Search

Xero-halophytes are the salt-tolerant plants of dry habitats that adapt efficient strategies to endure extreme salt and water fluctuations. This study elucidated the adaptations related to PSII photochemistry, photoprotection, and photoinhibition in six C4 xero-halophytes (Atriplex stocksii , Haloxylon stocksii , Salsola imbricata, Suaeda fruticosa, Desmostachya bipinnata , and Saccharum griffithii) grown in their native habitats. Chlorophyll a fluorescence quenching measurements suggested that S. imbricata and H. stocksii maintained efficient PSII photochemistry by downregulating heat dissipation and keeping a high fraction of open PSII centres that indicates plastoquinone (PQ) pool oxidation. Fluorescence induction kinetics revealed that S. imbricata demonstrated the highest performance index of PSII excitation to the reduction of end electron acceptors. S. fruticosa sustained photochemical efficiency through enhanced dissipation of excess energy and a low fraction of open PSII centres, indicating PQ reduced state. The large light-harvesting antenna size, deduced from the chlorophyll a / b ratio in S. fruticosa apparently led to the superior performance index of PSII excitation to the reduction of intersystem electron carriers. A. stocksii retained more open PSII centres with responsive non-photochemical quenching to safely dissipate excess energy. Despite maintaining the highest pigment contents and stoichiometry, A. stocksii remained lowest in both performance indices. The grass species D. bipinnata and S. griffithii kept fewer PSII centres open during photoinhibition, as evidenced by downregulation of PSII operating efficiency. The results provide insights into the differential modulation of PSII photochemical efficiency through dynamic control of photoprotective energy dissipation, PQ pool redox states, and photoinhibitory shutdown in these xero-halophytes. Photochemical adaptations of six C4 xero-halophytes reveal diverse strategies to endure salt and water fluctuations in native habitats. Variations in photochemistry, photoprotection, and photoinhibition indicate modulation of PSII photochemical efficiency. Different xero-halophytes exhibit distinct mechanisms for maintaining photochemical efficiency through dynamic control of plastoquinone pool redox states, excess energy dissipation, and shutdown mechanisms in response to environmental challenges. [ABSTRACT FROM AUTHOR]

Coastal dunes are characterised by strong gradients of abiotic stress, typically increasing in severity from inland areas towards the shoreline. Thus, dune gradients represent unique opportunities to study intraspecific responses to environmental changes and to investigate which factors drive community change. This study aims to examine functional trait variation in two coexisting species in response to environmental changes along a dune gradient in NW Spain. Trait convergence was also investigated and compared between both ends of the gradient. We measured functional leaf traits related to plant efficiency in the use of light, water and nutrients, also possible stressors (salt content and pH) and availability of limiting resources (water and nutrients) in the soil. Most soil variables showed changes following a non‐directional gradient. Differences in soil variables were site specific and depended on growth of the study species. Structural and functional traits depended on species and/or plant position on the gradient, except for effective quantum yield of PSII and leaf δ15N. The pattern of variation was mostly directional for reflectance indices related to leaf physiology. Multivariate analyses showed significant interspecific differences in the set of traits they exhibited along positions in the gradient. Species also differed in the combination of traits selected under given environmental conditions. Coexisting species display a specific set of traits that reflects different strategies to environmental stress. Our study highlights the overly simplistic nature of some previous studies that assume dune gradients are monotonically directional, without considering that these gradients may be differentially modified by species activity. [ABSTRACT FROM AUTHOR]

Alpine habitats are regarded as particularly vulnerable to the effects of climate change. On one hand, global warming is supposed to contributes to alpine environments becoming less stressful. On the other hand, altered snowpack due to warmer temperatures can intensify the stress in these habitats. The presence of non‐native plants on some of these habitats is due to the facilitative effects exerted by native nurse plants, becoming an additional threat. According to the stress gradient hypothesis the importance of facilitative interactions with nurse species is expected to diminish as environmental harshness decreases due to climate change yet remains important if climate change heightens the stress in alpine habitats. However, the responses also depend on climate change's impact on the nurse species. We conducted an experimental warming experiment in the Andes of the central Chile to assess the effects of warmer temperatures on the growth, reproduction and photochemical efficiency of the cushion nurse plant Azorella madreporica. Further we performed a cushion removal experiment involving three native species (Gamocarpha ventosa, Nocaccea magellanica and Rytidosperma pictum) and two non‐native species (Cerastium arvense and Taraxacum officinale) to assess whether facilitative interactions changed with warming. We expected that under warmer conditions facilitation continued be important for the native species but decreased for the non‐natives as the latter are abundant at warmer low elevations. We found that warmer conditions increased the photochemical efficiency and growth of the nurse cushions. Removal of cushions resulted in high mortality rates for all species. However, under warmer conditions, native species exhibited lower survival rates, whereas non‐natives showed no significant changes compared to control groups. In summary, warmer temperatures were beneficial for the nurses maintaining the importance of facilitative interactions for native species, but not for the non‐natives. [ABSTRACT FROM AUTHOR]

Abstract In contemporary floriculture, particularly within the cut flower industry, there is a burgeoning interest in innovative methodologies aimed at enhancing the aesthetic appeal and prolonging the postharvest longevity of floral specimens. Within this context, the application of nanotechnology, specifically the utilization of silicon and selenium nanoparticles, has emerged as a promising approach for augmenting the qualitative attributes and extending the vase life of cut roses. This study evaluated the impact of silicon dioxide (SiO2-NPs) and selenium nanoparticles (Se-NPs) in preservative solutions on the physio-chemical properties of ‘Black Magic’ roses. Preservative solutions were formulated with varying concentrations of SiO2-NPs (25 and 50 mg L−1) and Se-NPs (10 and 20 mg L−1), supplemented with a continuous treatment of 3% sucrose. Roses treated with 20 mg L−1 Se-NPs exhibited the lowest relative water loss, highest solution uptake, maximum photochemical performance of PSII (Fv/Fm), and elevated antioxidative enzyme activities. The upward trajectory of hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels in petals was mitigated by different levels of SiO2 and Se-NPs, with the lowest H2O2 and MDA observed in preservatives containing 50 mg L−1 SiO2- and 20 mg L−1 Se-NPs at the 15th day, surpassing controls and other treatments. Extended vase life and a substantial enhancement in antioxidative capacity were noted under Se and Si nanoparticles in preservatives. The levels of total phenols, flavonoids, and anthocyanin increased during the vase period, particularly in the 50 and 20 mg L−1 Se-NPs and SiO2-NPs. Petal carbohydrate exhibited a declining trend throughout the longevity, with reductions of 8% and 66% observed in 20 mg L−1 Se-NPs and controls, respectively. The longest vase life was achieved with Se-NPs (20 mg L−1), followed by SiO2-NPs (50 mg L−1) up to 16.6 and 15th days, respectively. These findings highlight the significant potential of SiO2- and Se-NPs in enhancing the vase life and physiological qualities of ‘Black Magic’ roses, with SiO2-NPs showing broad-spectrum efficacy.

