Leaf Soluble Sugar Research Articles

Impact of abandonment on leaf morphology traits and nutrient utilization strategies of dominant tree seedlings in Moso bamboo forests

The restoration of ecological functions in abandoned Moso bamboo forests facilitates positive succession in evergreen vegetation. Nevertheless, there is a limited understanding regarding the leaf functional traits and nutrient utilization strategies of understory vegetation after abandonment. This study investigated the impact of abandonment duration (9 and 21 years) on leaf morphological traits, soluble sugars characteristics, carbon (C), nitrogen (N), phosphorus (P), and their ratios in dominant tree seedlings (Lithocarpus brevicaudatus and Schima superba) within Moso bamboo forests. Leaf sizes increased significantly with prolonged abandonment in both species, accompanied by a consistent decrease in leaf thickness and leaf tissue density. These morphological indices were more pronounced in L. brevicaudatus compared to S. superba (P < 0.05), and they showed a positive correlation with tree sizes. Moreover, leaf soluble sugars, C, and C: N: P ratios of both tree species decreased over duration abandonment, while N and P contents increased. Specifically, L. brevicaudatus exhibited elevated levels of fructose, glucose, N, and P, whereas S. superba displayed higher sucrose, C, and C: N: P ratios. Our findings reveal that both species, with extended abandonment, enlarged their leaf area and improved carbon utilization, facilitating adaptation to competitive resource habitats. Particularly, L. brevicaudatus exhibited a propensity to augment leaf sizes, as well as N, and P contents, suggesting a strategy to enhance carbon assimilation through additional N and P nutrient supplementation. Conversely, S. superba primarily focused on bolstering carbohydrate reserves, indicating that moderate thinning or pruning of bamboo forests could boost sunlight penetration, along with the appropriate nutrient supplementation. These insights significantly contribute to the scientific understanding necessary for the classification and management of mixed stands in abandoned bamboo forests.

Physio-biochemical responses of rice to smart nitrogen fertilizer nano-hydrogel under drought stress and flooding alternation: An eco-friendly innovative approach to enhance the grain quality

Fertilizer nanohydrogels have been newly introduced to agriculture. Herein, we investigated the effects of smart nitrogen (N) fertilizer nano-hydrogel on rice's physio-biochemical traits and seed quality under different drought stress and flooding conditions. Therefore, a pot experiment was conducted with no N fertilizer delivery 0 g N/kg (NND), with conventional N fertilizer delivery 0.175 g N/kg (CND), and smart N fertilizer delivery 0.175 g N/kg (SND) using three irrigation options: flooding/moderate dryness (FMD, 90% saturation, 30 mm submerged), flooding/sharp dryness (FSD, 70% saturation, 30 mm submerged), and flooding/extreme dryness (FED, 50% saturation, 30 mm submerged). Results showed that rice root's active acquisition area and enzymatic activity were larger in FMD × SND than in FED × NND, as the former combination increased NH4+, NO3−, and TN contents in the soil while the latter reduced their availability. The optimal N nutrition improved the plant cell ultrastructure, and the catalase activity was higher in the FMD × SND (42.0 µg/min) compared to the FED × NND (25.2 µg/min), leading to the alleviation of oxidative cell injury, as verified by lesser radical oxidative sequences and lipid peroxidation. The leaf soluble protein (8.8 mg/g) and sugar (36.9 mg/g) were greater in FMD × SND than in FED × NND (5.3 mg/g), (10.4 mg/g), and (8.3 µg/g h), respectively. Moreover, α-amylase and glutamine synthetase activities were larger in the FMD × SND than in FED × NND. Meanwhile, the FMD × SND resulted in the highest milled rice (87.3%), amylose (17.6%), protein (12.4%), and fatty acids (11.1%). However, the combination of FED × NND led to the lowest milled rice (70.0%), amylose (5.6%), protein (5.3%), and fatty acids (6.6%). This study suggests that the FMD × SND can guarantee physio-biochemical improvements in rice, thereby increasing grain quality.

