Leaf Stomatal Conductance Research Articles

Relationship between submergence of graft union and auxin accumulation of grafted mango trees under flooded conditions

ABSTRACT In recent years, many fields have been affected by floods. In mango trees, grafted trees are more susceptible to flood damage than seedling trees, When the graft union is submerged. In this study, the translocation of substances, especially auxin, through the graft union was investigated to clarify the causes of death in mango trees when the trunk was submerged up to the graft union. After approximately 1 month of flooding, changes were observed in root respiration, carbon dioxide release from the trunk, and leaf stomatal conductance. The auxin content in the scion increased significantly from 19.5 ng g−1 dry weight (DW) in the control to 122.1 ng g−1 (DW) in the flooded treatment. Nevertheless, no significant increase in auxin content was observed in the rootstock. In addition, there was no pectin degradation, leading to the death of the grafted mango trees. Auxin accumulation induces expansins, which are cell wall proteins that loosen the cell wall structure and are involved in structural changes in cell wall polysaccharides. Therefore, submergence of the graft union may inhibit auxin translocation between the scion and rootstock, resulting in pectin degradation in the scion bark and leading to tissue breakdown and death of the mango tree.

The critical role of outside xylem hydraulic conductance in regulating stomatal conductance and water use efficiency in cotton across different planting densities

Hydraulic theory predicts a positive coupling between leaf hydraulic conductance (Kleaf) and stomatal conductance (gs); however, this theory has not been fully supported by observations, and the underlying mechanisms remain unclear. Currently, subdividing Kleaf into leaf hydraulic conductance inside xylem (Kx) and outside xylem (Kox) offers a new perspective for elucidating the regulatory mechanism of Kleaf on gs. Optimal planting density can enhance water use efficiency (WUE) by optimizing gs; however, the changes in leaf hydraulic properties during this process and its regulation of gs and WUE remain unclear. We examined the relationships between Kx and Kox with gs, photosynthetic rate (AN), and WUE, and investigated the structural basis determining Kox in cotton under eight planting densities of 12, 18, 24, 36, 48, 60, 72, and 84 plant m-². The results showed that as the increase of planting density, Kleaf and AN remained consistent while Kox and gs decreased significantly. Kox was significantly influenced by leaf thickness and the volume fraction of inter-cellular air space. Kleaf and Kx showed no correlation with AN or gs, but Kox exhibited a significant positive correlation with gs. Furthermore, Kox is significantly negatively correlated with WUE. These findings suggest that Kox modulates gs to reduce water loss while maintaining AN, thereby enhancing WUE in cotton under various planting densities.

Sensitive Hydraulic and Stomatal Decline in Extreme Drought Tolerant Species of California Ceanothus.

Identifying the physiological mechanisms by which plants are adapted to drought is critical to predict species responses to climate change. We measured the responses of leaf hydraulic and stomatal conductances (Kleaf and gs, respectively) to dehydration, and their association with anatomy, in seven species of California Ceanothus grown in a common garden, including some of the most drought-tolerant species in the semi-arid flora. We tested for matching of maximum hydraulic supply and demand and quantified the role of decline of Kleaf in driving stomatal closure. Across Ceanothus species, maximum Kleaf and gs were negatively correlated, and both Kleaf and gs showed steep declines with decreasing leaf water potential (i.e., a high sensitivity to dehydration). The leaf water potential at 50% decline in gs was linked with a low ratio of maximum hydraulic supply to demand (i.e., maximum Kleaf:gs). This sensitivity of gs, combined with low minimum epidermal conductance and water storage, could contribute to prolonged leaf survival under drought. The specialized anatomy of subg. Cerastes includes trichomous stomatal crypts and pronounced hypodermis, and was associated with higher water use efficiency and water storage. Combining our data with comparative literature of other California species, species of subg. Cerastes show traits associated with greater drought tolerance and reliance on leaf water storage relative to other California species. In addition to drought resistance mechanisms such as mechanical protection and resistance to embolism, drought avoidance mechanisms such as sensitive stomatal closure could contribute importantly to drought tolerance in dry-climate adapted species.

