Leaf Net Photosynthetic Rate Research Articles

Potato–Soybean Intercropping Increased Equivalent Tuber Yield by Improving Rhizosphere Soil Quality, Root Growth, and Plant Physiology of Potato

Potato–legume intercropping has been confirmed to increase productivity in modern agricultural systems. However, the physiological and ecological mechanisms of potato–soybean intercropping for promoting tuber yield formation in potato remain unclear. Field experiments were conducted in 2022 and 2023 to explore the responses of tuber yield formation, rhizosphere soil quality, root growth, and plant physiology of potato in potato–soybean intercropping. The soil at the experimental site is Cambisols. The treatments included sole cropping potato, sole cropping soybean, and potato–soybean intercropping. Our results indicated that potato –soybean intercropping decreased the water content, increased the total K content and activities of urease and catalase in rhizosphere soil, and enhanced the root mean diameter, root projected area, and root length density in the 0–5 cm and 15–20 cm soil layers of potato. Moreover, potato–soybean intercropping improved the plant photosynthetically active radiation and light transmittance rate of the middle and lower layers as well as the leaf area index, enhanced the leaf chlorophyll b content and ribulose-1,5-diphosphate carboxylase/oxygenase activity, and increased the leaf net photosynthetic rate and organ dry matter accumulation amounts of potato. The changes in the above parameters resulted in an increased tuber weight per plant (19.4%) and commercial tuber number (42.5%) and then enhanced the equivalent tuber yield of potato (38.2%) and land equivalent ratio (1.31 in 2022 and 1.33 in 2023). Overall, potato–soybean intercropping greatly increased the equivalent tuber yield by improving the rhizosphere soil quality, root growth, and plant physiology of potato and then achieved a higher land equivalent ratio.

Vermicompost application enhances soil health and plant physiological and antioxidant defense to conferring heavy metals tolerance in fragrant rice

Cadmium (Cd) contamination in agricultural soils and its accumulation in plant organs have become a global issue due to its harmful effects on human health. The in-situ stabilizing technique, which involves using organic amendments, is commonly employed for removing Cd from agricultural soils. Thus, the current study investigated the effect of vermicompost (VC) on soil properties and plant physio-biochemical attributes, leaf ultrastructure analysis, antioxidant defense mechanisms, and grain yields of two different fragrant rice cultivars, Xiangyaxiangzhan (XGZ) and Meixiangzhan-2 (MXZ-2), under Cd-stress conditions. The results showed that Cd toxicity deteriorates soil quality, the plant’s photosynthetic apparatus, and the plant’s antioxidant defense mechanism. Moreover, under Cd stress, both cultivars produced significantly lower (p < 0.05) rice grain yields compared to non-Cd stress conditions. However, the VC application alleviated the Cd toxicity and improved soil qualitative traits, such as soil organic carbon, available nitrogen, total nitrogen, phosphorus, and potassium. Similarly, VC amendments improved leaf physiological activity, photosynthetic apparatus function, antioxidant enzyme activities and its related gene expression under Cd stress These enhancements led to increased grain yields of both fragrant under Cd toxicity. The addition of VC mitigated the adverse effects of Cd on the leaf chloroplast structure by reducing Cd uptake and accumulation in tissues. This helped prevent Cd-induced peroxidation damage to leaf membrane lipids by increasing the activities of antioxidant enzymes such as ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD). On average across the growth stages, the Pos-Cd + VC3 treatment increased SOD, APX, CAT, and POD activities by122.2 and 112.5%, 118.6, and 120.6%, 44.6 and 40.6%, and 38.6 and 33.2% in MXZ-2 and XGZ, respectively, compared to the plants treated with Pos-Cd treated alone. Enhancements in leaf physiological activity and plant antioxidant enzyme activity strengthen the plant’s antioxidant defense mechanism against Cd toxicity. In addition, correlation analysis showed a strong relationship between the leaf net photosynthetic rate and soil chemical attributes, suggesting that improved soil fertility enhances leaf physiological activity and boosts rice grain yields. Of the treatments, Pos-Cd + VC3 proved to be the most effective treatment in terms of enhancing soil health and achieving high fragrant rice yields. Thus, the outcomes of this study show that the addition of VC in Cd-contaminated soils could be useful for sustainable rice production and safe utilization of Cd-polluted soil.