Creeping bentgrass (Agrostis stolonifera) is an excellent cool-season turfgrass that is widely used in urban gardening, landscaping, and golf turf. Triennial field experiments from 2017 to 2019 were conducted to investigate effects of the foliar application of chitosan (CTS), γ-aminobutyric acid (GABA), or sodium chloride (NaCl) on mitigating summer bentgrass decline (SBD) and exploring the CTS, GABA, or NaCl regulatory mechanism of tolerance to summer heat stress associated with changes in chlorophyll (Chl) loss and photosynthetic capacity, osmotic adjustment (OA), oxidative damage, and cell membrane stability. The findings demonstrated that persistent ambient high temperatures above 30 °C during the summer months of 2017, 2018, and 2019 significantly reduced the turf quality (TQ), Chl content, photochemical efficiency of PSII (Fv/Fm and PIABS), leaf relative water content, and osmotic potential (OP) but significantly increased electrolyte leakage (EL) and the accumulations of free proline, water-soluble carbohydrate (WSC), hydrogen peroxide (H2O2), and malondialdehyde (MDA). The foliar application of CTS, GABA, or NaCl could significantly alleviate SBD, as reflected by improved TQ and delayed Chl loss during hot summer months. Heat-induced declines in Fv/Fm, PIABS, the net photosynthetic rate (Pn), the transpiration rate (Tr), and water use efficiency (WUE) could be significantly mitigated by the exogenous application of CTS, GABA, or NaCl. In addition, the foliar application of CTS, GABA, or NaCl also significantly improved the accumulations of free proline and WSC but reduced the EL, OP, and H2O2 content and the MDA content in leaves of creeping bentgrass in favor of water and redox homeostasis in summer. Based on the comprehensive evaluation of the subordinate function value analysis (SFVA), the CTS had the best effect on the mitigation of SBD, followed by GABA and NaCl in 2017, 2018, and 2019. The current study indicates that the foliar application of an appropriate dose of GABA, CTS, or NaCl provides a cost-effective strategy for mitigating SBD. [ABSTRACT FROM AUTHOR]

Chlorophyll a fluorescence parameters related to PSII photochemistry, photoprotection and photoinhibition were investigated in four C3 plant species growing in their natural habitat: Prosopis juliflora; Abutilon indicum; Salvadora persica; and Phragmites karka. This study compared the light reaction responses of P. juliflora, an invasive species, with three native co-existing species, which adapt to varying water deficit and high salt stress. Chlorophyll a fluorescence quenching analyses revealed that P. juliflora had the highest photochemical quantum efficiency and yield, regulated by higher fraction of open reaction centres and reduced photoprotective energy dissipation without compromising the integrity of photosynthetic apparatus due to photoinhibition. Moreover, the elevated values of parameters obtained through polyphasic chlorophyll a fluorescence induction kinetics, which characterise the photochemistry of PSII and electron transport, highlighted the superior performance index of energy conservation in the transition from excitation to the reduction of intersystem electron carriers for P. juliflora compared to other species. Enhanced pigment contents and their stoichiometry in P. juliflora apparently contributed to upregulating fluxes and yields of energy absorbance, trapping and transport. This enhanced photochemistry, along with reduced non-photochemical processes, could explain the proclivity for invasion advantage in P. juliflora across diverse stress conditions. [ABSTRACT FROM AUTHOR]

Pineapple is a tropical fruit with high demand by the fruit market in Brazil. Fruits of the cultivar ´Turiaçu` stans out in local consumer markets due to its excellent quality. The objective of this work was to evaluate ecophysiological responses of ´Turiaçu` pineapple plants at the vegetative and reproductive stages to soil fertilization and crop location, and their effects in fruit yield. The study was conducted in the cities of São Luís and Turiaçu, MA, Brazil. Plants under mineral and organic fertilization in two locations, São Luís and Turiaçu, and in two seasons, dry and rainy season, were evaluated during dry and rainy seasons. Chlorophyll index, photochemical efficiency, gas exchange, and fruit yield were evaluated. The pineapple plants presented decrease in the photosynthetic activity, at both developmental stages and in both seasons, when grown in São Luís. The CO2 photosynthetic assimilation decreased. The PSI and PSII activity, according with photosynthetic index, was more sensitive at the reproductive than at the vegetative stage. The organic fertilization was not appropriate for the ´Turiaçu` pineapple crops, regardless of the crop location. The fruit yields were 54.4% and 57.9% lower in São Luís, under mineral and organic fertilization, respectively. Thus, the ecophysiology of ´Turiaçu` pineapple was more affected by water availability than by soil fertility in the municipality of Turiaçu. [ABSTRACT FROM AUTHOR]

Low temperatures largely determine the geographic limits of plant species by reducing survival and growth. Inter-specific differences in the geographic distribution of mangrove species have been associated with cold tolerance, with exclusively tropical species being highly cold-sensitive and subtropical species being relatively cold-tolerant. To identify species-specific adaptations to low temperatures, we compared the chilling stress response of two widespread Indo-West Pacific mangrove species from Rhizophoraceae with differing latitudinal range limits— Bruguiera gymnorhiza (L.) Lam. ex Savigny (subtropical range limit) and Rhizophora apiculata Blume (tropical range limit). For both species, we measured the maximum photochemical efficiency of photosystem II (F v/ F m) as a proxy for the physiological condition of the plants and examined gene expression profiles during chilling at 15 and 5 °C. At 15 °C, B. gymnorhiza maintained a significantly higher F v/ F m than R. apiculata. However, at 5 °C, both species displayed equivalent F v/ F m values. Thus, species-specific differences in chilling tolerance were only found at 15 °C, and both species were sensitive to chilling at 5 °C. At 15 °C, B. gymnorhiza downregulated genes related to the light reactions of photosynthesis and upregulated a gene involved in cyclic electron flow regulation, whereas R. apiculata downregulated more RuBisCo-related genes. At 5 °C, both species repressed genes related to CO2 assimilation. The downregulation of genes related to light absorption and upregulation of genes related to cyclic electron flow regulation are photoprotective mechanisms that likely contributed to the greater photosystem II photochemical efficiency of B. gymnorhiza at 15 °C. The results of this study provide evidence that the distributional range limits and potentially the expansion rates of plant species are associated with differences in the regulation of photosynthesis and photoprotective mechanisms under low temperatures. [ABSTRACT FROM AUTHOR]

The C3–CAM (crassulacean acid metabolism) intermediate species Yucca gloriosa L. is invading coastal dunes in central Italy, causing a loss in biodiversity and habitat. In order to investigate its competitive success, a number of ecophysiological traits were analysed: CAM activity (through carbon isotope composition, δ13C, and cell acidification), photochemical efficiency of PSII (operating and maximum photosystem II quantum yield), stomatal conductance, relative water content, and succulence index (SI). Analyses were conducted over the course of one year, to assess yucca's response to seasons and the shoreline-inland ecological gradient. The species displayed high physiological plasticity, a factor that might prove decisive in enhancing carbon fixation and water-use efficiency across the seasons, and accordingly its level of invasiveness. Temperature seemed crucial in controlling photosynthetic metabolism, a fact borne out by seasonal changes seen in δ13C and SI. Some stress symptoms appeared in winter, including a slight reduction of photochemical performance, and the shoreline–inland ecological gradient did not have any significant effects. All the plants analysed were intermediate C3–CAM: given that yucca cannot reproduce sexually in Europe, the entire population of the area studied might conceivably share the same carbon fixation pathway. The results obtained may help afford a better understanding of the ecophysiological features of Y. gloriosa in a Mediterranean dunal ecosystem, along with the dynamics of the invasion process, allowing a more efficient approach to be adopted in programmes for managing this environment. [ABSTRACT FROM AUTHOR]

The Turiaçu pineapple cultivar produces fruits of high organoleptic value but has few biotechnological studies on seedling production. However, conventional in vitro propagation can affect the photosynthetic potential of plants when transferred to the field, thus mitigating measures should be undertaken to solve this limitation, for example by decreasing carbohydrate concentration in the growth medium, adopting bioreactors of temporary immersion with forced ventilation, and using gas permeable membranes in the culture flask. The present work focused on evaluating the growth and development of plantlets from Ananas comosus [L]. Merr. cultivar Turiaçu, an important but neglected pineapple cultivar, under different sucrose concentrations and cultivation systems. For that, the impact of the photomixotrophic and photoautotrophic growth on morphophysiological responses of plants and survival during the ex vitro acclimatization was assessed. The plants were grown in four cultivation systems: permanent immersion system with sealed flasks (PIS-SF); permanent immersion system with natural ventilation (PIS-NV); single-flask temporary immersion bioreactors (TIS-PF); and twin-flasks temporary immersion bioreactors (TIS-RALM), combined with sucrose concentrations (0, 5.0, 15.0, and 30.0 g L−1). The results indicate that Turiaçu plants have photoautotrophic potential in vitro, as the photochemical efficiency of the plants increased in cultivation systems with TIS –RALM gas exchange without the addition of sucrose. Furthermore, it also improved the performance and hardening of plants in ex vitro conditions, which constitutes a crucial step towards the diffusion of this cultivar. [ABSTRACT FROM AUTHOR]