Characterizing the hysteretic effects of water and salinity stresses on root-water-uptake

Characterizing the effects of previous water and salinity stresses is critical for the evaluation of plant water status, which, in turn, is essential for understanding soil-plant water relations and optimizing irrigation schemes. Recent research has found that hysteresis of plant response following water stress alone can be described by an exponential function of the stress degree on the previous day. To explore and quantify the effects of hysteresis concerning salinity stress and combined water-salinity stress, a hydroponic experiment and a soil column experiment on winter wheat, and a field experiment on cotton were conducted. Like water stress, previous salinity stress and combined water-salinity stress also resulted in hysteretic effects on root-water-uptake. Leaf stomatal conductance and plant transpiration rate of stressed crops could only recover gradually from a previous stressed status after re-watering. When stress was mild, compensatory recovery was found, while incomplete recovery occurred when stress was severe. Although the recovery process was closely related to stress history and type, a recovery coefficient was quantified universally with an exponential function of the stress extent on the previous day (with a coefficient of determination R2 ≥ 0.60). Consideration of hysteresis for water and salinity stresses with a mathematical model led to significant improvement in the simulation of both relative transpiration rate (R2 = 0.94, root mean squared error RMSE = 0.04, maximal absolute error MAE = 0.12) and soil water content (R2 = 0.90, RMSE = 0.01 cm3 cm–3, MAE = 0.03 cm3 cm–3), especially during the recovery periods severely affected by historical stress. Consideration of hysteresis is expected to benefit regulation of soil water and salinity and thus enhance water use efficiency. However, the mechanisms underlying hysteresis, especially the compensatory recovery mechanisms, still need to be further investigated.

Physiological Behavior of Rubber Plants (<i>Hevea Brasilliensis</i>) to Different Soil Moisture Conditions

Drought conditions can severely impact rubber (<i>Hevea brasiliensis</i>) plantations, leading to economic loss in Malaysia. The study aimed to assess the impact of varying soil moisture levels on the physiological characteristics of five latex timber clones (LTCs) of rubber, with the goal of identifying the most suitable clone for specific soil moisture conditions. These conditions include (1) field capacity, (2) 75% available water (AW), (3) 50% AW, (4) 25% AW, and (5) wilting point, with the ultimate objective of optimizing cultivation methods and fostering sustainable rubber production in Malaysia. The five clones under investigation include RRIM3001, RRIM2025, RRIM2001, RRIM928, and PB350. Leaf chlorophyll content, stomatal conductance, and net photosynthesis were measured 4 and 8 months after treatment (MAT). The findings indicated significant effects of moisture stress on various physiological attributes, including total chlorophyll content, relative chlorophyll content, stomatal conductance, and net photosynthesis rate. At 4 and 8 MATs, the clones subjected to field capacity exhibited the highest values for these physiological characteristics, followed by those exposed to 75% available water, with the lowest values observed at the wilting point. RRIM3001 consistently exhibited the highest total chlorophyll content, stomatal conductance, and net photosynthesis among the clones at both sampling dates. The highest net photosynthesis was observed in the RRIM3001 clone under field capacity conditions. Furthermore, a significant positive correlation was identified between total chlorophyll and relative chlorophyll contents, as well as between net photosynthesis and stomatal conductance. These findings carry practical implications for water management during the initial growth phase of rubber seedlings and for replanting initiatives in rubber plantations.

Unirrigated extensive green roofs in humid subtropics – Plant selection and substrate design for low maintenance and climate resilience

Low-maintenance extensive green roofs hold the potential for adapting to climate change, but there is a limited understanding of their effective design in humid subtropical regions. In this study, we aimed to investigate low-maintenance green roof ecosystems capable of thriving under heat stress. Plant growth performance was evaluated in the second year of an experimental green roof in southwest China. This green roof was unirrigated and involved two plant communities (forbs and grasses) cultivated in four substrate types. Metrics of growth performance, including plant survival, green coverage, visual appearance, leaf stomatal conductance, and substrate volumetric water content were used to analyze the impact of substrate on plant growth. ESP substrate, comprising 30 %v (percent of volume) expanded shale, 25 %v perlite, 25 %v vermiculite, and 20 %v compost, featured the highest porosity and optimal growth of forbs, achieving an average green coverage of 66.76 % and average visual appearance value of 3.56 throughout the monitoring period. The high total porosity of this substrate could be critical in facilitating root development and drainage. Moreover, during the summer’s heat and drought, while substrate water content is not a limiting factor for the survival of some established forbs, it remains crucial for the growth of grasses. Additionally, the same substrate impacts different plant communities variably. Four particularly well-performing forb species, namely Lycoris chinensis, Tradescantia pallida, Liriope muscari, and Salvia farinacea, demonstrated survival rates closed to 100 % and an average visual appearance value exceeding 3 was noted, and thus, they are recommended as plant candidates for unirrigated green roofs. The distinguished performance of these species is attributable to their adaptation to heat and drought through specific physiological traits. Our findings provide insights into vegetation selection and substrate optimization for the successful establishment of extensive green roofs that could be feasibly developed without irrigation in the humid subtropical regions.