Effects of drip irrigation coupled with controlled release potassium fertilizer on maize growth and soil properties

Drip irrigation and the application of controlled-release fertilizers are two effective and important technical measures to conserve water and fertilizer resources and promote the growth and development of maize. However, the underlying physiological mechanism of how drip irrigation combined with controlled release potassium chloride affects maize production and soil properties remains unknown. In different soil water conditions, pot experiments were conducted during the summer maize growing season in 2022 and 2023 to measure maize grain yield, irrigation water productivity, apparent recovery efficiency of potassium, plant physiological characteristics, and soil enzyme activities under the coupling of two irrigation methods (flood irrigation and drip irrigation) and three potassium fertilizer types (potassium chloride (KCl), controlled release potassium chloride (CRK), and 70 % CRK mixed with 30 % KCl). The results revealed that drip irrigation had 6.5–8.1 % and 6.7–9.4 % higher average soil volumetric water content and 3.8–8.1 % and 4.5–13.0 % higher irrigation water productivity than flood irrigation in the two maize growth seasons, respectively. Under the drought conditions, the treatments of 70 % CRK-30 % KCl application led to a significant increase in maize yield by 9.5–10.7 % and 12.2–16.8 % and apparent recovery efficiency of potassium by 8.3–14.2 % and 10.7–10.8 % compared to CRK application treatments in 2022 and 2023, respectively. Compared with the other treatments, the treatment of drip irrigation coupled with 70 % CRK-30 % KCl application under drought conditions (DIDMK) resulted in 4.5–28.7 % and 1.1–31.9 % higher grain yield, 8.2–64.4 % and 8.6–66.8 % higher irrigation water productivity, and 5.9–28.0 % and 6.7–18.9 % higher apparent recovery efficiency of potassium in 2022 and 2023, respectively. Meanwhile, the leaf net photosynthetic rate, rubisco, catalase, peroxidase, and soil enzyme activities of DIDMK treatment were also maintained at a high level. Our results indicated that drip irrigation coupled with 70 % CRK-30 % KCl application were the optimal water and potassium supply modes for maize production. This study can provide useful information regarding summer maize sustainable production and provide theoretical and technical support for summer maize irrigation and potassium fertilizer application technologies in water-scarce regions of China and other similar regions around the world.

Silicon drip fertigation improved sugar beet root and canopy growth and alleviated water deficit stress in arid areas

Crop growth is highly susceptible to drought stress due to water scarcity in arid areas. Silicon (Si) fertilizer could improve the tolerance of crops to drought stress, but the effect of drip fertigation of Si fertilizer on the growth and yield of sugar beets under drought stress is still unclear. In this field experiment conducted in 2022 and 2023 in the arid northwest China, the effects of different Si fertilizer application rates (0 kg ha−1 (Si0), 15 kg ha−1 (Si1), 38 kg ha−1 (Si2), 75 kg ha−1 (Si3)) on the growth, yield, and resource use efficiency of sugar beets (cultivars Beta356 (BT) and Strube13092 (ST)) under deficit irrigation (60 % of crop evapotranspiration (ETc), W2) were explored. The results showed that deficit irrigation (W2Si0) reduced the taproot and fibrous root growth, leaf net photosynthetic rate (Pn), leaf relative water content (LRWC), and leaf area index (LAI) of cultivar BT compared with full irrigation (100 % of ETc, W1). Under deficit irrigation, Si application (W2Si1, W2Si2, and W2Si3) alleviated the drought stress by increasing the number of fibrous roots in 17.5–70.0 cm soil layer and promoted the growth of taproots. Besides, it also increased the leaf moisture and photoassimilate production by increasing plant Si uptake, LRWC, LAI, and Pn. This finally increased the taproot yield (TY), irrigation water use efficiency (IWUE), and partial factor productivity of nitrogen (PFPN) by 11.2 % - 22.9 %, 6.5 % - 19.3 %, and 6.3 % - 19.3 %, respectively in cultivar BT and by 8.8 % - 27.1 %, 13.4 % - 30.8 %, and 13.4 % - 30.8 %, respectively in cultivar ST, compared with W2Si0. Regression analysis showed that the Si fertilizer application rate 64 kg ha−1 could maximize the TY of cultivar BT, but the net revenue (NR) was significantly lower than that of the W1 treatment. The Si fertilizer application rate 71 kg ha−1 could increase the TY of cultivar ST and achieve a NR similar to that of the W1 treatment. Therefore, in arid regions, Si application could alleviate the adverse effects of drought stress on drip-irrigated sugar beet root and shoot growth and improve yield, but the Si application rate varied with sugar beet cultivars.

Seasonal dynamics and punctuated carbon sink reduction suggest photosynthetic capacity of boreal silver birch is reduced by the accumulation of hexose.