Drought is one of the main environmental factors affecting crop growth, and breeding drought-tolerant cultivars is one of the most economic and effective ways of increasing yields and ensuring sustainable agricultural production under drought stress. To facilitate the breeding of drought-tolerant wheat, this study was conducted to evaluate genotypic differences in the drought tolerance of 334 wheat genotypes collected from China and Australia with the aim of screening for drought-tolerant and -sensitive genotypes and to elucidate the corresponding physiological mechanisms. A hydroponic-air experiment (roots exposed to air for 7 h/d and continued for 6 d) showed significant genotypic differences in shoot and root dry weights among the genotypes. The relative shoot and root dry weights, expressed as the percentage of the control, showed a normal distribution, with variation ranges of 20.2–79.7% and 32.8–135.2%, respectively. The coefficients of variation were in the range of 18.2–22.7%, and the diversity index was between 5.71 and 5.73, indicating a rich genetic diversity among the wheat genotypes for drought tolerance. Using phenotypic differences in relative dry weights in responses to drought stress, 20 of each of the most drought-tolerant and drought-sensitive genotypes were selected; these were further evaluated in pot experiments (watering withheld until the soil moisture content reached four percent). The results showed that the trends in drought tolerance were consistent with the hydroponic-air experiment, with genotypes W147 and W235 being the most drought-tolerant and W201 and W282 the most sensitive. Significant genotypic differences in water use efficiency in response to drought were observed in the pot experiment, with the drought-tolerant genotypes being markedly higher and the two sensitive genotypes being no different from the control. A marked increase in bound water content in the drought stress plants was observed in the two drought-tolerant genotypes, while a decrease occurred in the free water. The reductions in photochemical efficiencies of PSII, transpiration rates, net photosynthesis rates, chlorophyll contents and stomatal conduction in the drought-sensitive genotypes W201 and W282 under drought stress were higher than the two tolerant genotypes. This study provides a theoretical guide and germplasm for the further genetic improvement of drought tolerance in wheat. [ABSTRACT FROM AUTHOR]

Unlocking how coral endosymbionts (Symbiodiniaceae) regulate the susceptibility of corals to thermal stress-induced bleaching has been the focus of experimental heat stress studies on laboratory-maintained isolates for over 30 years. Multiple protocols to induce heat stress have been used, but the extent to which data can be reconciled across protocols remains unknown. We therefore first analysed past published heat stress studies on Symbiodiniaceae (Jan 1980–Jan 2023) to identify the range of protocols (ramping rate derived from time taken to reach the target heat stress temperatures from the initial ambient temperature, time retained under the target heat stress temperature, etc.) commonly used for experimentation. Temperature differences between ambient and maximum experimental temperatures spanned from 3 °C to 17 °C (mean = 6.8 °C), and only 41% of all studies reported a ramping rate, ranging from instantaneous to 0.02 °C/h (mean = 0.62 °C/h). Experiment length at the treatment temperature varied from < 24 h to > 2 months. We next experimentally quantified if the rate of heating impacted the observed physiological outcome for three Symbiodiniaceae taxa with differences in heat tolerance—Durusdinium trenchii, Breviolum psygmophilum and Breviolum minutum. Five experimental treatments were performed with different temperature ramping rates from 26 °C to 32 °C: 1 °C/1 h, 1 °C/12 h, 1 °C/1 d, 1 °C/2 d and 1 °C/3 d, spanning relatively acute to chronic. Changes in physiology were quantified daily as the maximum photochemical efficiency (Fv/Fm). Heating commonly induced decreases in Fv/Fm, and the change between the start and end of experiment (∆Fv/Fm) linearly increased with ramping rates. Our data suggests that slower ramping exacerbates thermal stress, though with varying magnitude across taxa as B. minutum, and D. trenchii proved less resilient than B. pysgmophilum. We discuss how these outcomes potentially impact the capacity to integrate biological responses observed from past experiments and highlights the need for more standardised experimental protocols. [ABSTRACT FROM AUTHOR]

Creeping bentgrass (Agrostis stolonifera) is an excellent cool-season turfgrass that is widely used in urban gardening, landscaping, and golf turf. Triennial field experiments from 2017 to 2019 were conducted to investigate effects of the foliar application of chitosan (CTS), γ-aminobutyric acid (GABA), or sodium chloride (NaCl) on mitigating summer bentgrass decline (SBD) and exploring the CTS, GABA, or NaCl regulatory mechanism of tolerance to summer heat stress associated with changes in chlorophyll (Chl) loss and photosynthetic capacity, osmotic adjustment (OA), oxidative damage, and cell membrane stability. The findings demonstrated that persistent ambient high temperatures above 30 °C during the summer months of 2017, 2018, and 2019 significantly reduced the turf quality (TQ), Chl content, photochemical efficiency of PSII (Fv/Fm and PIABS), leaf relative water content, and osmotic potential (OP) but significantly increased electrolyte leakage (EL) and the accumulations of free proline, water-soluble carbohydrate (WSC), hydrogen peroxide (H2O2), and malondialdehyde (MDA). The foliar application of CTS, GABA, or NaCl could significantly alleviate SBD, as reflected by improved TQ and delayed Chl loss during hot summer months. Heat-induced declines in Fv/Fm, PIABS, the net photosynthetic rate (Pn), the transpiration rate (Tr), and water use efficiency (WUE) could be significantly mitigated by the exogenous application of CTS, GABA, or NaCl. In addition, the foliar application of CTS, GABA, or NaCl also significantly improved the accumulations of free proline and WSC but reduced the EL, OP, and H2O2 content and the MDA content in leaves of creeping bentgrass in favor of water and redox homeostasis in summer. Based on the comprehensive evaluation of the subordinate function value analysis (SFVA), the CTS had the best effect on the mitigation of SBD, followed by GABA and NaCl in 2017, 2018, and 2019. The current study indicates that the foliar application of an appropriate dose of GABA, CTS, or NaCl provides a cost-effective strategy for mitigating SBD.

Aluminum (Al) toxicity is a major limiting factor for plant growth and crop production in acidic soils. This study aims to investigate the effects of γ-aminobutyric acid (GABA) priming on mitigating acid-Al toxicity to creeping bentgrass (Agrostis stolonifera) associated with changes in plant growth, photosynthetic parameters, antioxidant defense, key metabolites, and genes related to organic acids metabolism. Thirty-seven-old plants were primed with or without 0.5 mM GABA for three days and then subjected to acid-Al stress (5 mmol/L AlCl3·6H2O, pH 4.35) for fifteen days. The results showed that acid-Al stress significantly increased the accumulation of Al and also restricted aboveground and underground growths, photosynthesis, photochemical efficiency, and osmotic balance, which could be effectively alleviated by GABA priming. The application of GABA significantly activated antioxidant enzymes, including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase, to reduce oxidative damage to cells under acid-Al stress. Metabolomics analysis demonstrated that the GABA pretreatment significantly induced the accumulation of many metabolites such as quinic acid, pyruvic acid, shikimic acid, glycine, threonine, erythrose, glucose-6-phosphate, galactose, kestose, threitol, ribitol, glycerol, putrescine, galactinol, and myo-inositol associated with osmotic, antioxidant, and metabolic homeostases under acid-Al stress. In addition, the GABA priming significantly up-regulated genes related to the transportation of malic acid and citric acid in leaves in response to acid-Al stress. Current findings indicated GABA-induced tolerance to acid-Al stress in relation to scavenging of reactive oxygen species, osmotic adjustment, and accumulation and transport of organic metabolites in leaves. Exogenous GABA priming could improve the phytoremediation potential of perennial creeping bentgrass for the restoration of Al-contaminated soils. [ABSTRACT FROM AUTHOR]