AtZAT10/STZ1 improves drought tolerance and increases fiber yield in cotton.

Drought poses a significant challenge to global crop productivity, necessitating innovative approaches to bolster plant resilience. Leveraging transgenic technology to bolster drought tolerance in crops emerges as a promising strategy for addressing the demands of a rapidly growing global populace. AtZAT10/STZ1, a C2H2-type zinc finger protein transcription factor has shown to significantly improve Arabidopsis' tolerance to various abiotic stresses. In this study, we reports that AtSTZ1 confers notable drought resistance in upland cotton (Gossypium hirsutum), amplifying cotton fiber yield under varying conditions, including irrigated and water-limited environments, in field trials. Notably, AtSTZ1-overexpressing transgenic cotton showcases enhanced drought resilience across critical growth stages, including seed germination, seedling establishment, and reproductive phases. Morphological analysis reveals an expanded root system characterized by an elongated taproot system, increased lateral roots, augmented root biomass, and enlarged cell dimensions from transgenic cotton plants. Additionally, higher contents of proline, chlorophyll, soluble sugars, and enhanced ROS-scavenging enzyme activities are observed in leaves of transgenic plants subjected to drought, underscoring improved physiological adaptations. Furthermore, transgenic lines exhibit heightened photosynthetic rate, increased water use efficiency, and larger stomatal and epidermal cell sizes, coupled with a decline in leaf stomatal conductance and density, as well as diminished transpiration rates compared to the wild type counterparts. Transcriptome profiling unveils 106 differentially expressed genes in transgenic cotton leaves post-drought treatment, including protein kinases, transcription factors, aquaporins, and heat shock proteins, indicative of an orchestrated stress response. Collectively, these findings underscore the capacity of AtSTZ1 to augment the expression of abiotic stress-related genes in cotton following drought conditions, thus presenting a compelling candidate for genetic manipulation aimed at enhancing crop resilience.

Photosynthetic Traits of Quercus coccifera Green Fruits: A Comparison with Corresponding Leaves during Mediterranean Summer

Fruit photosynthesis occurs in an internal microenvironment seldom encountered by a leaf (hypoxic and extremely CO2-enriched) due to its metabolic and anatomical features. In this study, the anatomical and photosynthetic traits of fully exposed green fruits of Quercus coccifera L. were assessed during the period of fruit production (summer) and compared to their leaf counterparts. Our results indicate that leaf photosynthesis, transpiration and stomatal conductance drastically reduced during the summer drought, while they recovered significantly after the autumnal rainfalls. In acorns, gas exchange with the surrounding atmosphere is hindered by the complete absence of stomata; hence, credible CO2 uptake measurements could not be applied in the field. The linear electron transport rates (ETRs) in ambient air were similar in intact leaves and pericarps (i.e., when the physiological internal atmosphere of each tissue is maintained), while the leaf NPQ was significantly higher, indicating enhanced needs for harmless energy dissipation. The ETR measurements performed on leaf and pericarp discs at different CO2/O2 partial pressures in the supplied air mixture revealed that pericarps displayed significantly lower values at ambient gas levels, yet they increased by ~45% under high CO2/O2 ratios (i.e., at gas concentrations simulating the fruit’s interior). Concomitantly, NPQ declined gradually in both tissues as the CO2/O2 ratio increased, yet the decrease was more pronounced in pericarps. Furthermore, net CO2 assimilation rates for both leaf and pericarp segments were low in ambient air and increased almost equally at high CO2, while pericarps exhibited significantly higher respiration. It is suggested that during summer, when leaves suffer from photoinhibition, acorns could contribute to the overall carbon balance, through the re-assimilation of respiratory CO2, thereby reducing the reproductive cost.

Research on the Mechanism of Growth of Codonopsis pilosula (Franch.) Nannf. Root Responding to Phenolic Stress Induced by Benzoic Acid.

