clarification of post-anthesis photosynthesis and N, P, and K status of ancient emmer compared to the improved durum and bread wheats was aimed at. Five field-grown ancient emmer, one improved durum and an improved bread wheat exposed to a wide range of N fertilizer (i.e. 0, 25, 50, and 75 kg ha−1 N) were tested in two consecutive years. Chlorophyll and carotenoids concentrations of the emmer and improved wheats were increased by 39–63% and 29–45%, respectively in response to N supply. Mesophyll conductance and net photosynthetic rate of the improved bread wheat were increased by 150% and 60%, respectively, with increase in N supply, but those of the emmer wheats were decreased in response to the medium (0–43%) and high N (0–37%) supplies. Emmer wheat out-numbered the improved wheats in terms of mesophyll conductance and net photosynthetic rate under the low N supply but the reverse was true with the high N supply. Leaf (1–2.2, 3.2–7.7, and 16.8–35 mg g−1, respectively) and grain (2.38–6.4, 5.6–12.1, and 20.5–28.9 mg g−1, respectively) P, leaf N, and grain K concentrations responded positively to the N supply and emmer wheats equaled or exceeded those of the improved wheats particularly when grown in the absence of high N supplies. The presented data indicates that ancient emmer wheats are potent to be employed to incorporate nutrient-acquiring traits into the modern wheats. [ABSTRACT FROM AUTHOR]

Light provides energy for photosynthesis and is also an important environmental signal that regulates plant growth and development. Ribose-5-phosphate isomerase plays a crucial role in photosynthesis. However, ribose-5-phosphate isomerase has yet to be studied in soybean photosynthesis. To understand the biological function of GmRPI2, in this study, GmRPI2 was cloned, plant overexpression vectors and gene editing vec‐ tors were successfully constructed, and transformed into recipient soybean JN74 using the Agrobacterium- mediated method. Using qRT-PCR, we analyzed that GmRPI2 gene expression was highest in leaves, second highest in roots, and lowest in stems. Promoter analysis revealed the presence of multiple cis-acting elements related to light response in the promoter region of GmRPI2. Compared with the control soybean plants, the net photosynthetic rate and transpiration rate of the overexpression lines were higher than those of the control and gene editing lines, while the intercellular CO2 concentration was significantly lower than that of the con‐ trol and gene editing lines; the total chlorophyll, chlorophyll a, chlorophyll b contents and soluble sugar con‐ tents of the overexpression plants were significantly higher than those of the recipient and editing plants, indicating that the GmRPI2 gene can increase The GmRPI2 gene can increase the photosynthetic capacity of soybean plants, providing a theoretical basis and genetic resources for improving soybean yield by regulating photosynthetic efficiency. [ABSTRACT FROM AUTHOR]

The first step of photosynthesis in plants is performed by the light-harvesting complexes (LHC), a large family of pigment-binding proteins embedded in the photosynthetic membranes. These complexes are conserved across species, suggesting that each has a distinct role. However, they display a high degree of sequence homology and their static structures are almost identical. What are then the structural features that determine their different properties? In this work, we compared the two best-characterized LHCs of plants: LHCII and CP29. Using molecular dynamics simulations, we could rationalize the difference between them in terms of pigment-binding properties. The data also show that while the loops between the helices are very flexible, the structure of the transmembrane regions remains very similar in the crystal and the membranes. However, the small structural differences significantly affect the excitonic coupling between some pigment pairs. Finally, we analyzed in detail the structure of the long N-terminus of CP29, showing that it is structurally stable and it remains on top of the membrane even in the absence of other proteins. Although the structural changes upon phosphorylation are minor, they can explain the differences in the absorption properties of the pigments observed experimentally. [ABSTRACT FROM AUTHOR]