Soil nutrients determine leaf traits and above-ground biomass in the tropical cloud forest of Hainan Island

Identifying soil characteristics associated with the plant’s resource use and acquisition strategy at different scales could be a crucial step to understanding community assembly and plant strategy. There is an increasing trend that plant functional properties can be an important driver of ecosystem functioning. However, major knowledge gaps exist about how soil abiotic properties, shape species diversity, above-ground biomass (AGB) and plant functional diversity in the Bawangling tropical forest (TCF) of Hainan island. Hence we hypothesized that plant functional traits and above-ground biomass would be strongly associated with soil abiotic factors given their direct relationship to soil resource acquisition and use. Here, we used 12 plant functional traits (FTs), above-ground biomass (AGB), and five soil nutrients in the Bawangling tropical cloud forest of Hainan Island by using a polynomial regression model and multivariate correlations to show relationship and identify how plants allocate their limited resources to adapt to their surroundings. Various phytosociological attributes were assessed and an Importance Value Index (IVI) value was calculated for each species to determine the dominant species. More than half of the total variations could be attributed to interspecific variations in H, DBH, LA, LMA, and LDW. From a taxonomic perspective; we found that species-level variance was more significant for plant functional traits and soil nutrients like TN, AP, TP, and OM. On the other hand, variation in specific stem density (SSD), leaf thickness (LT), leaf phosphorus (LP) and leaf soluble sugar (LS) was an exception for these tendencies. Among soil nutrients, soil nitrogen and phosphorus significantly impact the species and functional traits. Furthermore, the soil AN and TP we also found to have a comparatively strong positive relationship with above-ground biomass (AGB) as compared with other soil nutrients. The morpho-physiological functional traits showed a trade-off between conservative and acquisitive resource usage. These variations suggested that the relationships of functional traits, AGB, and species with soil nutrients mainly AN and TP in tropical cloud forests can directly affect the growth, reproduction, and survival of the species and are beneficial for the species co-existence and maintenance of biodiversity.

Rootstock and Crop Load Effects on ‘Honeycrisp’ Photosynthetic Performance and Carbohydrate Accumulation

Rootstock selection and crop load adjustment are key practices in apple orchard management; nevertheless, the effects of rootstocks and crop load levels on important physiological processes of the scions, such as photosynthetic performance and carbohydrate accumulation, are still unclear. To investigate the impact of different rootstocks and crop load levels on scion photosynthesis and carbohydrate buildup, in 2020, ‘Honeycrisp’ trees grafted on rootstocks ‘G.41’, ‘G.935’, and ‘M.9-T337’ were thinned to low and high crop load levels, and photosynthetic performance and carbohydrate accumulation in leaves and fruit were evaluated. Leaves from ‘G.935’ showed the highest net photosynthesis and electron use efficiency of photosynthesis and the lowest activity for non-net carboxylative processes, all together indicative of enhanced photosynthetic performance. High crop load determined an increase in gas exchange, suggesting a positive feedback of high fruit competition on carbon assimilation. While rootstock ‘M.9-T337’ showed a higher accumulation of starch in leaves, no pattern regarding the composition of leaf-soluble sugars among rootstocks could be identified. Conversely, by the end of the harvest season, leaves from low-cropping trees had higher fructose, glucose, and sorbitol than those from high-cropping trees, but differences in starch content were not significant. Fructose and sorbitol concentrations were affected by rootstock and crop load, respectively. Overall, this study showed that high cropping enhanced photosynthesis in ‘Honeycrisp’ apple and determined lower accumulation of some soluble carbohydrates (fructose, glucose, sorbitol) in leaves. This study also provided insights into how rootstocks affect photosynthetic performance of ‘Honeycrisp’, highlighting ‘G.935’ as the rootstock conferring the highest photosynthetic capacity under the present experimental conditions.

Nitrogen deposition alters drought-induced changes in biomass and nonstructural carbohydrates allocation patterns of Quercus mongolica seedlings

Water and nitrogen (N) are major constraints that affect plant growth and survival. N deposition can enhance plant photosynthetic capacity and drought tolerance. However, the ecophysiological processes of plants in response to N deposition associated with drought stress are unclear. We investigated the allocation patterns of biomass and nonstructural carbohydrates (NSC) among different organs in response to the addition of ammonium nitrate in Mongolian oak seedlings along a drought stress gradient. This study used pot experiment with three levels of N addition (CK: 0, LN: 5 and HN: 10 g N m−2 yr−1) in conjunction with three irrigated water volumes (W0: 36 L, W1: 25 L, reduction 30%, and W2: 18 L, reduction 50 %). The results showed drought stress, resulting in a decreasing trend in photosynthesis, had been reversed by N addition, and trends in water use efficiency also appeared to increase. Similarly, drought caused a decreasing trend in the biomass and the decreases in the ratio of root-to-shoot (R:S) and total biomass at the whole-seedling level. The enhancements in aboveground biomass were induced by N addition regardless of water conditions. Adversely, root biomass appeared to decrease under normal water conditions (W0) and increased under drought stress. In addition, leaf soluble sugar (SS) concentration and leaf SS: starch increased with N addition under W0 and decreased under severe drought (W2). When water and N availability were abundant, the carbon (C) use strategy of Mongolian oak seedlings focused on aboveground growth to get more carbohydrates. However, when water availability was in severe deficit, the C use strategy of seedlings shifted from growth to protection and defense by restoring more carbohydrates in stems or roots to survive the harsh environments, even when N availability was adequate. This study provided new insights into the understanding of C use strategy and drought survival mechanism in response to environmental change.