Soil autotoxic chemosensory substances have emerged as the predominant environmental factors constraining the growth, quality, and yield of Codonopsis pilosula in recent years. Among a vast array of chemosensory substances, benzoic acid constitutes the principal chemosensory substance in the successive cultivation of C. pilosula. However, the exploration regarding the stress exerted by benzoic acid on the growth and development of C. pilosula remains indistinct, and there is a scarcity of research on the mechanism of lobetyolin synthesis in C. pilosula. In the current research, it was discovered that exposure to benzoic acid at a concentration of 200 mmol/L conspicuously attenuated the plant height, root length, total length, fresh weight, root weight, root thickness, chlorophyll content, electrolyte osmolality, leaf intercellular CO2 concentration (Ci), net photosynthesis rate (Pn), transpiration rate (Tr), and leaf stomatal conductance (Gs) of C. pilosula. Benzoic acid (200 mmol/L) significantly enhanced the activity of root enzymes, including superoxide dismutase (SOD), malondialdehyde (MDA), and peroxidase (POD), as well as the accumulation of polysaccharides and lobetyolins (polyacetylene glycosides) in the roots of C. pilosula. In this study, 58,563 genes were assembled, and 7946 differentially expressed genes were discovered, including 4068 upregulated genes and 3878 downregulated genes. The outcomes of the histological examination demonstrated that benzoic acid stress augmented the upregulation of genes encoding key enzymes implicated in the citric acid cycle, fatty acid metabolism, as well as starch and sucrose metabolic pathways. The results of this investigation indicated that a moderate amount of benzoic acid could enhance the content of lobetyolin in C. pilosula and upregulate the expression of key coding genes within the signaling cascade to improve the resilience of C. pilosula lobetyolin against benzoic acid stress; this furnished a novel perspective for the study of C. pilosula lobetyolin as a potential substance for alleviating benzoic acid-induced stress.

Shading Impairs Mycorrhizal Benefits on Plant Growth, Leaf Gas Exchange, and Active Ingredients in Polygonum cuspidatum

Polygonum cuspidatum, an important medicinal plant, often experiences shading from surrounding vegetation during its growth phase, raising questions about the impact of such conditions on the functionality of arbuscular mycorrhizal fungi. This study investigated the effects of an arbuscular mycorrhizal fungus (Funneliformis mosseae) on the growth, leaf gas exchange, and concentrations of active ingredient concentrations in leaves and roots of P. cuspidatum under shading (with a 72% shading rate) conditions. A nine-week shading intervention significantly suppressed root colonization by F. mosseae and the formation of soil mycorrhizal mycelium. Shading significantly inhibited the above-ground growth performance, biomass production, leaf photosynthetic rate, transpiration rate, stomatal conductance, and intercellular CO2 concentration, while F. mosseae significantly increased these variables in the absence of shading. Plant height, leaf biomass, stem biomass, leaf photosynthetic rate, transpiration rate, and stomatal conductance were all decreased by F. mosseae when the plants were shaded. The shading treatment also significantly diminished the concentrations of active components measured in both leaves and roots. Under no-shading conditions, F. mosseae significantly boosted the concentrations of polydatin, resveratrol, aloe-emodin, emodin, chrysophanol, and physcion in roots, as well as the concentrations of polydatin and chrysophanol in leaves. Conversely, in the presence of shading, F. mosseae distinctly reduced these active ingredient levels in roots, followed by an increase in leaf polydatin and chrysophanol concentrations. In summary, shading substantially impaired the mycorrhizal benefits on plant growth, leaf gas exchange, and root active ingredients in P. cuspidatum, highlighting the importance of sufficient light to maximize mycorrhizal contributions.

Arbuscular mycorrhizal fungus activates wheat physiology for higher reproductive allocation under drought stress in primitive and modern wheat