Tomatoes are one of the most popular and widely grown vegetables in the world. Due to the excessive and unconscious use of chemical fertilizers used in tomato cultivation for high yields, economic and environmental problems such as loss of soil fertility and pollution can occur. So, in this study, Plant Growth Promoting Rhizobacteria (PGPR) bacteria were applied to the soil in a tuff carrier medium and the yield parameters of tomato plants were investigated. Bandita F1 tomato seedlings were used in this study. Approximately 108 cfu g−1 bacteria were added to the medium sized tuff material (8 × 8 × 11 mm). The tuff materials with PGPR were applied to the soil according to the experimental group. A trial model was created as the plots in which bacteria inoculated tuff material was applied and the plots without bacteria were applied. Approximately 50 g of Tuff + PGPR material was applied to each plant root and irrigated according to the water requirement of the plants. The highest yield (6016 kg da-1) was obtained when tuff inoculated with bacteria was applied. In this application, an increase of 9.0% was recorded compared to the control group. In the application of tuff inoculated with bacteria, the amount of chlorophyll increased by 4.66%, membrane permeability by 3.0% and the amount of photosynthesis by 3.91% compared to the control group. It was found that the use of tuff materials inoculated with bacteria would have a positive effect on the yield of the tomato plant. [ABSTRACT FROM AUTHOR]

Tobacco mosaic virus (TMV) is a systemic virus that poses a serious threat to crops worldwide. In the present study, a series of novel 1-phenyl-4-(1,3,4-thiadiazole-5-thioether)-1H-pyrazole-5-amine derivatives was designed and synthesized. In vivo antiviral bioassay results indicated that some of these compounds exhibited excellent protective activity against TMV. Among the compounds, E2 (EC50 = 203.5 μg/mL) was superior to the commercial agent ningnanmycin (EC50 = 261.4 μg/mL). Observation of tobacco leaves infected with TMV-GFP revealed that E2 could effectively inhibit the spread of TMV in the host. Further plant tissue morphological observation indicated that E2 could induce the tight arrangement and alignment of the spongy mesophyll and palisade cells while causing stomatal closure to form a defensive barrier to prevent viral infection in the leaves. In addition, the chlorophyll content of tobacco leaves was significantly increased after treatment with E2, and the net photosynthesis (Pn) value was also increased, which demonstrated that the active compound could improve the photosynthetic efficiency of TMV-infected tobacco leaves by maintaining stable chlorophyll content in the leaves, thereby protecting host plants from viral infection. The results of MDA and H2O2 content determination revealed that E2 could effectively reduce the content of peroxides in the infected plants, reducing the damage to the plants caused by oxidation. This work provides an important support for the research and development of antiviral agents in crop protection. [ABSTRACT FROM AUTHOR]

Background: Magnesium chelatase plays an important role in photosynthesis, but only a few subunits have been functionally characterized in cassava. Results: Herein, MeChlD was successfully cloned and characterized. MeChlD encodes a magnesium chelatase subunit D, which has ATPase and vWA conservative domains. MeChlD was highly expressed in the leaves. Subcellular localization suggested that MeChlD:GFP was a chloroplast-localized protein. Furthermore, the yeast two-hybrid system and BiFC analysis indicated that MeChlD interacts with MeChlM and MePrxQ, respectively. VIGS-induce silencing of MeChlD resulted in significantly decreased chlorophyll content and reduction the expression of photosynthesis-related nuclear genes. Furthermore, the storage root numbers, fresh weight and the total starch content in cassava storage roots of VIGS-MeChlD plants was significantly reduced. Conclusion: Taken together, MeChlD located at the chloroplast is not only required for chlorophyll biosynthesis and photosynthesis, but also affecting the starch accumulation in cassava. This study expands our understanding of the biological functions of ChlD proteins. [ABSTRACT FROM AUTHOR]