The 'assimilates inhibition hypothesis' posits that accumulation of nonstructural carbohydrates (NSCs) in leaves reduces leaf net photosynthetic rate, thus internally regulating photosynthesis. Experimental work provides equivocal support mostly under controlled conditions without identifying a particular NSC as involved in the regulation. We combined 3-yr in situ leaf gas exchange observations (natural dynamics) in the upper crown of mature Betula pendula simultaneously with measurements of concentrations of sucrose, hexoses (glucose and fructose), and starch, and similar measurements during several one-day shoot girdling (perturbation dynamics). Leaf water potential and water and nitrogen content were measured to account for their possible contribution to photosynthesis regulation. Leaf photosynthetic capacity (A/Ci) was temporally negatively correlated with NSC accumulation under both natural and perturbation states. For developed leaves, leaf hexose concentration explained A/Ci variation better than environmental variables (temperature history and daylength); the opposite was observed for developing leaves. The weaker correlations between NSCs and A/Ci in developing leaves may reflect their strong internal sink strength for carbohydrates. By contrast, the strong decline in photosynthetic capacity with NSCs accumulation in mature leaves, observed most clearly with hexose, and even more tightly with its constituents, provides support for the role of assimilates in regulating photosynthesis under natural conditions.

Aeration Alleviated the Adverse Effects of Nitrogen Topdressing Reduction on Tomato Root Vigor, Photosynthetic Performance, and Fruit Development.

To explore the compensation effect of aeration on tomato vegetative and reproductive growth in arid and semi-arid areas, a two-year field experiment was conducted with four micro-nano aeration ratios (0%, 5%, 10%, and 15%) and three nitrogen topdressing levels (80, 60, and 40 kg·ha-1) during the tomato growth period in Ningxia, China. The results showed that increasing the aeration ratio in the range of 0-15% was conducive to the enhancement of tomato root vigor (the ability of triphenyltetrazolium chloride to be reduced, 3-104%) and the leaf net photosynthetic rate (14-63%), favorable to the facilitation of plant dry matter accumulation (3-59%) and plant nitrogen accumulation (2-70%), and beneficial to the improvement of tomato yield (12-44%) and fruit quality. Interestingly, since the aeration ratio exceeded 10%, the increase in the aeration ratio showed no significant effects on the single-fruit weight, tomato yield, and fruit quality. Moreover, with aerated underground drip irrigation, properly reducing the traditional nitrogen topdressing level (80 kg·ha-1) by 25% was favorable for enhancing tomato root vigor (5-31%), increasing tomato yield (0.5-9%), and improving fruit soluble solid accumulation (2-5%) and soluble sugar formation (4-9%). Importantly, increasing the aeration ratio by 5% could compensate for the adverse effects of reducing the nitrogen topdressing level by 25% by improving the leaf photosynthetic rate, promoting plant dry matter accumulation, increasing tomato yield, and enhancing the soluble solid and soluble sugar accumulation in tomato fruits. Synthetically considering the decrease in the nitrogen topdressing amount, leading to plant growth promotion, a tomato yield increase, and fruit quality improvement, a favorable nitrogen topdressing level of 60 kg·ha-1 and the corresponding proper aeration ratio of 10% were suggested for tomato underground drip irrigation in the Yinbei Irrigation District of Ningxia.

Graphene promotes the growth of Vigna angularis by regulating the nitrogen metabolism and photosynthesis.

Graphene has promising applications in agriculture and forestry. In the current study, six different concentrations of graphene (0mg/L, 0.01mg/L, 0.10mg/L, 1.00mg/L, 10.00mg/L, and 100.00mg/L) were used to investigate its effect on the growth and development of V. angularis plants in soil culture. The results showed that the group treated with 1.00mg/L graphene (G-1) had significantly increased plant height (19.86%), stem diameter (24.33%), and leaf area (13.69%), compared to the control group (CK). Moreover, all concentrations of graphene had positive effects on the total root length, total root surface area, and the number of root tips of V. angularis. Compared to the CK group, the G-1 group had significantly increased leaf water potential (37.89%), leaf conductivity (2.25%), and SOD, POD, and CAT activities (47.67%, 35.22%, and 199.3%, respectively). The G-1 group also showed improved leaf net photosynthetic rate, chlorophyll content, and soluble sugar content (51.28%, 24.25%, and 38.35%, respectively), compared to the CK group. Additionally, 1.00mg/L graphene led to a 23.88% increase in the podding rate and a 17.04% increase in the yield of V. angularis plants. The rhizosphere soil of V. angularis treated with 1.00mg/L graphene had a 25.14% increase in hydrolyzable nitrogen content and a 66.67% increase in available phosphorus content. RNA-seq data indicated that 1.00mg/L graphene induced the expression of photosynthesis and nitrogen transmembrane transport genes, including ATP synthase subunit b, photosystem I reaction center subunit XI, photosystem I reaction center subunit IV A, ferredoxin, and psbP-like protein 1, as well as genes for photosynthesis antenna proteins, glutamine synthetase, glutamate dehydrogenase 1, cyanate hydratase, protein fluG-like, and NRT1/PTR family, suggesting that graphene promoted the growth and development of V. angularis by enhancing the photosynthesis and nitrogen metabolism processes in V. angularis plants. Our results indicated that a suitable concentration of graphene could significantly promote the growth of V. angularis plants in soil.