Arbuscular mycorrhizal fungus (AMF) can mediate physiological adaptation of higher plants to drought stress, including wheat. Yet, it is unclear how AMF affects reproductive output via mediating crop physiological vitality at the evolutionary scale. To clarify this issue, a growth environment-controlled experiment was conducted using four primitive wheat genotypes and four modern ones with or without AMF (Funneliformis mosseae) inoculation. Two water regimes (80 % and 40 % field water capacity, FWC80 (well-watered) and FWC40 (drought stress)) were included. The data indicated that AMF inoculation significantly improved leaf area, photosynthetic rate, stomatal conductance and water use efficiency under drought stress, compared to the non-AMF group (CK). Regardless of soil moisture, the relationship between reproductive biomass vs. vegetative biomass (R-V), and between leaf biomass vs. shoot biomass, all fell into a typical allometric pattern (α>1, P<0.001) in primitive wheat. In contrast, in modern wheat, the R-V relationship tended to an isometric pattern (α≈1, P<0.001), showing lower α values in all treatments relative to primitive ones. Furthermore, AMF inoculation significantly promoted the maintenance rate of yield and biomass under drought stress, suggesting greater drought tolerance as induced by AMF in modern wheat compared to primitive ones. These findings illuminated a key evolutionary strategy to enhance reproductive allocation via activating physiological activities under drought stress from primitive to modern wheat.

Purslane (Portulaca oleracea L.) Growth, Nutritional, and Antioxidant Status under Different Nitrogen Levels in Hydroponics

Purslane (Portulaca oleracea L.) is a common weed that attracts research and agricultural attention because of its significant nutritional value, and it is used commercially. The present work rated the effect of different nitrogen (N) concentrations, i.e., N50: 50 mg L−1; N100: 100 mg L−1; N200: 200 mg L−1; and N300: 300 mg L−1, on the growth, physiology, antioxidant capacity, and nutrient accumulation in the different plant parts of hydroponically grown purslane. Seedlings were transplanted to a Nutrient Film Technique (NFT) system and exposed to different N levels. The plants grown in high N levels of 300 mg L−1 had decreased biomass production, leaf number, leaf stomatal conductance, and total flavonoid content because of the increased oxidative stress, as shown by the elevated lipid peroxidation levels. Several enzymatic (superoxide dismutase) and non-enzymatic (ascorbic acid, total phenolics) plant antioxidant activities were activated to counteract the oxidative factors. Plants grown in intermediate N levels in the NS (i.e., 100 mg L−1) had decreased oxidative stress as several enzymatic antioxidant activities, i.e., peroxidases and catalases, were increased. Additionally, the water use efficiency and nitrogen uptake, as well as leaf stomatal conductance and leaf chlorophyll fluorescence, were increased in plants grown at a N level of 200 mg L−1. The mineral accumulation in the leaves, stems, and roots fluctuated, with increased calcium, magnesium, and sodium content being observed in the plants grown at high N levels in the nutrient solution. The stems accumulated less N compared with the leaves, but the N content and accumulation rates in purslane leaves were not affected by the N levels in the nutrient solution. Therefore, to increase the yield, nutritional value, and water use efficiency of purslane that is grown hydroponically, a concentration of 200 mg L−1 N in the nutrient solution is recommended.

The Influence of Microalgae Fertilizer on Soil Water Conservation and Soil Improvement: Yield and Quality of Potted Tomatoes

We aim to study the impact of microalgae fertilizer on soil nutrients, water conservation and crop yield and quality while also determining the optimal ratio of microalgae fertilizer to chemical fertilizer. Using “Xinoufen No.9” tomatoes as the test subject, we conducted pot experiments with four different treatments: control with 100% chemical fertilizer (CK), T1 (25% microalgae fertilizer + 75% regular chemical fertilizer), T2 (75% microalgae fertilizer + 25% regular chemical fertilizer) and T3 (100% microalgae fertilizer). The results show that an increased application of microalgae fertilizer enhanced the soil organic matter, ammonium nitrogen, available phosphorus and potassium content. T3 showed the most improvement followed by T2. The co-application of microalgae fertilizer with chemical fertilizer can significantly increase the stem girth, plant height and yield of tomatoes. At the same time, microalgae fertilizer effectively regulates leaf stomatal conductance, promoting tomato leaf respiration. As the stomatal conductance increases, the transpiration rate and net photosynthesis rate of all treatments improve, followed by a decline in intercellular CO2 concentration, with T2 exhibiting the best performance. Among all treatments, T2 treatment yielded the highest per-plant production (0.630 kg), followed by T3 (0.521 kg). This is because the microalgae fertilizer promotes the distribution of photosynthetic products to the fruit, enhancing the yield and quality of tomatoes. Additionally, the microalgae fertilizer also increases the content of soluble sugars, soluble protein, vitamin C and lycopene in the fruit while reducing the nitrate content. Compared to the control group CK, T2 increases the content of soluble sugars, vitamins and lycopene by 26.74%, 39.29% and 158.31%, respectively. Microalgae fertilizer also helps to improve soil water and thermal conditions, enhancing the water-use efficiency of tomatoes. Compared to CK, the water-use efficiency of T2 treatment increased by 54.05%. Correlation analysis indicates that water and fertilizer factors significantly affect tomato yield, with a correlation exceeding 70%. The net photosynthesis and transpiration rates significantly influence fruit quality, with correlations above 80%. By applying microalgae fertilizer, the efficiency of water and fertilizer use can be effectively improved, thus achieving the goal of water conservation and quality enhancement. Therefore, through comprehensive analysis, using the membership function method of indicators such as soil environment, crop yield, fruit quality and water-use efficiency, it is concluded that T2 is the optimal fertilization treatment. This study provides theoretical support for the application of microalgae biofertilizer technology in the cultivation of tomatoes and other vegetables in the northern, cold and arid regions.