Remediation potential of biochar and selenium for mitigating chromium-induced stress in spinach to minimize human health risk

The contamination of agricultural soils with metals and metalloids significantly affects crop productivity. The objective of the present study was to investigate how the combined application of biochar and selenium (Se) could mitigate the adverse effects of chromium (Cr) stress on spinach. The effects of selenium (Na2SeO4) (1 mg L − 1) and biochar (5 %, w/w) application both individually and in combination were evaluated on the basis of growth, physio-biochemical and antioxidant potential of spinach grown under Cr stress (100 µM [29.40 mg] using K2Cr2O7 of soil) and without Cr stress as control (0 µM). The results indicated that Cr stress decreased the root length (34.62 %), shoot length (35.32 %), number of leaves (23.18 %), root dry weight (12.00 %), and leaf dry weight (24.36 %) under Cr stress by lowering relative water content (RWC) and chlorophyll concentrations due to increased electrolyte leakage (64.03 %) and the Cr accumulation in leaves. However, the combined application of biochar and Se significantly enhanced the fresh and dry biomass under Cr stress and control conditions. The synergistic effect of Se and biochar partly alleviates the effects of Cr stress in spinach by up-regulating the antioxidant system, reducing lipid peroxidation (60.00 %), increasing leaf soluble sugars (25.22 %), and simultaneously decreasing electrolyte leakage. The combined effect of Se and biochar proved better results as compared to the sole application in minimizing Cr uptake in leaves (52.08 %) and limiting the health risk assessment values. Overall, this study highlights that the combined application of biochar and Se is an innovative and eco-friendly approach to improving the physio-biochemical defense responses against Cr stress in spinach plants.

Drought responsiveness in six wheat genotypes: identification of stress resistance indicators.

Wheat (Triticum aestivum L.) is among the world's most important staple food crops. In the current climate change scenario, a better understanding of wheat response mechanisms to water stress could help to enhance its productivity in arid ecosystems. In this study, water relations, gas exchange, membrane integrity, agronomic traits and molecular analysis were evaluated in six wheat genotypes (D117, Syndiouk, Tunisian durum7 (Td7), Utique, Mahmoudi AG3 and BT) subjected to drought-stress. For all the studied genotypes, drought stress altered leaf area, chlorophyll content, stomatal density, photosynthetic rate and water-use efficiency, while the relative water content at turgor loss point (RWC0) remained stable. Changes in osmotic potential at turgor loss point (Ψπ0), bulk modulus of elasticity (Ɛmax) and stomatal regulation, differed greatly among the studied genotypes. For the drought-sensitive genotypes AG3 and BT, no significant changes were observed in Ψπ0, whereas the stomatal conductance (gs) and transpiration rate (E) decreased under stress conditions. These two varieties avoided turgor loss during drought treatment through an accurate stomatal control, resulting in a significant reduction in yield components. On the contrary, for Syndiouk, D117, Td7 and Utique genotypes, a solute accumulation and an increase in cell wall rigidity were the main mechanisms developed during drought stress. These mechanisms were efficient in enhancing soil water uptake, limiting leaf water loss and protecting cells membranes against leakage induced by oxidative damages. Furthermore, leaf soluble sugars accumulation was the major component of osmotic adjustment in drought-stressed wheat plants. The transcriptional analysis of genes involved in the final step of the ABA biosynthesis (AAO) and in the synthesis of an aquaporin (PIP2:1) revealed distinct responses to drought stress among the selected genotypes. In the resistant genotypes, PIP2:1 was significantly upregulated whereas in the sensitive ones, its expression showed only a slight induction. Conversely, the sensitive genotypes exhibited higher levels of AAO gene expression compared to the resistant genotypes. Our results suggest that drought tolerance in wheat is regulated by the interaction between the dynamics of leaf water status and stomatal behavior. Based on our findings, Syndiouk, D117, Utique and Td7, could be used in breeding programs for developing high-yielding and drought-tolerant wheat varieties.