Ethephon was widely used in rubber tree plantation to stimulate latex production. Numerous studies demonstrated that ethephon treatment prolongs the flow of the latex and promotes latex regeneration in the trunk of mature rubber tree seedlings. However, how rubber tree leaves responded to ethephon treatment on the trunk is still unknown. We used rubber tree seedlings to detect the physiological response of leaves after the trunk treatment with ethephon. The photosynthetic rate, the sugar and starch content, as well as the enzyme activities involved in sugar metabolism were measured after 0, 12, 24, 36 and 48 hours with 0.6% ethephon treatment. The result demonstrated that ethephon treatment increased latex production on the trunk, while the net photosynthetic rate, transpiration rate, and stomatal conductance in leaves were significantly reduced. At the same time, sucrose decreased significantly with concomitant slight increase in glucose and fructose. Also, the enzymatic activities of Sucrose Phosphate Synthase (SPS), Sucrose Synthase (SS) and Neutral/alkaline Invertase (NI) increased significantly after ethephon treatment. Ethephon treatment affected the starch content, but did not change the composition of starch in rubber tree seedlings leaves; the overall starch changing pattern was similar to that of sucrose in leaves. It can be concluded that ethylene-stimulated latex production in rubber tree seedlings is partly due to the alteration of sucrose metabolism in leaves, and ethylene has an adverse physiological effect on rubber trees. [ABSTRACT FROM AUTHOR]

In autumn and spring, citrus leaves with a Ponkan (Citrus reticulata Blanco cv. Ponkan) genetic background (Harumi, Daya, etc.) are prone to abnormal physiological chlorosis. The effects of different degrees of chlorosis (normal, mild, moderate and severe) on photosynthesis and the chlorophyll metabolism of leaves of Citrus cultivar (Harumi) were studied via field experiment. Compared with severe chlorotic leaves, the results showed that chlorosis could break leaf metabolism balance, including reduced chlorophyll content, photosynthetic parameters, antioxidant enzyme activity and enzyme activity related to chlorophyll synthesis, increased catalase and decreased enzyme activity. In addition, the content of chlorophyll synthesis precursors showed an overall downward trend expected for uroporphyrinogen III. Furthermore, the relative expression of genes for chlorophyll synthesis (HEMA1, HEME2, HEMG1 and CHLH) was down-regulated to some extent and chlorophyll degradation (CAO, CLH, PPH, PAO and SGR) showed the opposite trend with increased chlorosis. Changes in degradation were more significant. In general, the chlorosis of Harumi leaves might be related to the blocked transformation of uroporphyrinogen III (Urogen III) to coproporphyrinogen III (Coprogen III), the weakening of antioxidant enzyme system activity, the weakening of chlorophyll synthesis and the enhancement in degradation. [ABSTRACT FROM AUTHOR]

Simple Summary: This study investigates the spatial analysis of morphological and chemical changes and how reflectance hyperspectroscopy and fluorescence kinetics spectroscopy can enhance our understanding of biophysical, biochemical, and photochemical changes in Codiaeum variegatum (L.) A. Juss, a plant with variegated leaves and different pigments. The analysis included pigment profiling, hyperspectral curves, chlorophyll a fluorescence induction kinetics, and multivariate analyses associated with 23 JIP test parameters and 34 vegetation indexes. The results show that the analysis of chemical composition combined with vegetation indexes, such as PRI, PSSRc, ARI1, RARS, and SIPI, are highly correlated with pigment concentration and photochemical components of photosystems in leaves. Furthermore, decreased damage to energy transfer in the electron transport chain is associated with the accumulation of carotenoids, anthocyanins, flavonoids, and phenolic compounds linked with specific wavelengths. Our results reveal the potential of optical spectroscopy techniques and multivariate data analyses to enhance the management and monitoring of the leaf color status of plants. This is the first study and report on the monitoring of nonuniform leaves, particularly in the alteration of photosystem changes in variegated leaves together with high-throughput analyses. The adjustments that occur during photosynthesis are correlated with morphological, biochemical, and photochemical changes during leaf development. Therefore, monitoring leaves, especially when pigment accumulation occurs, is crucial for monitoring organelles, cells, tissue, and whole-plant levels. However, accurately measuring these changes can be challenging. Thus, this study tests three hypotheses, whereby reflectance hyperspectroscopy and chlorophyll a fluorescence kinetics analyses can improve our understanding of the photosynthetic process in Codiaeum variegatum (L.) A. Juss, a plant with variegated leaves and different pigments. The analyses include morphological and pigment profiling, hyperspectral data, chlorophyll a fluorescence curves, and multivariate analyses using 23 JIP test parameters and 34 different vegetation indexes. The results show that photochemical reflectance index (PRI) is a useful vegetation index (VI) for monitoring biochemical and photochemical changes in leaves, as it strongly correlates with chlorophyll and nonphotochemical dissipation (Kn) parameters in chloroplasts. In addition, some vegetation indexes, such as the pigment-specific simple ratio (PSSRc), anthocyanin reflectance index (ARI1), ratio analysis of reflectance spectra (RARS), and structurally insensitive pigment index (SIPI), are highly correlated with morphological parameters and pigment levels, while PRI, moisture stress index (MSI), normalized difference photosynthetic (PVR), fluorescence ratio (FR), and normalized difference vegetation index (NDVI) are associated with photochemical components of photosynthesis. Combined with the JIP test analysis, our results showed that decreased damage to energy transfer in the electron transport chain is correlated with the accumulation of carotenoids, anthocyanins, flavonoids, and phenolic compounds in the leaves. Phenomenological energy flux modelling shows the highest changes in the photosynthetic apparatus based on PRI and SIPI when analyzed with Pearson's correlation, the hyperspectral vegetation index (HVI) algorithm, and the partial least squares (PLS) to select the most responsive wavelengths. These findings are significant for monitoring nonuniform leaves, particularly when leaves display high variation in pigment profiling in variegated and colorful leaves. This is the first study on the rapid and precise detection of morphological, biochemical, and photochemical changes combined with vegetation indexes for different optical spectroscopy techniques. [ABSTRACT FROM AUTHOR]