Carboxylation capacity is the main limitation of carbon assimilation in High Arctic shrubs.

Increases in shrub height, biomass and canopy cover are key whole-plant features of warming-induced vegetation change in tundra. We investigated leaf functional traits underlying photosynthetic capacity of Arctic shrub species, particularly its main limiting processes such as mesophyll conductance. In this nutrient-limited ecosystem, we expect leaf nitrogen concentration to be the main limiting factor for photosynthesis. We measured the net photosynthetic rate at saturated light (Asat) in three Salix species throughout a glacial valley in High-Arctic tundra and used a causal approach to test relationships between leaf stomatal and mesophyll conductances (gsc, gm), carboxylation capacity (Vcmax), nitrogen and phosphorus concentration (Narea, Parea) and leaf mass ratio (LMA). Arctic Salix species showed no difference in Asat compared to a global data set, while being characterized by higher Narea, Parea and LMA. Vcmax, gsc and gm independently increased Asat, with Vcmax as its main limitation. We highlighted a nitrogen-influenced pathway for increasing photosynthesis in the two prostrate mesic habitat species. In contrast, the erect wetland habitat Salix richardsonii mainly increased Asat with increasing gsc. Overall, our study revealed high photosynthetic capacities of Arctic Salix species but contrasting regulatory pathways that may influence shrub ability to respond to environmental changes in High Arctic tundra.

Photosynthetic Response to Phosphorus Fertilization in Drought-Stressed Common Beech and Sessile Oak from Different Provenances.

Increasingly frequent and severe droughts pose significant threats to forest ecosystems, particularly affecting photosynthesis, a crucial physiological process for plant growth and biomass production. This study investigates the impact of phosphorus fertilization on the photosynthesis of common beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Liebl.). In a common garden experiment, saplings originating from two provenances (wetter KA and drier SB provenances) were exposed to regular watering and drought in interaction with moderate and high phosphorus concentrations in the growing substrate. Results indicated that drought significantly reduced pre-dawn leaf water potential (ΨPD), net photosynthesis (Anet), stomatal conductance (gs) and photosynthetic performance index (PIabs) in both species. Phosphorus fertilization had a negative impact on Anet and PIabs, thus exacerbating the negative impact of drought on photosynthetic efficiency, potentially due to excessive phosphorus absorption by saplings. Provenance differences were notable, with the KA provenance showing better drought resilience. This research highlights the complexity of nutrient-drought interactions and underscores the need for cautious application of fertilization strategies in reforestation efforts under changing climatic conditions.

Leaf Area Influences Photosynthetic Activities, Raisin Yield and Quality in Manjari Kishmish Grape Variety