Effects of Inoculation with Different Plant Growth-Promoting Rhizobacteria on the Eco-Physiological and Stomatal Characteristics of Walnut Seedlings under Drought Stress

Plant growth-promoting rhizobacteria (PGPR) can promote plant growth and induce systemic resistance to biological and abiotic stresses. However, do all PGPR have significant effects in arid environments, and which PGPR have the most optimal effects? This study used a pot experiment to investigate the effects of inoculation with two different PGPR on the physiological and ecological characteristics of walnut (Juglans regia) seedlings under drought stress: Bacillus subtilis GE1, which secretes protease only, and Pseudomonas brassicacearum X123, which secretes protease and indoleacetic acid (IAA). The leaves inoculated with X123 under drought stress had higher net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (gs), especially stomatal length and stomatal width, compared to GE1 inoculation under drought stress. Moreover, inoculation with X123 significantly increased the leaf superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities by 20.84% and 12.41%, respectively, and the gibberellin (GA) and zeatin (ZT) contents by 72.07% and 19.17%, respectively, whereas the leaf soluble sugar and soluble protein contents significantly decreased compared with GE1 inoculation. These results indicated that the effects of GE1 inoculation on the physiological and ecological characteristics of walnut seedling leaves were significantly weaker in comparison with X123 inoculation as a result of its functional characteristics. The application of different PGPR on the drought tolerance of J. regia showed significant differences. Therefore, the selection of appropriate PGPR is key to achieving positive treatment effects under drought conditions.

Effect of Selenium on Growth, Physio-Biochemical and Yield Traits of Lettuce under Limited Water Regimes

Climate change has become one of the most complicated challenges of the twenty-first century. Water scarcity is a significant threat to food security, and climate change has adversely affected the likelihood of extreme events such as drought. Selenium (Se) has been reported to mitigate abiotic stress effects, such as drought, on various plant species. The purpose of the current study was to observe the effects of foliar-applied Se to minimize the detrimental effects of water-deficient conditions. Therefore, this study was designed to evaluate the exogenous application of Se at various levels (0, 3, 6 and 9 mg L−1) on the growth, physio-biochemical attributes and antioxidant defense system of lettuce plants growing under an irrigation water deficit from 85 ± 5% (control) to 35 ± 5% (drought stress). The results revealed that increasing water deficit stress linearly reduced plant growth and biomass by reducing relative water content (19.49%) and chlorophyll contents (23.95%) through increased electrolyte leakage (20.67%). However, foliar-applied Se significantly increased fresh and dry biomass under control and water-stressed conditions. Under drought stress, Se supply increased free proline content and the activities of SOD, POD and CAT in leaf tissues. The exogenous application of Se partly alleviated the effects of drought on lettuce by the upregulation of the antioxidant system and leaf soluble sugars and a simultaneous decrease in electrolyte leakage. This study further suggests that the upregulation of antioxidants and osmoprotectants is positively associated with the drought tolerance of lettuce. In conclusion, the exogenous application of Se (6 mg L−1) has more potential to improve lettuce growth, physiological attributes and modulation of enzymatic antioxidant potential, which can be recommended for use to maximize lettuce productivity and quality in a dry environment. This research provides a promising, technically feasible strategy for mitigating drought stress in order to achieve the Sustainable Development Goals (SDGs) of good health and zero hunger.

The combined effect of seawater salinity and duration on the survival and growth of eelgrass Zostera marina