Introduction: The use of drought tolerant genotypes is one of the main strategies proposed for coping with the negative effects of global warming in dry lands. Trichloris crinita is a native forage grass occupying extensive arid and semi-arid regions in the American continent, and used for range grazing and revegetation of degraded lands. Methods: To identify drought-tolerant genotypes and possible underlying physiological mechanisms, this study investigated drought tolerance in 21 genetically diverse T. crinita genotypes under natural field conditions. The accessions were grown under irrigated (control) and drought conditions for 84 days after initiation of the drought treatment (DAIDT), which coincided with flowering initiation. Various morpho-physiological traits were monitored, including total-, foliage-, and root biomass yield, dry matter partitioning to individual plant organs (roots, leaves, stems, and panicles), total leaf area, chlorophyll content, photochemical efficiency of photosystem II, stomatal conductance, and number of panicles per plant. Results and discussion: Broad and significant variation (p<0.001) was found among the accessions for all the traits. Three highly tolerant and three very sensitive accessions were identified as the most contrasting materials, and their responses to drought stress were confirmed over two years of experiments. Under prolonged drought conditions (84 DAIDT), the tolerant accessions were generally more productive than the rest for all the biomass yield components analyzed, and this was associated with a postponed and more attenuated decrease in variables related to the plant photosynthetic activity, such as stomatal conductance, chlorophyll content, and photochemical efficiency. In contrast to previous findings, our data indicate no direct relationship between drought tolerance and the level of aridity in the accessions natural habitats, but rather suggest genetic heterogeneity and ample variation for drought tolerance in T. crinita natural populations derived from a particular location or environment. Also, having low total and forageable biomass yield, or increased biomass allocation to the roots (i.e., lower foliage/root ratio), under optimal water availability, were not associated with greater drought tolerance. The drought-tolerant accessions identified are of value for future genetic research and breeding programs, and as forage for range grazing and revegetation in arid regions. [ABSTRACT FROM AUTHOR]

IntroductionThe use of drought tolerant genotypes is one of the main strategies proposed for coping with the negative effects of global warming in dry lands. Trichloris crinita is a native forage grass occupying extensive arid and semi-arid regions in the American continent, and used for range grazing and revegetation of degraded lands.MethodsTo identify drought-tolerant genotypes and possible underlying physiological mechanisms, this study investigated drought tolerance in 21 genetically diverse T. crinita genotypes under natural field conditions. The accessions were grown under irrigated (control) and drought conditions for 84 days after initiation of the drought treatment (DAIDT), which coincided with flowering initiation. Various morpho-physiological traits were monitored, including total-, foliage-, and root biomass yield, dry matter partitioning to individual plant organs (roots, leaves, stems, and panicles), total leaf area, chlorophyll content, photochemical efficiency of photosystem II, stomatal conductance, and number of panicles per plant.Results and discussionBroad and significant variation (p

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Extreme seawater temperatures are linked to increasingly frequent cnidarian bleaching, a breakdown of the symbiosis between host and endosymbiotic dinoflagellates. This can be driven by several anthropogenic stressors, of which seawater warming is a major and frequent one. It remains unclear whether this is caused by intrinsic properties of the host or exclusively by the symbiont. This study investigates the response to elevated temperatures of dinoflagellate symbionts in and ex hospite, particularly to find out whether thermal tolerance differs between endosymbionts and free-living micro-algae. Maximum quantum yield of photosystem II (Fv/Fm) and symbiont cell density were measured in seven different cnidarian species and five cultures of isolated endosymbionts subjected to temperatures of 26°C (control), 30°C and 34°C for 21 days. Isolated dinoflagellate cells showed a susceptibility to elevated temperatures of 30°C, evidenced by a decrease in photochemical efficiency and cell density of the cultures, as well as a progressive disintegration of cellular structures and loss of pigmentation of all but two cultures during the first week of exposure. Bleaching of coral holobionts at 30°C could be explained by reduced density of algae cells in host tissue. This effect was particularly evident in soft corals. Exposure to 34°C resulted in drastic bleaching of stony coral species, anemones and jellyfish, and even the death of soft corals. Data from this study show different responses to elevated thermal conditions across several species and different genera of symbionts and emphasize the important role of dinoflagellate symbionts in the holobiont response to elevated seawater temperatures. [ABSTRACT FROM AUTHOR]

Drought is one of the main environmental factors affecting crop growth, and breeding drought-tolerant cultivars is one of the most economic and effective ways of increasing yields and ensuring sustainable agricultural production under drought stress. To facilitate the breeding of drought-tolerant wheat, this study was conducted to evaluate genotypic differences in the drought tolerance of 334 wheat genotypes collected from China and Australia with the aim of screening for drought-tolerant and -sensitive genotypes and to elucidate the corresponding physiological mechanisms. A hydroponic-air experiment (roots exposed to air for 7 h/d and continued for 6 d) showed significant genotypic differences in shoot and root dry weights among the genotypes. The relative shoot and root dry weights, expressed as the percentage of the control, showed a normal distribution, with variation ranges of 20.2–79.7% and 32.8–135.2%, respectively. The coefficients of variation were in the range of 18.2–22.7%, and the diversity index was between 5.71 and 5.73, indicating a rich genetic diversity among the wheat genotypes for drought tolerance. Using phenotypic differences in relative dry weights in responses to drought stress, 20 of each of the most drought-tolerant and drought-sensitive genotypes were selected; these were further evaluated in pot experiments (watering withheld until the soil moisture content reached four percent). The results showed that the trends in drought tolerance were consistent with the hydroponic-air experiment, with genotypes W147 and W235 being the most drought-tolerant and W201 and W282 the most sensitive. Significant genotypic differences in water use efficiency in response to drought were observed in the pot experiment, with the drought-tolerant genotypes being markedly higher and the two sensitive genotypes being no different from the control. A marked increase in bound water content in the drought stress plants was observed in the two drought-tolerant genotypes, while a decrease occurred in the free water. The reductions in photochemical efficiencies of PSII, transpiration rates, net photosynthesis rates, chlorophyll contents and stomatal conduction in the drought-sensitive genotypes W201 and W282 under drought stress were higher than the two tolerant genotypes. This study provides a theoretical guide and germplasm for the further genetic improvement of drought tolerance in wheat.

Copyright of Revista Ciência Agronômica is the property of Revista Ciencia Agronomica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Ambiente e Água is the property of Revista Ambiente e Agua and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In Saudi Arabia, poinciana (Delonix regia) trees are afflicted by dieback disease, manifesting symptoms that can lead to complete defoliation and, ultimately, the demise of trees in advanced stages. To investigate the dieback symptoms, samples were collected from branches at the transition zone. Identification of fungal isolates involved the assessment of colony and spore morphology, as well as PCR amplification and sequencing of the internal transcribed spacer (ITS) gene regions. The predominant fungus isolated was Alternaria tenuissima. Chlorophyll a fluorescence quenching and polyphasic fluorescence induction kinetics were conducted to assess the photochemical and nonphotochemical processes of Photosystem II (PSII) in stem barks affected by dieback. The dieback disease significantly reduced chlorophyll content, potentially hindering PSII performance in terms of maximum photochemical efficiency, quantum yield, electron flux, and photoprotection. These findings suggest that compromised photochemistry and photoprotection render poinciana trees inoculated by dieback less efficient in utilizing light energy and more susceptible to photoinhibition. Additionally, this study implies the use of non-invasive chlorophyll fluorescence techniques as a phenotyping tool for assessing photoprotective and photoinhibitory responses of stems to dieback stress. • Dieback in poinciana twigs is caused by fungal pathogen Alternaria tenuissima. • Reduction in chlorophyll during dieback impedes photosystem II photochemistry. • Dieback disease inhibits photoprotection and enhances photoinhibition. • Chlorophyll fluorescence technique helps to detect early dieback symptoms in stem. [ABSTRACT FROM AUTHOR]