Photosystem‐II (PSII) is a multi‐subunit protein complex that harvests sunlight to perform oxygenic photosynthesis. Initial light‐activated charge separation takes place at a reaction centre consisting of four chlorophylls and two pheophytins. Understanding the processes following light excitation remains elusive due to spectral congestion, the ultrafast nature, and multi‐component behaviour of the charge‐separation process. Here, using advanced computational multiscale approaches which take into account the large‐scale configurational flexibility of the system, we identify two possible primary pathways to radical‐pair formation that differ by three orders of magnitude in their kinetics. The fast (short‐range) pathway is dominant, but the existence of an alternative slow (long‐range) charge‐separation pathway hints at the evolution of redundancy that may serve other purposes, adaptive or protective, related to formation of the unique oxidative species that drives water oxidation in PSII. [ABSTRACT FROM AUTHOR]

Photosystem‐II (PSII) is a multi‐subunit protein complex that harvests sunlight to perform oxygenic photosynthesis. Initial light‐activated charge separation takes place at a reaction centre consisting of four chlorophylls and two pheophytins. Understanding the processes following light excitation remains elusive due to spectral congestion, the ultrafast nature, and multi‐component behaviour of the charge‐separation process. Here, using advanced computational multiscale approaches which take into account the large‐scale configurational flexibility of the system, we identify two possible primary pathways to radical‐pair formation that differ by three orders of magnitude in their kinetics. The fast (short‐range) pathway is dominant, but the existence of an alternative slow (long‐range) charge‐separation pathway hints at the evolution of redundancy that may serve other purposes, adaptive or protective, related to formation of the unique oxidative species that drives water oxidation in PSII. [ABSTRACT FROM AUTHOR]

Low temperature (LT) during the grain-filling stage is an important factor that affects the source–sink relationship and leads to yield loss in maize (Zea mays L). In this study, field and pot trials were conducted to investigate the effects of LT during the grain-filling stage on leaf photosynthesis, antioxidant system, hormones, and grain yield of waxy maize cultivars Suyunuo 5 (S5) and Yunuo 7 (Y7). The results showed that LT treatment inhibited the chlorophyll biosynthesis and reduced the photosynthetic pigment levels during grain-filling stage. Ribulose-1,5-bisphosphate carboxylase and phosphoenolpyruvate carboxylase activities, photosynthetic rate, transpiration rate, and stomatal conductance decreased under LT treatment during the grain-filling stage. Furthermore, LT treatment increased the contents of malondialdehyde and reactive oxygen species, and decreased the activities of catalase, superoxide dismutase, peroxidase, and ascorbate peroxidase in the ear leaves, which accelerated the oxidative damage of leaf. The LT treatment also raised abscisic acid content and reduced indole acetic acid content in the ear leaves during grain-filling stage. The results of field and pot trials were verified by each other, but the field effect was greater than that of pot. Overall, LT treatment reduced the waxy maize dry matter accumulation after silking by affecting the physiological and biochemical processes of leaves, and ultimately decreased grain yield. Low temperature (LT) is an important abiotic stress that seriously affects the production and development of maize (Zea mays L). In this study, two waxy maize hybrids were selected and planted in two experimental environments to determine the dynamic changes in leaf photosynthesis, antioxidant system, hormones, and grain yield under post-silking LT stress. This study can be used as a reference for waxy maize to develop adaptation strategies under future climate conditions. [ABSTRACT FROM AUTHOR]