Abrupt changes in salinity are considered a key cause of seagrass bed degradation. In the study, we first quantified the effects of different combinations of salinity and duration on the responses of Zostera marina shoots in terms of survivorship, morphology, growth and physiology. The recovery potential (recovery of shoots from salinity stress to be returned to original salinity level) of Z. marina shoots was assessed. The LT50 (lethal time that caused an increase in mortality to 50 % of that of the control) and EC50 (effect concentration, i.e., salinity level that caused a decrease in growth to 50 % of that of the control) were calculated to reveal the quantitative relationship between salinity and duration that resulted in limiting effects on the survival and growth of Z. marina shoots. Z. marina shoots were exposed to different combinations of water salinity [20, 25, 30 (control), 35, 40, and 45 PSU] and duration (5, 10, 15 and 20 days), and then the shoots were transferred to the control condition for 30 days under laboratory conditions. The results showed that the survival rate of shoots at the end of recovery was significantly lower than those of shoots at the end of direct salinity stress at the hypersalinity levels of 40 and 45 PSU, indicating that short-term periods of increase in water salinity would lead to long-term effects on the survival of Z. marina shoots. The total leaf area of shoots at the end of recovery was significantly higher than those of shoots at the end of direct salinity stress at salinity levels of 25–35 PSU, indicating a significant recovery potential following the salinity stress. However, a poor recovery potential was found under combinations of hypersalinity (40–45 PSU) and duration of 20 days. Regression analysis revealed that the relationship between salinity and duration was a strong power function that could limit the growth of Z. marina. Pearson correlation analysis showed that the survival and growth of Z. marina shoots exposed to different salinity levels were significantly correlated with leaf soluble sugar contents when the duration was higher than 5 days. This study will further enhance our understanding of seagrass bed degeneration induced by abrupt changes in salinity.

Enhanced Nutrients Removal from Eutrophic Water by Aerobic Denitrifiers Assisting Floating Plants

Accelerated eutrophication is one of the most serious problems confronting freshwater systems worldwide. More effective methods to reduce nutrients from eutrophic water with high nitrogen but low carbon source are now urgently needed. In this study, the methods of floating plant remediation and aerobic denitrification were combined for seeking an effective strategy. Four aerobic denitrifying bacteria were adopted. Each strain was co-cultured with Eichhornia crassipes, and then the effects of different combinations on the removal of nitrogen and phosphorus were compared. Meanwhile, their impacts on the growth and physiological characteristics of plants were also measured. The results showed that the association of aerobic denitrifying bacteria with E. crassipes was effective in enhancing the simultaneous removal of nitrogen and phosphorus. E. crassipes helped bacteria to eliminate the accumulation of nitrites under the condition of limited carbon sources. Cooperation between Rhizobium rosettiformans and E. crassipes exhibited the best remediation performance. The four aerobic denitrifying bacteria increased the plant growth and phosphorus content, and had different effects on the plant root activity, leaf chlorophyll, leaf soluble sugar and leaf soluble protein concentration. Although the overall nutrients removal efficiency was greatly improved by the synergic association, the percentage contribution of plant uptake remained constant.

Interactive effects of elevated temperature and drought on plant carbon metabolism: A meta-analysis.

Elevated temperature (Te ) and drought often co-occur and interactively affect plant carbon (C) metabolism and thus the ecosystem C cycling; however, the magnitude of their interaction is unclear, making the projection of global change impacts challenging. Here, we compiled 107 journal articles in which temperature and water availability were jointly manipulated, and we performed a meta-analysis of interactive effects of Te and drought on leaf photosynthesis (Agrowth ) and respiration (Rgrowth ) at growth temperature, nonstructural carbohydrates and biomass of plants, and their dependencies on experimental and biological moderators (e.g., treatment intensity, plant functional type). Our results showed that, overall, there was no significant interaction of Te and drought on Agrowth . Te accelerated Rgrowth under well-watered conditions rather than under drought conditions. The Te × drought interaction on leaf soluble sugar and starch concentrations were neutral and negative, respectively. The effect of Te and drought on plant biomass displayed a negative interaction, with Te deteriorating the drought impacts. Drought induced an increase in root to shoot ratio at ambient temperature but not at Te . The magnitudes of Te and drought negatively modulated the Te × drought interactions on Agrowth . Root biomass of woody plants was more vulnerable to drought than that of herbaceous plants at ambient temperature, but this difference diminished at Te . Perennial herbs exhibited a stronger amplifying effect of Te on plant biomass in response to drought than did annual herbs. Te exacerbated the responses of Agrowth and stomatal conductance to drought for evergreen broadleaf trees rather than for deciduous broadleaf and evergreen coniferous trees. A negative Te × drought interaction on plant biomass was observed on species-level rather than on community-level. Collectively, our findings provide a mechanistic understanding of the interactive effects of Te and drought on plant C metabolism, which would improve the prediction of climate change impacts.