Shading and waterlogging interactions exacerbate summer maize yield losses by reducing assimilate accumulation and remobilization processes

Persistent overcast rain was an essential limiting factor for summer maize production, of which immediate impact was the dual pressure of waterlogging and shading. However, the mechanism of independent and combined effects of waterlogging and shading induced maize yield losses are rarely studied, especially at different growth stages. Denghai 605 (DH605) was selected to be subjected shading, waterlogging, and their combined stress at the 3rd leaf stage (V3), the 6th leaf stage (V6), and tasseling stage (VT). Results showed that shading, waterlogging and their combination significantly limited the expansion of leaf area, and decreased leaf net photosynthetic rate (Pn) and net assimilation rate (NAR), thus reducing the crop growth rate (CGR) and biomass accumulation. At the same time, compared to control, the process of lignin synthesis was inhibited under stressed treatment, resulting in reduced stem mechanical strength and a poor development of the vascular system, of which change significantly reduced efficiency of assimilate remobilization to the ear and ultimately grain yield. The most significant effects of waterlogging and combined stresses on yield were occurred at V3 stage, followed by the V6 and VT stages. The most significant effects of shading were occurred at VT stage, followed by the V6 and V3 stages. Moreover, the compound stress exacerbated the damage brought about by a single stress. It is predicted that climate change will increase the frequency of abiotic stress assemblages, and the results of these findings provide some direction for further research on maize breeding in summer maize under continuous rainy conditions in the future.

Optimizing planting density and nitrogen application to mitigate yield loss and improve grain quality of late-sown wheat under rice-wheat rotation

Late sowing is a critical factor that hinders achieving high-yield, good-quality wheat under rice-wheat rotation. Understanding the physiological basis and regulatory pathways that lead to late-sown wheat of high yield and good quality is crucial for developing effective cultivation strategies. A 2-year field experiment was conducted to investigate the effects of sowing date, nitrogen (N) application rate, and planting density on wheat yield, grain quality, population characteristics, and the underlying physiological factors. The results revealed significant interactions among the sowing date, planting density, and N application in regulating both yield and quality. Late sowing reduced grain yield primarily by reducing the number of spikes and kernels. However, the latter was improved by increasing N application and the planting density, thus mitigating the yield losses caused by late sowing. Moreover, the grain protein content (GPC) and wet gluten content (WGC) increased with delayed sowing dates and higher N rates, but decreased with increased planting densities. For wheat yields over 9,000 or 7,500 kg ha–1, the latest sowing date should not be later than Nov. 4 or 15, respectively. In addition, specific criteria should be met, including a maximum of 1.5 and 1.0 million stems and tillers ha–1, a maximum leaf area index of 6.7 and 5.5, and a dry matter accumulation (DMA) at anthesis of 14,000 and 12,000 kg ha–1, respectively. For high-yield, good-quality late-sown wheat, the optimal combination is a 25% increase in the N rate (300 kg N ha–1) and a planting density of 2.25 million (N300D225) or 3.75 million (N300D375) plants ha–1 for 10- or 20-day delays in sowing, respectively. These combinations result in higher leaf net photosynthetic rate; higher activities of leaf nitrate reductase, glutamine synthetase, and grain glutamic pyruvic transaminase; and a lower sugar-N ratio during post-anthesis.