The ideal leaf area is essential for optimizing photosynthesis and resource distribution, which improves both yield and quality. Leaf retention is a cultural practice that involves maintaining definite number of leaves above the bunch to optimize photosynthetic efficiency and fruit quality. The experiment was conducted at the ICAR-National Research Centre for Grapes with different treatments of number of leaves above the bunch (10, 12, 14, 16 and &gt;16 leaves). The parameters measured included leaf area, photosynthetic rate, stomatal conductance, transpiration rate, bunch weight, berry quality and raisin recovery. The results revealed that retaining 14 leaves above bunch with leaf area of 1066.33 cm2 resulted in maximum bunch weight (365.00 g), 50-berry weight (123.31 g), yield/vine (23.72 kg) and raisin recovery (26.54 %) while, minimum bunch weight (300.00 g), 50-berry weight (103.48 g), yield/vine (19.20 kg) and raisin recovery (24.35 %) were observed in more than16 leaves above the bunch. However, the leaf area/shoot (2888.00 cm2), leaf area/vine (69312.00 cm2), leaf area/bunch (1066.33 cm2) and leaf area/g berry weight (2.92 cm2/g) were found sufficient for high quality grape and raisin production in a vine spaced at 9 X 5 feet distance which was achieved through 14 leaves above the bunch in Manjari Kishmish grape. It is therefore recommended to maintain approximately 14 leaves above the bunch in Manjari Kishmish that will help to maximize photosynthetic efficiency, enhance leaf area distribution and support higher yield, raisin and better berry quality.

Effects of different water stresses under subsurface infiltration irrigation on eggplant growth and water productivity

Soil moisture deficiency limits eggplant growth and affects the yield and quality. Identifying an appropriate deficit irrigation strategy to enhance irrigation water productivity is an urgent task. Additionally, the dynamic response of eggplants to water stress at various phenological stages needs further clarification. In this study, eggplants were used as experimental materials, with field capacity (FC) (Senyigit et al.) serving as the irrigation standard. Two levels of deficit irrigation treatments (60 % FC and 50 % FC) were applied at three key phenological stages of eggplant (seedling stage, flowering and fruiting, and prime fruit stage). A randomized block design was used with non-deficit irrigation (80 % FC) during the phenological stages as the control (W1), resulting in seven treatments, each with three replicates. The results showed that at the same phenological stage, plant height, stem diameter, leaf area index (LAI), dry matter accumulation, total fresh root weight, total root length, total root surface area, and total root volume decreased as the irrigation threshold was lowered. The content of vitamin C, soluble sugars, souble proteins, and crude fiber increased as the irrigation threshold decreased. Leaf photosynthetic parameters (photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO2 concentration (Ci)) were positively correlated with the irrigation threshold. The W1 treatment had the highest yield (89.1 t·ha−1 in 2018; 88.8 t·ha−1 in 2019), followed by the W2 treatment (86.1 t·ha−1 in 2018; 85.6 t·ha−1 in 2019). Water deficit during the prime fruit stage (W6, W7) had the most significant impact on yield. W1 had the highest water productivity (19.4 kg·m−3 in 2018; 19.2 kg·m−3 in 2019), with no significant difference from W2 (19.4 kg·m−3 in 2018; 19.0 kg·m−3 in 2019). Using the Jensen function, the water sensitivity of eggplants at different phenological stages was ranked as follows:prime fruit stage > flowering and fruiting stage > seedling stage. Path analysis indicated that dry matter accumulation, single fruit weight, and single plant yield were important indicators affecting yield. Considering irrigation amount, eggplant growth, fruit yield and quality, and water productivity, the optimal deficit irrigation thresholds for eggplants in arid regions are determined to be 60 % FC during the seedling stage, 60 % FC during the flowering and fruiting stage, and 80 % FC during the prime fruit stage. The findings of this study offer valuable insights for precision agricultural irrigation practices.

Waterlogging‐Induced Changes in ABA, Carbohydrates and CBF6 Modify Freezing Tolerance in Prehardened Festuca pratensis