Aluminum (Al) toxicity is a major limiting factor for plant growth and crop production in acidic soils. This study aims to investigate the effects of γ-aminobutyric acid (GABA) priming on mitigating acid-Al toxicity to creeping bentgrass (Agrostis stolonifera) associated with changes in plant growth, photosynthetic parameters, antioxidant defense, key metabolites, and genes related to organic acids metabolism. Thirty-seven-old plants were primed with or without 0.5 mM GABA for three days and then subjected to acid-Al stress (5 mmol/L AlCl3·6H2O, pH 4.35) for fifteen days. The results showed that acid-Al stress significantly increased the accumulation of Al and also restricted aboveground and underground growths, photosynthesis, photochemical efficiency, and osmotic balance, which could be effectively alleviated by GABA priming. The application of GABA significantly activated antioxidant enzymes, including superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase, to reduce oxidative damage to cells under acid-Al stress. Metabolomics analysis demonstrated that the GABA pretreatment significantly induced the accumulation of many metabolites such as quinic acid, pyruvic acid, shikimic acid, glycine, threonine, erythrose, glucose-6-phosphate, galactose, kestose, threitol, ribitol, glycerol, putrescine, galactinol, and myo-inositol associated with osmotic, antioxidant, and metabolic homeostases under acid-Al stress. In addition, the GABA priming significantly up-regulated genes related to the transportation of malic acid and citric acid in leaves in response to acid-Al stress. Current findings indicated GABA-induced tolerance to acid-Al stress in relation to scavenging of reactive oxygen species, osmotic adjustment, and accumulation and transport of organic metabolites in leaves. Exogenous GABA priming could improve the phytoremediation potential of perennial creeping bentgrass for the restoration of Al-contaminated soils.

Reef-building corals usually form a symbiotic relationship with various photosynthetic dinoflagellates, which may determine the physiology and stress tolerance of their hosts. The mechanisms governing symbiont dynamics are still poorly understood, but may be driven by temperature. Therefore, we performed indoor experiments to examine the photochemical efficiency and symbiont dynamics in the coral Pocillopora damicornis with thermo-sensitive Cladocopium (PdC) or thermo-tolerant Durusdinium (PdD) under 6-day temperature stress and after 90-day post-stress recovery. Regardless of the symbiont type, photochemical damage was induced by both heat and cold stress. We observed PdC with greater photodamage had a faster increase in the proportion of Durusdinium when exposed to heat or cold stress, whereas an inverse shuffling to Cladocopium in both PdC and PdD after the recovery period. This is the first record of symbiont shuffling from the originally dominant Durusdinium to Cladocopium in adult corals under laboratory conditions and the degree of symbiont shuffling was highly correlated with the photodamage. Overall, our findings suggest that symbiont shuffling can act as a critical mechanism allowing corals to rapidly adjust to environmental changes, which has implications for the capacity of corals to prevail in oceans with greater temperature fluctuations in the future.

The endemic Moroccan species Argania spinosa is considered the most grazed tree species in its distribution area. Since grazing exerts an important effect on plant performances, we attempted to explore the impact of grazing on A. spinosa. Thus, we performed a comparative field experiment where seasonal variations of gas exchange, photochemical efficiency, relative water content, photosynthetic pigment content, and stomatal features were assessed in grazed and ungrazed trees. The net photosynthetic rate was increased in grazed trees in spring and autumn, the favorable seasons. Enhancement of photosynthetic performance may be due to the high stomatal conductance registered in grazed trees. This mechanism may compensate for the lost leaf area, in order to recover from grazing stress. In addition, grazed trees exhibit a better photochemical efficiency, use water more economically and show lower oxidative stress. However, results obtained in summer show that the compensation mechanism could be limited by summer drought. Since the key to preserving the future of forests is sustainable forest management, our results suggest that proper grazing management can be a control tool to increase plant performance and improve species resilience. [ABSTRACT FROM AUTHOR]

In many regions, nitrogen (N) deficiency limits pepper cultivation, presenting significant cultivation challenges. This study investigates the impact of N deficiency and silicon (Si) supplementation on physiological responses and antioxidant modulation in pepper plants, focusing particularly on the homeostasis of carbon (C), nitrogen, and phosphorus (P), and their effects on growth and biomass production. Conducted in a factorial design, the experiment examined pepper plants under conditions of N sufficiency and deficiency, with and without Si supplementation (0.0 mM and 2.0 mM). Results showed that N deficiency sensitizes pepper plants, leading to increased electrolyte leakage (39.59%) and disrupted C, N, and P homeostasis. This disruption manifests as reductions in photosynthetic pigments (-64.53%), photochemical efficiency (-14.92%), and the synthesis of key metabolites such as total free amino acids (-86.97%), sucrose (-53.88%), and soluble sugars (-39.96%), ultimately impairing plant growth. However, Si supplementation was found to alleviate these stresses. It modulated the antioxidant system, enhanced the synthesis of ascorbic acid (+30.23), phenolic compounds (+33.19%), and flavonoids (+7.52%), and reduced cellular electrolyte leakage (-25.02%). Moreover, Si helped establish a new homeostasis of C, N, and P, optimizing photosynthetic and nutritional efficiency by improving the utilization of C (+17.46%) and N (+13.20%). These Si-induced modifications in plant physiology led to increased synthesis of amino acids (+362.20%), soluble sugars (+51.34%), and sucrose (77.42%), thereby supporting enhanced growth of pepper plants. These findings elucidate the multifaceted biological roles of Si in mitigating N deficiency effects, offering valuable insights for more sustainable horticultural practices., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Vertical distributions of phytoplankton in the Arctic Ocean are characterized by a very narrow subsurface chlorophyll maximum (SCM) layer formed every summer after the sea ice retreats. Despite the prevalence of this narrow SCM layer, phytoplankton photosynthetic response to climate change remains to be elucidated. Here, we examined the photophysiological properties of phytoplankton in the SCM layer in the northern Chukchi Sea during the summers of 2015–2018. There was a significant difference in the SCM depth between the northwestern and northeastern Chukchi Sea determined by the distribution of Pacific Summer Water (PSW) around the SCM layer (34 ± 14 m vs. 49 ± 10 m, respectively). The maximum quantum yield of photochemistry in photosystem II (Fv/Fm) in the SCM phytoplankton was high (Fv/Fm ≥ 0.54) and similar in both regions until 2016; however, since then, Fv/Fm in the northeastern Chukchi Sea has decreased by approximately 10%. This decrease was accompanied by a marked decrease in the fraction of microplankton, which are known to be susceptible to nutrient limitation. This result suggests a reduction in nitrogen availability in the SCM layer in the northeastern Chukchi Sea. Meanwhile, the maximum electron transfer rate (ETRmax) did not have a significant relationship with the nitrogen availability and phytoplankton community size structure in the SCM layer; however the improved light conditions (with an approximately two-fold increase in the relative ratio of surface PAR reaching the SCM layer) increased ETRmax by up to 30% in the SCM phytoplankton in the northwestern Chukchi Sea. Therefore, these results provide a better understanding of how changes in nitrogen and light availability could affect phytoplankton photosynthesis and primary production in the Arctic Ocean.