Root-zone aeration improves fruit yield and quality of tomato by enhancement of leaf photosynthetic performance

Heavy irrigation and soil compaction cause hypoxic stress in plant roots, which limits crop growth. This issue can be solved by root-zone aeration, but the photophysiological responses of crop plants to the dissolved oxygen (DO) concentration in irrigation water remain unclear. Here, a greenhouse plot experiment was conducted to investigate the changes in leaf photosynthesis and plant growth of tomato (Solanum lycopersicum L. cv. ‘Omanda 3′) under aerated irrigation with various DO concentrations. Plants were treated with three different levels of aeration: 5 mg L–1 DO (conventional subsurface irrigation as a non-aeration control), 15 mg L–1 DO (low aeration treatment), and 30 mg L–1 DO (high aeration treatment). Compared with the control, the aeration treatments promoted electron transport from the primary to secondary plastoquinone acceptors (QA to QB) of photosystem II (PSII) and increased leaf net photosynthetic rate in plants at the seedling, fruit expansion, and maturation stages. The opposite effects of aeration treatments were observed at the flowering and fruit-setting stage. The enhancement of leaf photosynthetic performance contributed to improved plant growth, fruit yield, and quality of tomato as a result of increased oxygen supply in the root zone. The aeration treatments additionally facilitated the biosynthesis and transport of photosynthetic carbon assimilates in plant tissues, as evidenced by increased starch and sucrose contents in the leaves and sucrose content in the roots. However, under the high aeration level, excessive transport of sucrose from leaves to roots hindered further improvements in tomato yield and biomass at the maturation stage. Based on plant photophysiological and yield performance, aerated irrigation with a low concentration of DO (15 mg L–1) is recommended for greenhouse tomato crops during the seedling, fruit expansion, and maturation stages, and there is no need of root-zone aeration at the flowering and fruit-setting stage.

Photosynthetic characteristics, yield and quality of sunflower response to deficit irrigation in a cold and arid environment.

In arid regions, deficit irrigation stands as an efficacious strategy for augmenting agricultural water conservation and fostering sustainable crop production. The Hexi Oasis, an irrigation zone situated in Northwest China, serves as a pivotal area to produce grain and cash crops. Nonetheless, due to the predominant conditions of low rainfall and high evaporation, the scarcity of irrigation water has emerged as a critical constraint affecting crop growth and yield in the area. In order to evaluate the effects of deficit irrigation on photosynthetic characteristics, yield, quality, and water use efficiency of sunflower, a two-year field experiment with under-mulched drip irrigation was conducted in the cold and arid environment of the Hexi Oasis region. Water deficits were implemented at sunflower seedling and maturity and consisted of three deficit levels: mild deficit (65-75% field capacity, FC), moderate deficit (55-65% FC), and severe deficit (45-55% FC). A total of six combined water deficit treatments were applied, using full irrigation (75-85% FC) throughout the entire crop-growing season as the control (CK). The results illustrated that water deficit engendered a decrease in leaf net photosynthetic rate, transpiration rate, and stomatal conductance of sunflower compared to CK, with the decrease becoming significant with the water deficit increasing. A mild water deficit, both at the seedling and maturity phases, precipitated a significant enhancement (p< 0.05) in leaf water use efficiency. Under mild water deficit, stomatal limitation emerged as the predominant factor inducing a reduction in the photosynthetic capacity of sunflower leaves, while as the water deficit escalated, non-stomatal limitation progressively assumed dominance. Moreover, a mild/moderate water deficit at seedling and a mild water deficit at maturity (WD1 and WD3) significantly improved sunflower seed quality under consistent yield conditions and significantly increased irrigation water use efficiency, with an average increase of 15.3% and 18.5% over the two years, respectively. Evaluations utilizing principal component analysis and membership function methods revealed that WD1 attained the highest comprehensive score. Consequently, a mild water deficit at both seedling and maturity (WD1) is advocated as the optimal deficit irrigation strategy for sunflower production within the cold and arid environment of Northwest China.

Physiological Response of Tomato and Cucumber Plants to Micro-Spray in High-Temperature Environment: A Scientific and Effective Means of Alleviating Crop Heat Stress