Effects of 6-Benzylaminopurine Combined with Prohexadione-Ca on Yield and Quality of Chrysanthemum morifolium Ramat cv. Hangbaiju

Increasing shoot branch numbers of Chrysanthemum morifolium Ramat cv. Hangbaiju (Hangbaiju) is crucial for producing high flower yields. Pot experiments were designed to evaluate the effects of foliar application of 6-benzylaminopurine (6-BA) combined with prohexadione-Ca (Pro-Ca) on the yield and quality of Hangbaiju flowers. Foliar application of 6-BA combined with Pro-Ca typically increased leaf chlorophyll content and decreased leaf soluble sugar and soluble protein contents throughout the floral organ growth phase. At the bud formation phenophase stage (August), the contents of gibberellin (GA), indole-3-acetic acid (IAA), and zeatin (ZA) decreased (except for GA content in the 10 mg L−1 6-BA combined with 100 mg L−1 Pro-Ca treatment), but abscisic acid (ABA) content increased. The yield of Hangbaiju flowers was found higher in plants treated with foliar application of 6-BA combined with Pro-Ca. Higher yields were found in the 6-BA5 + Ca100 and 6-BA10 + Ca100 treatments than in the 6-BA5 + Ca50 and 6-BA10 + Ca50 treatments, and the highest yield was observed in the 6-Ba5 + Ca100 treatment both in 2019 and 2020. Nutritional indices such as soluble sugar, soluble protein, total amino acid, and water extract increased, and medicinal indices such as flavonoid, total phenolics, chlorogenic acid, cynaroside, and 3,5-dicaffeoyl quinic acid slightly decreased after foliar application of 6-BA combined with Pro-Ca; however, they were all higher than the standards recorded in the Chinese Pharmacopeia. Overall, foliar application of 6-BA combined with Pro-Ca could increase the yield and nutritional quality of Hangbaiju flowers, enhancing its tea quality.

Responses of tree growth, leaf area and physiology to pavement in Ginkgo biloba and Platanus orientalis.

Trees growing on paved lands endure many environmental stresses in the urban environment. However, the morphological and physiological mechanisms underlying tree adaptation to pavement in the field are less known. In this study, we investigated 40 sites where Ginkgo biloba and Platanus orientalis grow on adjacent pairs of paved and vegetated plots in parks and roadsides in Beijing, China. Relative to the vegetated land, the mean increments in the diameter at breast height and height in the paved land were significantly decreased by 44.5% and 31.9% for G. biloba and 31.7% and 60.1% for P. orientalis, respectively. These decreases are related to both the decrease in assimilation products due to the reductions in leaf area, leaf total nitrogen content, and chlorophyll content and the increase in energy cost due to the synthesis of more soluble sugar and proline for mitigating stress. The increase in leaf soluble sugar content, proline content, and δ13C indicated that trees could adapt to the paved land through the regulation of osmotic balance and the enhancement of water-use efficiency. Piecewise structural equation models showed that trees growing on the paved land are stressed by compounding impacts of the leaf morphological and physiological changes. Therefore, it is critical to explore the complex response of plant morphological and physiological traits to the pavement-induced stress for improving tree health in urban greening.

Exposure to strong irradiance exacerbates photoinhibition and suppresses N resorption during leaf senescence in shade-grown seedlings of fullmoon maple (Acer japonicum).

Leaves of fullmoon maple (Acer japonicum) turn brilliant red with anthocyanins synthesis in autumn. Based on field observations, autumn coloring mainly occurs in outer-canopy leaves exposed to sun, whereas inner-canopy leaves remain green for a certain longer period before finally turn yellowish red with a smaller amount of anthocyanins. Here, we hypothesized that outer-canopy leaves protect themselves against photooxidative stress via anthocyanins while simultaneously shading inner canopy leaves and protecting them from strong light (holocanopy hypothesis). To test this hypothesis, we investigated photoinhibition and leaf N content during autumn senescence in leaves of pot-grown seedlings of fullmoon maple either raised under shade (L0, ≈13% relative irradiance to open) or transferred to full sunlight conditions on 5th (LH1), 12th (LH2), or 18th (LH3) Oct, 2021. Dry mass-based leaf N (Nmass) in green leaves in shade-grown seedlings was ≈ 30 mg N g-1 in summer. Nmass in shed leaves (25th Oct to 1st Nov) was 11.1, 12.0, 14.6, and 10.1 mg N g-1 in L0, LH1, LH2, and LH3 conditions, respectively. Higher Nmass was observed in shed leaves in LH2, compared to other experimental conditions, suggesting an incomplete N resorption in LH2. Fv/Fm after an overnight dark-adaptation, measured on 19th Oct when leaf N was actively resorbed, ranked L0: 0.72 > LH3: 0.56 > LH1: 0.45 > LH2: 0.25. As decreased Fv/Fm indicates photoinhibition, leaves in LH2 condition suffered the most severe photoinhibition. Leaf soluble sugar content decreased, but protein carbonylation increased with decreasing Fv/Fm across shade-grown seedlings (L0, LH1, LH2, and LH3) on 19th Oct, suggesting impaired photosynthetic carbon gain and possible membrane peroxidation induced by photooxidative stress, especially in LH2 condition with less N resorption efficiency. Although the impairment of N resorption seems to depend on the timing and intensity of strong light exposure, air temperature, and consequently the degree of photoinhibition, the photoprotective role of anthocyanins in outer-canopy leaves of fullmoon maple might also contribute to allow a safe N resorption in inner-canopy leaves by prolonged shading.