Highlights: Salinity tolerance among traditional varieties of cowpea is variable. High net photosynthesis is observed in cowpea-tolerant varieties under salt stress. The decrease in photosynthesis is caused by stomatal restriction and low photochemical efficiency. Cowpea varieties are similar in photochemical efficiency and photochemical quenching. The decrease in pod number and seeds per pod are the main effects of salinity on cowpea production. Cowpea is the main subsistence crop—protein source—for the Brazilian semi-arid region. The use of salt-stress-tolerant varieties can improve crop yields. We evaluated the effect of irrigation with brackish water on the growth, photosynthetic responses, production, and tolerance of fifteen traditional varieties of cowpea. The experiment was conducted in randomized blocks, in a 15 × 2 factorial scheme, composed of 15 traditional varieties of cowpea and two salinity levels of irrigation water (0.5 and 4.5 dS m−1), with five replicates. Plants were grown in pots containing 10 dm3 of soil for 80 days. The reduction in the photosynthetic rate of cowpea varieties occurs mainly due to the decrease in stomatal conductance caused by salt stress. Salt stress increased the electron transport rate and photochemical quenching of cowpea varieties, but stress-tolerant varieties increased the CO2 assimilation rate and instantaneous carboxylation efficiency. The Ceará, Costela de Vaca, Pingo de Ouro, Ovo de Peru, and Sempre Verde varieties are tolerant to salt stress. Salt stress decreases 26% of the production of tolerant varieties to salt stress and 54% of susceptible varieties. The present findings show the existence of variability for saline stress tolerance in traditional varieties of cowpea and that Ceará, Costela de Vaca, Pingo de Ouro, and Ovo de Peru varieties are more suitable for crops irrigated with saline water. [ABSTRACT FROM AUTHOR]

The summer climate in Maritime Antarctica is characterised by high humidity and cloudiness with slightly above zero temperatures. Under such conditions, photosynthetic activity is temperature-limited and plant communities are formed by a few species. These conditions could prevent the operation of the photoprotective xanthophyll (VAZ) cycle as low irradiance reduces the excess of energy and low temperatures limit enzyme activity. The VAZ cycle regulates the dissipation of the excess of absorbed light as heat, which is the main mechanism of photoprotection in plants. To test whether this mechanism operates dynamically in Antarctic plant communities, we characterised pigment dynamics under natural field conditions in two representative species: the moss Polytrichum juniperinum and the grass Deschampsia antarctica. Pigment analyses revealed that the total VAZ pool was in the upper range of the values reported for most plant species, suggesting that they are exposed to a high degree of environmental stress. Despite cloudiness, there was a strong conversion of violaxanthin (V) to zeaxanthin (Z) during daytime. Conversely, the dark-induced enzymatic epoxidation back to V was not limited by nocturnal temperatures. In contrast with plants from other cold ecosystems, we did not find any evidence of overnight retention of Z or sustained reductions in photochemical efficiency. These results are of interest for modelling, remote sensing and upscaling of the responses of Antarctic vegetation to environmental challenges. [ABSTRACT FROM AUTHOR]

Spermine (SPM) is involved in response to abiotic stress in plants, but the potential role of SPM in regulating senescence has not been well documented. Objectives of this study were to examine the effect of changes in endogenous polyamines (PAs) by SPM application on improving heat tolerance of creeping bentgrass (Agrostis stolonifera) and explore the SPM-regulated senescence associated with alterations of water and oxidative balance, photosynthesis, and heat shock proteins under heat stress. The results showed that persistent high temperature caused severe oxidative damage and significant decreases in chlorophyll (Chl) content, photosynthetic efficiency, and leaf water content leading to premature senescence in creeping bentgrass, as reflected by a significant upregulation of transcriptions of senescence-associated genes (AsSAG39, Ash36, and Asl20). The improvement of endogenous spermidine (SPD) and SPM content induced by SPM application could significantly alleviate heat stress damage to creeping bentgrass through maintaining higher Chl content, net photosynthetic rate, photochemical efficiency, and performance index on absorption basis, promoting osmotic adjustment ability and antioxidant enzyme (superoxid dismutase, catalase, peroxidase, and ascorbate peroxidase) activities to enhance the scavenging capacity of reactive oxygen species, and upregulating transcriptions of heat shock protein (HSP) genes (HSP90-5, HSP90.1-b1, HSP82, HSP70, HSP26.7, HSP17.8, and HSP12) helping to maintain normal synthesis and functions of proteins under high temperature stress, thereby delaying heat-induced leaf senescence. These findings reveal an important role of PAs in regulating senescence in perennial plants exposed to a high temperature environment.

Copyright of Revista Caatinga is the property of Revista Caatinga and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Alteration of ploidy in one particular plant species often influences their environmental adaptation. Warm-season bermudagrass is widely used as forage, turfgrass, and ground-cover plant for ecological remediation, but exhibits low shade tolerance. Adaptive responses to shade stress between triploid hybrid bermudagrass cultivars ["Tifdwarf" (TD), "Tifsport" (TS), and "Tifway" (TW)] and tetraploid common bermudagrass cultivar "Chuanxi" (CX) were studied based on changes in phenotype, photosynthesis, and secondary metabolites in leaves and stems. Shade stress (250 luminance, 30 days) significantly decreased stem diameter and stem internode length, but did not affect the leaf width of four cultivars. Leaf length of CX, TD, or TW showed no change in response to shade stress, whereas shade stress significantly elongated the leaf length of TS. The CX and the TS exhibited significantly higher total chlorophyll (Chl), Chl a, carotenoid contents, photosynthetic parameters [PSII photochemical efficiency (Fv/Fm), transpiration rate, and stomatal conductance] in leaves than the TW and the TD under shade stress. The CX also showed a significantly higher performance index on absorption basis (PIABS) in leaf and net photosynthetic rate (Pn) in leaf and stem than the other three cultivars under shade stress. In addition, the TS maintained higher proantho cyanidims content than the TW and the TD after 30 days of shade stress. Current results showed that tetraploid CX exhibited significantly higher shade tolerance than triploid TD, TS, and TW mainly by maintaining higher effective photosynthetic leaf area, photosynthetic performance of PSI and PSII (Pn and Fv/Fm), and photosynthetic pigments as well as lower Chl a/b ratio for absorption, transformation, and efficient use of light energy under shade stress. For differential responses to shade stress among three triploid cultivars, an increase in leaf length and maintenance of higher Fv/Fm, gas exchange, water use efficiency, carotenoid, and proanthocyanidin contents in leaves could be better morphological and physiological adaptations of TS to shade than other hybrid cultivars (TD and TW). [ABSTRACT FROM AUTHOR]

The use of effluent from fish farming in the greenhouse increases the availability of water and reduces the risk of environmental contamination due to improper disposal. Therefore, a study in a greenhouse was carried out to evaluate the effects of fertigation utilizing fish farming effluent at different phenological stages of cherry tomato. Plants of cherry tomato were fertigated with fish farming effluent (E) alternated with tap water (W) at the four phenological stages of the crop (growth, flowering, fruit formation and ripening). The growth, gas exchange, chlorophyll a fluorescence, chloroplast pigments, electrolyte leakage, production and postharvest quality were evaluated. The fertigation with fish farming effluents did not reduce the growth of tomato plants. The fertirrigated plants with fish farming effluents obtained photosynthetic rates and photochemical efficiency similar or superior to the control. There was no interference on photochemical quenching when the plants were fertigated with fish farming effluents. When applied at the flowering stage, fish farming effluent reduces the average fruit weight and increases acidity. For greenhouse cultivation, each application of fish farming effluents, two successive applications of tap water are required. Novelty statement: Use of fish farming effluent did not compromise the growth and photosynthetic activity of cherry tomato plants. Cherry tomato production was compromised when the effluent was applied during growth, flowering and, beginning of fruit set. The fish farming effluent can be used in irrigation without yield losses if alternating with tap water. [ABSTRACT FROM AUTHOR]