Drought and heat stresses are severe threats to crop production and food security in arid and semi-arid regions of the globe, especially during the summer. This study investigates the effects of micro-spray on micro-climatic and physiological characteristics of cucumber and tomato plants for four growing seasons (two growing seasons each (cucumber: 2017 and 2018 and tomato: 2021 and 2022)). The experiment was conducted in a Venlo-type greenhouse where plants were irrigated with a combined micro-spray and drip irrigation (MSDI) system (1 min for tomato (seven times a day) and 2 mins (four times a day) for cucumber) and drip irrigation (DI). Both plants’ growth and physiological parameters were recorded at the end of the experiment. Moreover, the experimental results showed that plant height and stem diameter increased under MSDI in all seasons. In addition, a micro-spray duration of 2 min decreased the average daily air temperature (Ta) and leaf temperature (T1) by 0.8 °C and 4.9 °C, respectively, and increased the average daily relative humidity (RH) by 4.3%. However, a micro-spray duration of 1 min reduced the average daily Ta and T1 by 0.76 °C and 4.6 °C, respectively, but the increase in RH (2.7%) was much lower than that in the single micro-spray duration of 2 min. In addition, the net leaf photosynthetic rate (Pn), the effective quantum yield of PSII (ΦPSII), and the stomatal conductance (Gs) of both plants increased under MSDI compared with DI. A K-means analysis showed that MSDI could eliminate the adverse effects of sunlight stress on cucumbers and tomatoes. MSDI increased the yield of cucumber and tomato plants by 18.9% and 40.4%, respectively. The fruit weight of cucumber (2017) and tomato (2021) under MSDI did not increase significantly compared to DI, which indicates that MSDI mitigated heat stress, prevented flowers from being burned, and increased the number of fruits. The results also suggested that the total soluble solids in the cucumbers and tomatoes showed no significant differences (p &gt; 0.05) between the two treatments in four seasons. In conclusion, the MSDI system can be an appropriate strategy for the irrigation needs and climate control of plants grown in greenhouses during the hot season.

Effects of slight shading in summer on the leaf senescence and endogenous hormone and polyamine contents in herbaceous peony

Herbaceous peony is a perennial root plant that likes light and is cold-resistant. During summer, high temperature and strong light intensity advance its entry into the leaf wilting stage, which limits the accumulation of nutrients and formation of strong buds and severely affects its growth and development the following year. In this study, the wild herbaceous peony species and two main cultivars, ‘Zifengyu’ and ‘Hongfengyu’, were subjected to slight shading and strong light environments in summer, and their effects on leaf senescence and endogenous hormone and polyamine contents were explored. Slight shading treatment significantly delayed withering, increased the leaf net photosynthetic rate, and increased the chlorophyll, soluble sugar, indole-3-acetic acid, zeatin, gibberellin, spermine, spermidine, putrescine, and polyamine contents. Additionally, slight shading significantly reduced the proline and abscisic acid contents. Slight shading during summer prolonged the green period and delayed leaf senescence. The tolerance of tested materials to strong light intensity in summer was ranked as follows: ‘Zifengyu’ > ‘Hongfengyu’ > wild species. In conclusion, this study revealed that summer leaf senescence is delayed in herbaceous peony through shading and growth regulators. Additional varieties should be evaluated to provide reference for high-efficiency, high-quality, and high-yield cultivation of herbaceous peony.

Rotational strip peanut/cotton intercropping improves agricultural production through modulating plant growth, root exudates, and soil microbial communities

Legume-based intercropping is widely used by smallholder farmers; however, there is scarce information governing the long-term effects of interspecific interactions on the crop growth performance. Here, we present data of 5 years field experimentation on a rotational strip peanut/cotton intercropping system to uncover its beneficial effects on crop production and decipher the underlying mechanisms. Treatments included monoculture of peanut (MP), monoculture of cotton (MC), peanut/cotton intercropping (IC), and peanut/cotton intercropping with solid root barrier (SC). Averaged for 5 years, intercropping did not alter the peanut pods yield whereas the seed cotton yield was significantly increased by 52.63% compared with monoculture. Moreover, the net economic return of IC was significantly increased by 59.49%. Physiological data indicated that the leaf net photosynthetic rate, total biomass, and the accumulation of total nitrogen in peanut pods and cotton buds were significantly increased in IC compared with MP and MC. Meanwhile, the contents of total protein and oleic acid in peanut kernels were also increased by intercropping. Metabolomics evidence showed that differential metabolites from “Tryptophan” and “Carbon” pathways were significantly enriched in peanut and cotton strips of IC. Additionally, IC significantly altered the rhizosphere soil bacterial abundance composition and diversity, and the metabolic functional features of “carbohydrate” and “amino acid” were significantly enriched. Strikingly, the beneficial effects of intercropping were partially counteracted by SC as indicated by the reduction of crop production and net return. Our results demonstrated that rotational strip peanut/cotton intercropping increases production, net economic returns, and peanut quality parameters via the interspecific interactions by enhancing plant growth, regulating root exudates, and modulating soil microbial communities.

Maintenance of xylem hydraulic function during winter in the woody bamboo Phyllostachys propinqua McClure.