Dual effect of the presence of fruits on leaf gas exchange and water relations of olive trees.

The presence of fruits provokes significant modifications in plant water relations and leaf gas exchange. The underlying processes driving these modifications are still uncertain and likely depend on the water deficit level. Our objective was to explain and track the modification of leaf-water relations by the presence of fruits and water deficit. With this aim, net photosynthesis rate (AN), stomatal conductance (gs), leaf osmotic potential (Ψπ), leaf soluble sugars and daily changes in a variable related to leaf turgor (leaf patch pressure) were measured in olive trees with and without fruits at the same time, under well-watered (WW) and water stress (WS) conditions. Leaf gas exchange was increased by the presence of fruits, this effect being observed mainly in WW trees, likely because under severe water stress, the dominant process is the response of the plant to the water stress and the presence of fruits has less impact on the leaf gas exchange. Ψπ was also higher for WW trees with fruits than for WW trees without fruits. Moreover, leaves from trees without fruits presented higher concentrations of soluble sugars and starch than leaves from trees with fruits for both WW and WS, these differences matching those found in Ψπ. Thus, the sugar accumulation would have had a dual effect because on one hand, it decreased Ψπ, and on the other hand, it would have downregulated AN, and finally gs in WW trees. Interestingly, the modification of Ψπ by the presence of fruits affected turgor in WW trees, the change in which can be identified with leaf turgor sensors. We conclude that plant water relationships and leaf gas exchange are modified by the presence of fruits through their effect on the export of sugars from leaves to fruits. The possibility of automatically identifying the onset of sugar demand by the fruit through the use of sensors, in addition to the water stress produced by soil water deficit and atmosphere drought, could be of great help for fruit orchard management in the future.

Effects of drought stress and plant cultivar type on demographic characteristics of the rose-grain aphid, Metopolophium dirhodum (Hemiptera: Aphididae).

Drought is a substantial threat to cereal production under global climatic change scenarios, albeit its aftermath on arthropod pests is yet contentious. To address this issue, demographic characteristics of Metopolophium dirhodum (Walker, 1849) (Hemiptera: Aphididae) were studied on one drought-susceptible wheat cultivar and one drought-tolerant wheat cultivar under different water treatments. Some physiological and biochemical features of wheat cultivars including leaf soluble sugar and proline contents and antioxidant enzymes activities were also investigated. Significant differences occurred in the developmental period, survival, and fecundity of M. dirhodum between wheat cultivars under various water treatments. The impact of intermediate and severe water stress on M. dirhodum was neutral and negative for the tolerant cultivar and negative for the water-susceptible cultivar, respectively. Under severe water stress, on both wheat cultivars, the aphids had low net reproductive rates and finite and intrinsic rates of increase in comparison with those reared on unstressed plants. In total, drought resulted in lower growth of population and reduced survival of aphids. Hence, in the context of projected climatic changes, acute water deficiency could probably result in reducing the abundance and menace of outburst of M. dirhodum. However, it should be noted that the potential likelihood of M. dirhodum eruptions can be drastically affected by the degree of drought intensity and host plant cultivar.