The scarce availability of good quality water for irrigation in semi-arid regions leads to the reuse of waters, such as reject brine. Associated with this, the use of alternatives, such as hydroponic cultivation in substrates suitable for the development of profitable crops, such as watermelon, a species considered moderately sensitive to salinity, will allow new opportunities for communities assisted by desalination plants. An experiment was conducted in a plastic greenhouse to evaluate the growth, physiological responses, yield, and fruit quality of 'Sugar Baby' mini-watermelon cultivated in a hydroponic system with reject brine from desalination plants and different substrates. The experimental design was randomized blocks, with treatments arranged in a 5 × 4 factorial scheme, corresponding to five mixtures of reject brine (9.50 dS m−1) and tap water (0.54 dS m−1) applied to mini-watermelon plants, in an open hydroponic system, with four types of substrate and four replicates, with two plants per plot. Mini-watermelon plants grown in coconut fiber substrate showed the best growth and production. On the other hand, washed sand was the substrate that most hampered the development of plants in all mixtures. The use of reject brine to prepare the nutrient solution reduced the growth and production of mini-watermelon, mainly in mixtures with salinity above 4.00 dS m−1. The changes in gas exchange caused by salt stress in mini-watermelon were of stomatal nature. Mini-watermelon has high energy stability under conditions of salt stress. [ABSTRACT FROM AUTHOR]

We determined the chronic effects of dehydration on the photochemical efficiency of a cultivated brown alga, Undaria pinnatifida (Alariaceae, Laminariales), in young sporophytes as cultivated sporelings. The effective quantum yields of photosystem II (ΔF/Fm′) at 50% humidity decreased markedly after 20 min of emersion and dropped almost zero after 60 min of emersion; the values did not restore even after subsequent 1-day immersion. The decreasing values coincided with a decrease in absolute water content of less than 40%. However, under 99% humidity up to 5-day emersion, the ΔF/Fm′ well remained and the last state exhibited a similar level to the initial value after a 48-h emersion at 20 °C and after 72 h of emersion at 10 °C, suggesting that the thalli were not truly dehydrated under saturated humidity and that photosynthetic activity was maintained for several days even without immersion in seawater. In addition, the subsequent growth of young sporophytes exposed to transportation storage stress featuring (1) immersed in seawater with aeration (ST1), (2) those without aeration (ST2), and (3) wrapped in paper towels moistened with seawater (ST3) revealed that the sporophytes exposed at lower temperature exhibited a higher subsequent growth than those at a higher temperature. The subsequent growth of ST3 was lower than ST1; however, the values of ST3 were higher than those of ST2 more than 12 °C, associating with poor seawater quality without aeration. These results indicated that the maintenance of moisture in the alga at low temperatures might be essential for the transportation of the sporelings. [ABSTRACT FROM AUTHOR]

Alteration of ploidy in one particular plant species often influences their environmental adaptation. Warm-season bermudagrass is widely used as forage, turfgrass, and ground-cover plant for ecological remediation, but exhibits low shade tolerance. Adaptive responses to shade stress between triploid hybrid bermudagrass cultivars [“Tifdwarf” (TD), “Tifsport” (TS), and “Tifway” (TW)] and tetraploid common bermudagrass cultivar “Chuanxi” (CX) were studied based on changes in phenotype, photosynthesis, and secondary metabolites in leaves and stems. Shade stress (250 luminance, 30 days) significantly decreased stem diameter and stem internode length, but did not affect the leaf width of four cultivars. Leaf length of CX, TD, or TW showed no change in response to shade stress, whereas shade stress significantly elongated the leaf length of TS. The CX and the TS exhibited significantly higher total chlorophyll (Chl), Chl a, carotenoid contents, photosynthetic parameters [PSII photochemical efficiency (Fv/Fm), transpiration rate, and stomatal conductance] in leaves than the TW and the TD under shade stress. The CX also showed a significantly higher performance index on absorption basis (PIABS) in leaf and net photosynthetic rate (Pn) in leaf and stem than the other three cultivars under shade stress. In addition, the TS maintained higher proantho cyanidims content than the TW and the TD after 30 days of shade stress. Current results showed that tetraploid CX exhibited significantly higher shade tolerance than triploid TD, TS, and TW mainly by maintaining higher effective photosynthetic leaf area, photosynthetic performance of PSI and PSII (Pn and Fv/Fm), and photosynthetic pigments as well as lower Chl a/b ratio for absorption, transformation, and efficient use of light energy under shade stress. For differential responses to shade stress among three triploid cultivars, an increase in leaf length and maintenance of higher Fv/Fm, gas exchange, water use efficiency, carotenoid, and proanthocyanidin contents in leaves could be better morphological and physiological adaptations of TS to shade than other hybrid cultivars (TD and TW).

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cold-stressed leaves possess an elevated risk of photodamage due to an inefficient photosynthetic apparatus during winter conditions. Recovery of cold-stressed coffee seedlings treated with different concentrations of nitrogen applied as foliar urea sprays [control (0), 5, 10, 20, and 40 mM], was investigated under optimum growth chamber conditions (25/20°C) for three months. Concentrations of nitrogen and photosynthetic pigments in the leaves increased with increasing concentration of the foliar sprays up to 20 mM. This was accompanied with a recovery of the photosynthetic apparatus and increased net carbon assimilation rate. In addition, 10 and 20 mM-treated plants also had the highest maximal efficiency of PSII compared to their lower or higher nitrogen concentration treated counterparts. Conversely, these plants contained lower concentrations of 5-caffeoylquinic acid, mangiferin, trigonelline, and caffeine than control plants. We concluded therefore that foliar sprays of the appropriate nitrogen concentration were adequate for recuperating the photosynthetic apparatus and improved the photosynthetic performance of the cold-stressed coffee seedlings.

The aim of the work was to investigate thermal stress effect on photosynthetic activity of common buckwheat. Seedlings of common buckwheat were exposed to 20°C (control) and 30°C (thermal stress). The research involved the Polish cultivar 'Panda' and strain PA15 and determined kinetics of chlorophyll a fluorescence (Chlf), leaf gas exchange, soluble carbohydrate (SC) content in donor leaves, electrolyte leakage as a parameter of cell membrane permeability, and amount of abscisic acid and jasmonates. In 'Panda' and PA15 plants grown at 30°C, most of Chlf parameters improved. 'Panda' plants grown at 30°C demonstrated a higher increase in net photosynthetic rate, lower transpiration rate, and smaller SC reduction than those of PA15 strain. At this temperature, 'Panda' leaves accumulated greater amounts of jasmonates than that of the control. We concluded that studied genotypes demonstrated disparate responses to thermal stress, but for both, 30°C is more favourable temperature for vegetative growth than 20°C.

The use of pearl millet (Pennisetum glaucum) for biomass production has increased significantly across much of the Brazilian Midwest. This region is characterized by weathered soils with low pH and low in fertility. Phosphorus and micronutrients are particularly low in these soils. Therefore, studies evaluating the management of micronutrients, especially manganese (Mn), are essential to improve the productivity of pear millet. This study aimed to assess the effect of Mn fertilization on the physiology traits and biomass production of pearl millet. The study was conducted in a greenhouse using a completely randomized design with four replications. Five Mn rates were applied (0 (control), 3, 6, 9, and 12 kg ha−1, as MnO) at planting. Biometric (plant height, stem diameter, and leaf area index) and physiological quality (cholorpyll index, transpiration, photosynthesis, leaf CO2 concentration, and stomatal conductance) were evaluated 30 and 65 days after emergence (DAE). Millet biomass, at harvest, was also evaluated. Pearl millet response to Mn fertilization was significant on measurements taken 65 DAE, with exception of leaf area index. Regardless of time of measurements, applying 6 kg Mn ha−1 provided the best results at the end of the experiments. Increased Mn rates, above 6 kg ha−1, caused a decrease in the physiological traits of millet but did not affect the biomass production. Moreover, greater Mn utilization efficiency by plants was found at the 6 kg ha−1 Mn rate, suggesting that this is the recommended rate for improving biomass production of pear millet grown under similar soil and weather conditions. [ABSTRACT FROM AUTHOR]