Frost is a common environmental stress for temperate plants. Xylem embolism occurs in many overwintering plants due to freeze-thaw cycles, so coping with freeze-thaw-induced embolisms is essential for the survival of temperate plants. This study was conducted on Phyllostachys propinqua McClure, a woody bamboo species that was grown under natural frost conditions to explore its responses to winter embolisms. From autumn to the following spring, the following measurements were recorded: predawn branch and leaf embolism, branch and leaf relative water content (RWC), root pressure and soil temperature, xylem sap osmotic potential, branch and leaf electrolyte leakage (EL), branch nonstructural carbohydrate (NSC) content and leaf net photosynthetic rate. P. propinqua had a mean vessel diameter of 68.95 ±1.27 µm but did not suffer severe winter embolism, peaking around 60% in winter (January), with a distinct reduction in March when root pressure returned. Leaves had a more severe winter embolism, up to 90%. Leaf RWC was much lower in winter, and leaf EL was significantly higher than branch EL in all seasons. Root pressure remained until November when soil temperature reached 9°C, then appeared again in March when soil temperatures increased from -6°C (January) to 11°C. Xylem sap osmotic potential decreased from autumn to winter, reaching a minimum in March, and then increasing again. Soluble sugar (SS) concentration increased throughout the winter, peaked in March, and then decreased. These results suggest that (1) there is a hydraulic segmentation between the stem and leaf, which could prevent stem water loss and further embolization in winter; (2) maintenance of root pressure in early winter played an important role in reducing the effect of freeze-thaw cycles on the winter embolism; (3) the physiological process that resulted in a decrease in xylem sap osmotic potential and tissue water content, and an accumulation of SS associated with cold acclimation also aided in reducing the extent of freeze-thaw-induced embolism. All these strategies could be helpful for the maintenance of xylem hydraulic function of this bamboo species during winter.

Effects of gibberellic acid, kinetin and indole butyric acid mixture on sorghum salinity tolerance and grain yield in saline-alkali coastal zone.

The development and utilization of coastal saline-alkali lands hold significant importance in mitigating the shortage of cultivated land resources in China, enhancing the agro-ecological environment in coastal saline and alkaline areas, and ensuring national food security. We set up both pot and field trials (randomized block design) at Xinxiang experimental station of Institute of Crop Science, Chinese Academy of Agricultural Sciences (ICS-CAAS) and Dongying Yellow River Delta Modern Agricultural Research Base in Shandong Province in 2021 and 2022, respectively. The experimental materials, Jiliang 1 and Jiliang 2, underwent seed dressing with GKI composites at concentrations of 2.5 and 5 mL·kg-1. These composites, which contained the main components of gibberellin, kinetin, and indole butyric acid, were denoted as GKI2.5 and GKI5.0, respectively. The control plots (CK) received water seed dressing. The aim was to assess the regulatory effects of GKI on salt tolerance and grain sorghum yield. Compared to CK, the GKI2.5 and GKI5.0 seed dressing treatments significantly enhanced the growth and development of the two grain sorghum varieties, increased antioxidant enzyme activity and soluble protein content of sorghum leaves, while reducing leaf malondialdehyde content. Moreover, the GKI treatments increased leaf net photosynthetic rate. Under field conditions, yields of Jiliang 1 and Jiliang 2 were enhanced by an average of 17.1% and 19.1%, respectively. In conclusion, GKI seed dressing treatment effectively promoted the growth and development of sorghum under salt stress. It enhanced the antioxidant and osmoregulatory capacities of leaves, reduced the level of membrane lipid peroxidation, and improved net photosynthetic rate of leaves, which together improved the salt tolerance and sorghum yield.

Improving the yield and nitrogen use efficiency of hybrid rice through rational use of controlled-release nitrogen fertilizer and urea topdressing.