The effect of abrupt increase in water temperature on the survival and growth of eelgrass Zostera marina

Increased water temperature is considered an important cause of the loss of seagrass beds. This paper quantified the interactive influence of different combinations of water temperature and duration on the responses of Zostera marina plants in terms of survivorship, morphology, growth and physiology. The LT50 (lethal temperature that caused an increase in mortality to 50% of that of the control) and ET50 (effect time that caused a decrease in growth to 50% of that of the control) were calculated to reveal the quantitative relationship between temperature and duration that resulted in limiting effects on the survival and growth of Z. marina plants. Z. marina plants were exposed to different combinations of water temperature [23 (control), 25, 27, 29, and 31 °C] and duration (5, 10, 15 and 20 days), and then the plants were transferred to the control condition for over 30 days under laboratory conditions. The results showed that the survival rate of plants at the end of recovery were significantly lower than those of plants at the end of direct impact under the temperature levels of 29 and 31 °C in each duration, indicating that short-term periods of obviously increased water temperature would lead to long-term effects on the survival of Z. marina plants. Regression analysis revealed that the relationship between water temperature and duration that resulted in limiting effects on the survival and growth of Z. marina could be described as a strong power function. Pearson correlation analysis showed that the survival and growth of Z. marina plants exposed to different temperature levels were significantly correlated with leaf soluble sugar contents. This study will further develop our understanding of the degradation and disappearance of seagrass beds induced by increased temperature.

Response of leaf functional traits to precipitation change: A case study from tropical woody tree

Precipitation change is one of the most important forms of current global climate change, which will significantly influence the plant growth and development. Although numerous experiments have been conducted to investigate the effects of precipitation regulation on the plant growth and ecosystem process, the response of leaf functional traits of tropical woody species to the precipitation change is still poorly understood. In this study, three treatments, including delayed wet season (DW), wetter wet season (WW) and control check (CK), were established to examine the responses of leaf functional traits, including morphological traits, photosynthetic pigments, and non-structural carbohydrates (NSC) of the dominant woody tree, Symplocos chunii , to the simulated precipitation change in a secondary tropical forest of southern China. Our results showed that the specific leaf area (SLA), photosynthetic pigments, and NSC contents exhibited distinctly seasonal variations ( P < 0.05), but the simulated precipitation changes did not alter the leaf morphological traits (leaf length, width, or area) of S. chunii after six-year treatment. The leaf total chlorophyll contents increased observably by 83.9% in DW, and the chlorophyll b was increased by 181.5% compared to CK ( P < 0.05), while WW markedly reduced chlorophyll b content but remarkably increased carotenoid content ( P < 0.05). However, DW significantly reduced NSC contents in both dry and wet seasons. In contract, WW treatment significantly reduced leaf soluble sugar content only in the early stage of wet season, but after that, the WW did not alter the leaf soluble sugar and starch contents, even with the approach of dry season. These indicated that the precipitation change would alter the leaf photosynthetic rates thus influence the carbon assimilation, further regulate the allocation and transformation pattern of leaf NSC contents in tropical woody trees. The results suggest that the tropical woody trees may adapt to the frequent precipitation change via regulating the allocation and transformation of non-structural carbohydrates.

A heat shock transcription factor gene (HaHSFA1) from a desert shrub, Haloxylon ammodendron, elevates salt tolerance in Arabidopsis thaliana

Haloxylon ammodendron is a typical desert xerophyte with worthy genetic resources, therefore, it is necessary to explore the resistance genes of H. ammodendron , and to improve the stress tolerance of other plant species through genetic engineering. In this study, a heat shock transcription factor gene, HaHSFA1 , was firstly cloned from H. ammodendron and overexpressed in Arabidopsis thaliana . The sensitivity of transgenic plants to exogenous ABA, osmotic stress and salt stress were analyzed; the effects of overexpression of HaHSFA1 in Arabidopsis on salt tolerance were deeply investigated. The results indicated that overexpression of HaHSFA1 increased chlorophyll content in Arabidopsis, and the growth of plants was promoted. The leaf soluble sugar and proline contents in OE lines were significantly increased compared with those in WT. OE lines maintained lower osmotic potential and higher shoot water content. Overexpression of HaHSFA1 in Arabidopsis also enhanced antioxidant activity, which may be important for protecting plasma membrane integrity in cells. Overexpression of HaHSFA1 in Arabidopsis improved root activity and increased selective absorption and transport capacity for K + over Na + , which was of great significance to reduce the toxic effect of Na + . This study indicated that overexpression of HaHSFA1 from H. ammodendron significantly elevates the salt tolerance of Arabidopsis, and HaHSFA1 has potential application values in improving abiotic stress tolerance in crops by genetic engineering. • HaHSFA1 was firstly cloned from a desert shrub, Haloxylon ammodendron . • Overexpression of HaHSFA1 enhanced osmotic adjustment and ROS scavenging ability in Arabidopsis. • Overexpression of HaHSFA1 maintained higher selectivity of absorption and transport for K + over Na + in Arabidopsis.