γ-Aminobutyric acid (GABA) is a non-protein amino acid involved in regulating various environmental adaption in plants. Twenty-six-day-old creeping bentgrass plants were treated with or without GABA (0.5 mM) and then exposed to heat stress (35/30 °C, day/night) for 25 days. Results showed that exogenous GABA application significantly increased endogenous GABA accumulation and alleviated heat-caused growth inhibition and water loss during heat stress. GABA-treated creeping bentgrass maintained significantly lower carbonyl content, malondialdehyde content, and electrolyte leakage, but exhibited higher total antioxidant capacity and antioxidant enzyme activities (SOD, CAT, POD, APX, and DR) than untreated plants under heat stress. Heat stress significantly decreased chlorophyll content, stomatal conductance, transpiration rate, net photosynthesis, and water use efficiency. However, GABA application effectively alleviated these heat-induced negative effects in creeping bentgrass. In addition, exogenous GABA further increased the expression of heat-induced HSPs (HSP12, HSP1 7.8, HSP26.7, HSP70, HSP82, HSP90.1-A1, HSP90.1-B1 , and HSP90-5) and HSFs (HSFA-2c, HSFA-2d, HSFA-6a, HSFB-2b , and HSFC-2b) and also further increased the abundance of HSP70, HSP90-1, and HSP101 in leaves of creeping bentgrass under heat stress. These results indicated that GABA alleviated heat-induced oxidative damage and chlorophyll loss through enhancing antioxidant capacity. GABA-treated creeping bentgrass maintained higher photosynthesis in leaves contributing to higher accumulation of water soluble carbohydrates for osmotic balance and energy supply under heat stress. GABA-regulated thermotolerance could be involved in upregulating HSF pathways in creeping bentgrass. • GABA alleviates heat-induced damage and chlorophyll loss through enhancing antioxidant capacity in creeping bentgrass. • GABA regulates the accumulation of water soluble carbohydrates for osmotic balance and energy supply under heat stress. • GABA regulates heat shock pathways and the accumulation of heat shock proteins in creeping bentgrass under heat stress. [ABSTRACT FROM AUTHOR]

The effects of temperature, irradiance, and desiccation on the photosynthesis of a cultivated Japanese green alga Caulerpa lentillifera (Caulerpaceae) were determined by a pulse amplitude modulation (PAM)-chlorophyll fluorometer and dissolved oxygen sensors. The photochemical efficiency in the photosystem II (Fv/Fm and ΔF/Fm') during the 72-h temperature exposures (8, 12, 16, 20, 24, 28, 32, 36, and 40°C) was generally stable at 16–32°C but quickly dropped at lower and higher temperatures. The photosynthesis–temperature curve at 200 μmol photons m−2 s−1 also revealed that the maximum gross photosynthesis (GPmax) occurred at 30.7°C (30.5–30.9, 95% highest density credible intervals). Photosynthesis–irradiance curves at 16, 24, and 32°C quickly saturated, then expressed photoinhibition, and revealed that the maximum net photosynthetic rates (NPmax) and saturation irradiance (Ek) were highest at 32°C and lowest at 16°C. Continuous 6-h exposure to irradiances of 200 (low) and 400 (high) μmol photons m−2 s−1 at 16, 24, and 32°C expressed greater declines in their ΔF/Fm' at 16°C, revealing chronic chilling-light stress. The response to continuous desiccation (~480 min) under 50% humidity at 24°C showed that ΔF/Fm' dropped to zero at 480-min aerial exposure, and the treatments of more than 60-min desiccation did not return to the initial level even after 24-h subsequent rehydration in seawater. Likewise, ΔF/Fm' fell when the absolute water content (AWC) of the frond dropped below AWC of 90% and mostly did not return to the initial level even after 24-h subsequent rehydration in seawater, signifying a low tolerance to desiccation. [ABSTRACT FROM AUTHOR]

Phragmites karka (Retz.) Trin. ex Steud. is a pan-tropical, wetland, grass, and this study restricted water availability to P. karka by either low matric potential (water deficit) or low osmotic potential (salinity). Growth, water relations, mineral nutrition, and photosynthesis were compared when plants were irrigated at control (100% water holding capacity WHC), 300 mM NaCl (salinity, at 100% WHC), or water deficit (40% WHC) conditions. Leaf water potential and plant growth decreased substantially under salinity and water deficit. This led to stomatal closure and a decrease in gas exchange with the risk of oxidative injury. Under saline conditions, stress was mitigated by an increased dissipation of absorbed light energy by non-photochemical quenching. Water deficit conditions led to higher PS II quantum yield efficiency. Shoot Na+ toxicity was reduced by 10-fold higher Na+ sequestration in salt-treated roots, and enhanced proline and soluble carbohydrate accumulation in the leaf, compared to the control. Inorganic and organic substances maintained a higher soil-to-plant water gradient in salt-stressed plants compared to drought-stressed plants. P. karka survived in both forms of restricted water via growth plasticity, regulated osmotic and ionic homeostasis, and efficient gas exchange and PSII photochemistry. [ABSTRACT FROM AUTHOR]

Once absorbed by plants, trace elements, such as cadmium, are transported and bioaccumulated in organs and tissues, including seeds. The germination and seedling establishment are sensitive points in plant development and can be impacted by external environmental conditions. However, plants can transmit information to ensure better acclimation of their offspring to conditions similar to those experienced by the parental generation. The aim of this work was to understand the mechanisms of which seeds from four different origins acclimate in adverse environments similar to those in which the mother plant was grown. The experiment was performed with 4 seed origins with distinct accumulation of cadmium (Cd) and manganese (Mn) and 3 conditions (regarding presence or absence of cadmium and manganese) in seeds and seedlings. Seeds were characterized by their germination, and biochemical analyses such as hydrogen peroxide, lipid peroxidation, soluble and reducing sugars, proteins, amino acids and proline, and antioxidant enzymes activity in seeds collected 8 and 24 h of imbibition. Then, seeds were grown in soil for 25 days and sampling for biochemical analyses, cadmium and manganese quantification, chlorophyll a fluorescence and biomass determination. Seeds with higher levels of cadmium performed better in conditions with cadmium through an apparent acclimation mechanism that involved enhanced enzymatic antioxidant system activity and differential soluble and reducing sugar utilization. The effects mainly differed between seeds of the '5 Cd' and '5Cd400Mn' origins, which was also observed in the seedlings. The effects of cadmium and manganese appeared to be specific to the plant origin, causing mainly a reduction in photochemical efficiency, altered electron flux and oxidative stress generation, with plants of different origins also displaying differential mechanisms to cope with the stressful conditions. [Display omitted] • Seeds that accumulate cadmium during formation germinate better in conditions where this trace element is present. • The presence of manganese along with cadmium in substrate promoted less oxidative stress in seed tissues than Cd alone. • Seeds accumulating more Cd and Mn showed varied sugar usage, enhancing germination in conditions with these elements. • Seedlings from high-cadmium seeds showed impaired photochemical efficiency in cadmium and manganese conditions. [ABSTRACT FROM AUTHOR]

Cowpea is the main subsistence crop—protein source—for the Brazilian semi-arid region. The use of salt-stress-tolerant varieties can improve crop yields. We evaluated the effect of irrigation with brackish water on the growth, photosynthetic responses, production, and tolerance of fifteen traditional varieties of cowpea. The experiment was conducted in randomized blocks, in a 15 × 2 factorial scheme, composed of 15 traditional varieties of cowpea and two salinity levels of irrigation water (0.5 and 4.5 dS m−1), with five replicates. Plants were grown in pots containing 10 dm3 of soil for 80 days. The reduction in the photosynthetic rate of cowpea varieties occurs mainly due to the decrease in stomatal conductance caused by salt stress. Salt stress increased the electron transport rate and photochemical quenching of cowpea varieties, but stress-tolerant varieties increased the CO2 assimilation rate and instantaneous carboxylation efficiency. The Ceará, Costela de Vaca, Pingo de Ouro, Ovo de Peru, and Sempre Verde varieties are tolerant to salt stress. Salt stress decreases 26% of the production of tolerant varieties to salt stress and 54% of susceptible varieties. The present findings show the existence of variability for saline stress tolerance in traditional varieties of cowpea and that Ceará, Costela de Vaca, Pingo de Ouro, and Ovo de Peru varieties are more suitable for crops irrigated with saline water.