ABSTRACTChanges in precipitation and snow melt during warmer winters can increase low‐temperature waterlogging. Such conditions may bring about different effects when compared with a single stress trigger, such as low‐temperature or water excess. The effects of waterlogging are clearly related to water temperature, and the consequences of water excess might be less severe, as more oxygen is dissolved in colder water. The effect of waterlogging during cold acclimation (CA) is poorly understood; most experiments concerning water excess are performed at relatively high‐temperatures. In this study, we examined the effect of 3 weeks of waterlogging (approx. 2 cm above the soil level) on CA in Festuca pratensis Huds. (Fp), a cool‐season grass. Measurements were taken before CA (after prehardening, before flooding) and after 3 weeks of CA in waterlogged (treated) and non‐waterlogged (control) plants. The work included: (i) freezing tolerance test (regrowth after freezing), (ii) analysis of abscisic acid (ABA) content in the leaf, (iii) leaf stomatal conductance, (iv) leaf water content, (v) carbohydrates analysis, including fructans, and (vi) transcript levels of selected genes involved in freezing tolerance, ABA signalling and fructan biosynthesis. The aim of the study was to test a hypothesis that low‐temperature waterlogging in Fp enhances freezing tolerance (plant regrowth after freezing) related to increased ABA accumulation, increased C‐repeat‐binding transcription factor expression and/or increased carbohydrate accumulation, including fructans. Two out of four genotypes exhibited enhanced regrowth following freezing due to waterlogging relative to control. Principal component analysis (PCA) revealed a positive correlation between ABA levels and freezing tolerance in both treatments, with a more pronounced effect observed in the waterlogged plants. However, the phytohormone played different roles in these two treatments. In the context of low‐temperature waterlogging, ABA may be involved in the dehydration tolerance response in genotypes suffering from physiological drought, as well as the induction of C‐repeat‐binding transcription factors (CBFs) and sucrose, which may improve freezing tolerance. The increased fructan amount and polymerisation degree due to waterlogging may provide a carbohydrate sink to maintain a high photosynthetic efficiency, but are not directly responsible for freezing tolerance changes. The study indicates that tolerance mechanisms of Fp exposed to low‐temperature waterlogging involve maintaining a high photosynthetic rate, as well as oxidative and dehydration stress tolerance.

Effect of Green Light Replacing Some Red and Blue Light on Cucumis melo under Drought Stress.

Light quality not only directly affects the photosynthesis of green plants but also plays an important role in regulating the development and movement of leaf stomata, which is one of the key links for plants to be able to carry out normal growth and photosynthesis. By sensing changes in the light environment, plants actively regulate the expansion pressure of defense cells to change stomatal morphology and regulate the rate of CO2 and water vapor exchange inside and outside the leaf. In this study, Cucumis melo was used as a test material to investigate the mitigation effect of different red, blue, and green light treatments on short-term drought and to analyze its drought-resistant mechanism through transcriptome and metabolome analysis, so as to provide theoretical references for the regulation of stomata in the light environment to improve the water use efficiency. The results of the experiment showed that after 9 days of drought treatment, increasing the percentage of green light in the light quality significantly increased the plant height and fresh weight of the treatment compared to the control (no green light added). The addition of green light resulted in a decrease in leaf stomatal conductance and a decrease in reactive oxygen species (ROS) content, malondialdehyde MDA content, and electrolyte osmolality in the leaves of melon seedlings. It indicated that the addition of green light promoted drought tolerance in melon seedlings. Transcriptome and metabolome measurements of the control group (CK) and the addition of green light treatment (T3) showed that the addition of green light treatment not only effectively regulated the synthesis of abscisic acid (ABA) but also significantly regulated the hormonal pathway in the hormones such as jasmonic acid (JA) and salicylic acid (SA). This study provides a new idea to improve plant drought resistance through light quality regulation.

Ecosystem-scale carbon dynamics in desert Shrublands: Unraveling the complex interplay among leaf functional and physiological traits and environment

Understanding the relationships and dynamics of environmental variables, leaf traits, and photosynthetic parameters in determining gross ecosystem productivity (GEP) is fundamental to assessing the carbon (C) cycle. However, existing knowledge in this area, especially concerning desert ecosystems, remains entirely inadequate. In this study, we used near-continuous eddy covariance, foliar, and photosynthetic data acquired from an Artemisia ordosica-dominated shrubland over a seven-year period (2013–2019). The study proceeded to assess: (i) the influence of environmental variables on GEP as a function of leaf phenology, (ii) the role of foliar traits and photosynthetic parameters in regulating GEP, and (iii) resource use strategies adopted by A. ordosica in response to adverse environmental conditions. Analysis of controlling factors indicated that various environmental and photo-physiological factors influenced GEP to different extents, depending on leaf phenology. During the leaf-expanding phase, GEP was largely controlled by maximum carboxylation rate (Vcmax). With leaf expansion, the leaf dark respiration rate (Rd), stomatal conductance (Gs), and light compensation point (LCP) played pivotal roles in an upregulation of GEP. However, during the leaf-coloring phase, GEP was limited by the maximum electron transport rate (Jmax). Our findings accentuate A. ordosica's conservative strategy in nitrogen resource investment, which influences the shrubland's role as a C sink. These insights emphasize the importance of considering both climatic and plant physiological controls, especially as it pertains to photosynthesis, when seeking to understand broader C dynamics in desert ecosystems.