In connection with global warming, the study of plant adaptation to climate change, resistance to lack of moisture and high temperatures becomes relevant. Meteorological and phenological observations prove that a change in temperature conditions leads to an earlier start of vegetation and a lengthening of the growing season in all investigated gooseberry varieties. To assess the functional state of the photosynthetic apparatus of plants, a minimally invasive instrumental method of determining the intensity of chlorophyll fluorescence in plant leaves, adapted to work on the domestic photofluorimeter "Floratest", was used. Based on the results of the analysis of the parameters of the chlorophyll fluorescence induction curves (Fo, Fpl, Fmax, Ft) and the comparison of the coefficients for these values (Kpl, K1, K2), it was established that Fo and Kpl are the most informative. A strong correlation dependence of the indicator of the background level of fluorescence at the time of full opening of the shutter (Fo) was established. The value of Fо correlates positively with indicators of the moisture regime, negatively – with temperature indicators. Correlations between the fluorescence growth index and the variable (Kpl) showed the opposite: the largest positive correlation was observed with mean maximum temperature, the smallest with precipitation. On the basis of mathematical analysis and modeling of the obtained FIC curves and indicators of agro-climatic conditions, the values of the maximum temperature and the minimum amount of precipitation, which are critical for the functioning of the gooseberry photosynthetic apparatus, were determined. Such a study makes it possible to evaluate the course of photochemical reactions associated with the work of plant photosystems according to standard coefficients of photochemical activity, which have already been tested in numerous works of domestic researchers on a wide range of agricultural crops. [ABSTRACT FROM AUTHOR]

Studies on leaf development and photosynthetic characteristics of Salvia miltiorrhiza in different understory habitats can provide a theoretical basis for better implementation of understory combined management. This study analyzed the leaf phenotypic and photosynthetic characteristics of S. miltiorrhiza in three habitats of Pinus massoniana plantations: edge (LY), canopy gap (LX), and understory (LN). Based on the results, the leaf length and width, petiole length, leaf circumference, and specific leaf area of S. miltiorrhiza were ranked as LX＞LY＞LN. The chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll (Chl t), and carotenoid (Car) contents of S. miltiorrhiza were ranked as LY＞LN＞LX, with significant differences. Diurnal variation of the net photosynthesis rates (Pn) in the S. miltiorrhiza leaves in LX and LY display double-peak curves with the apparent siesta phenomenon, mainly due to a stomatal limitation that was not observed in LN. Lower light compensation point(Lcp), higher light saturation point(Lsp), lower dark respiration rate (Rd), higher daily average (Pn), and higher maximum net photosynthetic rate(Pmax) of S. miltiorrhiza in LX indicate that S. miltiorrhiza had a wider ecological amplitude to light in LX than that in the other habitats. These results suggest that LX has a higher concentration of organic matter, making it a more suitable habitat for S. miltiorrhiza [ABSTRACT FROM AUTHOR]

Manganese (Mn) plays an essential role in plant growth; however, excessive Mn is toxic to plants. Polygonum lapathifolium Linn. was tested as a novel Mn-hyperaccumulating species in our previous study, but the underlying mechanisms of this hyperaccumulation are poorly understood. A hydroponic experiment with (8 mmol L−1) and without additional Mn (CK) was established to explore the possible mechanisms through the effects on photosynthesis-related physiological characteristics and metabolomics. The results showed that additional Mn increased plant biomass, photosynthesis, and stomatal conductance related to increases in the effective photochemical quantum yield of photosystem II and relative electron transport rate (P < 0.05). The results from liquid chromatography–mass spectrometry revealed 56 metabolites differentially accumulated between the plants composing these two groups. Metabolites were enriched in 20 metabolic pathways at three levels (environmental information processing, genetic information processing, and metabolism), of which five metabolic pathways were associated with significant or extremely significant changes (P < 0.05). These five enriched pathways were ABC transporters (environmental information processing), aminoacyl-tRNA biosynthesis (genetic information processing), biosynthesis of amino acids , d-arginine and d-ornithine metabolism , and arginine biosynthesis (metabolism). Flavonoids may play a key role in Mn tolerance, as they accumulated more than 490-fold, and the relationship between flavonoids and Mn tolerance needs to be studied in the future. A hydroponic experiment with (8 mmol L−1) and without manganese was established to explore the mechanisms of manganese tolerance of Polygonum lapathifolium Linn via the effects on photosynthesis and metabolism. The results showed that manganese increased plant biomass, photosynthesis, and stomatal conductance. Moreover, among 1022 metabolites, 56 were significantly differentially accumulated, and flavonoids may be the key to the high tolerance of P. lapathifolium. The increased energy and photosynthates from photosynthesis were not allocated to amino acid synthesis. [ABSTRACT FROM AUTHOR]

SUMMARY: Seed longevity, the capacity to remain alive during dry storage, is pivotal to germination performance and is essential for preserving genetic diversity. It is acquired during late maturation concomitantly with seed degreening and the de‐differentiation of chloroplasts into colorless, non‐photosynthetic plastids, called eoplasts. As chlorophyll retention leads to poor seed performance upon sowing, these processes are important for seed vigor. However, how these processes are regulated and connected to the acquisition of seed longevity remains poorly understood. Here, we show that such a role is at least provided by ABSCISIC ACID INSENSITIVE 4 (ABI4) in the legume Medicago truncatula. Mature seeds of Mtabi4 mutants contained more chlorophyll than wild‐type seeds and exhibited a 75% reduction in longevity and reduced dormancy. MtABI4 was necessary to stimulate eoplast formation, as evidenced by the significant delay in the dismantlement of photosystem II during the maturation of mutant seeds. Mtabi4 seeds also exhibited transcriptional deregulation of genes associated with retrograde signaling and transcriptional control of plastid‐encoded genes. Longevity was restored when Mtabi4 seeds developed in darkness, suggesting that the shutdown of photosynthesis during maturation, rather than chlorophyll degradation per se, is a requisite for the acquisition of longevity. Indeed, the shelf life of stay green mutant seeds that retained chlorophyll was not affected. Thus, ABI4 plays a role in coordinating the dismantlement of chloroplasts during seed development to avoid damage that compromises the acquisition of seed longevity. Analysis of Mtabi4 Mtabi5 double mutants showed synergistic effects on chlorophyll retention and longevity, suggesting that they act via parallel pathways. [ABSTRACT FROM AUTHOR]

Climate factors strongly impact the growth of grapes and their flavonoid composition, especially due to heat and drought stress. Four varieties—Gelu, Moldova, Purpuriu, and Coarna Neagra—from a Copou vineyard were analyzed to assess the impact of climate change on the anthocyanin concentration in grapes and total chlorophyll content of the leaves, and find possible correlations between these parameters during the two studied years, such as to raise producer awareness regarding the climate impact on table grape vine growth. Moldova and Purpuriu show adaptation to a slight temperature increase above the normal average and also to a water deficit, with increased concentrations of anthocyanins of up to three times. The Moldova variety accumulated low amounts of chlorophyll pigments in most analyzed development phases, indicating a negative correlation between these pigments. Coarna neagra exhibited an increase of the foliar pigments, a variety that proved to be less valuable from the point of view of anthocyanin content. Positive correlations were found between the anthocyanin and chlorophyll concentrations in the case of Gelu, Moldova, and Coarna neagra cultivars during the latter phase of the fruit development, whereas the water deficit in the second year induced negative correlations during fruit development and at the time of harvest for all studied varieties except Moldova. [ABSTRACT FROM AUTHOR]