Controlled-release fertilizers effectively improve crop yield and nitrogen use efficiency (NUE). However, their use increases the cost of crop production. Optimal management modes involving urea replacement with controlled-release N fertilizers to increase rice yield through enhanced NUE are not widely explored. Field experiments were conducted from 2017 to 2018 to determine the effects of different controlled-release N fertilizers combined with urea [urea-N (180kg ha-1, N1)]. We used controlled-release N (150kg ha-1, N2) as the base, and four controlled-release N and urea-N ratio treatments [(80%:0% (N3), 60%:20% (N4), 40%:40% (N5), or 20%:60% (N6) as the base with 20% urea-N as topdressing at the panicle initiation stage under 150kg ha-1] to study their impact on the grain yield and NUE of machine-transplanted rice. Grain yield and NUE were positively correlated with increases in photosynthetic production, flag leaf net photosynthetic rate (Pn), root activity, N transport, and grain-filling characteristics. The photosynthetic potential and population growth rate from the jointing to the full-heading stage, highly effective leaf area index (LAI) rate and Pn at the full-heading stage, root activity at 15d after the full-heading stage, and N transport in the leaves from the full-heading to mature stage were significantly increased by the N4 treatment, thereby increasing both grain yield and NUE. Furthermore, compared with the other N treatments, the N4 treatment promoted the mean filling rate of inferior grains, which is closely related to increased filled grains per spikelet and filled grains rate. These effects ultimately improved the grain yield (5.03-25.75%), N agronomic efficiency (NAE, 3.96-17.58%), and N partial factor productivity (NPP, 3.98-27.13%) under the N4 treatment. Thus, the N4 treatment with controlled-release N (60%) and urea-N (20%) as a base and urea-N (20%) as topdressing at the panicle-initiation stage proved effective in improving the grain yield and NUE of machine-transplanted hybrid indica rice. These findings offer a theoretical and practical basis for enhancing rice grain yield, NUE, and saving the cost of fertilizer.

Rice Canopy Light Resources Allocation, Leaf Net Photosynthetic Rate, and Yield Formation Characteristics Response to Combined Application of Nitrogen and Potassium

Rice Canopy Light Resources Allocation, Leaf Net Photosynthetic Rate, and Yield Formation Characteristics Response to Combined Application of Nitrogen and Potassium

Response of Leaf Photosynthesis–Transpiration Coupling to Biotic and Abiotic Factors in the Typical Desert Shrub Artemisia ordosica

The environmental regulatory mechanism underlying the coupling of leaf photosynthesis and transpiration in Artemisia ordosica, a typical desert shrub in China, remains unclear. To understand this mechanism, we measured the net leaf photosynthetic rate (Pn), transpiration rate (E), and stomatal conductance (gs) from May to October 2019 using a portable photosynthesis analyser. Photosynthetically active radiation, air temperature, relative humidity, and soil water content were simultaneously measured. Both E and Pn are positively correlated with gs. Pn and E exhibited a nonlinear quadratic correlation from May to July and a linear correlation in August and September. The changes in the maximum photosynthetic (Pn−max) and carboxylation rates were mainly affected by air temperature and light. Seasonally, Pn−max initially exhibited an increasing trend, peaking in June and then decreasing. Under low temperature and light conditions, Pn−E was linearly correlated and the coupling relationship was stable. Under higher temperatures and radiation, Pn−E exhibited a nonlinear quadratic correlation, and decoupling occurred with increasing temperature and light intensity. The results of this study provide a better understanding of the responses of desert shrub ecosystems to climate change.

A study of the soil water potential threshold values to trigger irrigation of ‘Shimizu Hakuto’ peach at pivotal fruit developmental stages

Water management is an important practice that affects fruit size and quality. Effective implementation of irrigation scheduling requires knowledge of the appropriate indicators and thresholds, which are established manly based on the effects of water deficits on final fruit quality. Few studies have focused on the real-time effects of water status on fruit and shoot growth. To establish soil water potential (ψsoil) thresholds to trigger irrigation of peach at pivotal fruit developmental stages, photogrammetry, 13C labelling, and other techniques were used in this study to investigate real-time changes in stem diameter, fruit projected area, net leaf photosynthetic rate (Pn), and allocation of photoassimilates to fruit under soil water potential conditions ranging from saturation to stress in 6-year-old ‘Shimizu hakuto’ peach. Stem growth, fruit growth, and Pn exhibited gradually decreasing sensitivity to water deficits during fruit developmental stages I, II, and III. Stem diameter growth was significantly inhibited when ψsoil dropped to −8.5, −7.6, and −5.4 kPa, respectively. Fruit growth rate was low, reaching zero when the ψsoil was −9.0 to −23.1, −14.9 to −21.4, and −16.5 to −23.3 kPa, respectively, and Pn decreased significantly when the ψsoil reached −24.2, −22.7, and −20.4 kPa, respectively. In addition, more photoassimilates were allocated to fruit under moderate ψsoil conditions (−10.1 to −17.0 kPa) than under other ψsoil values. Our results revealed three ψsoil thresholds, −10.0, −15.0, and −15.0 kPa, suitable for triggering irrigation during stages I, II, and III, respectively. These thresholds can be helpful for controlling excessive tree vigor, maintaining rapid fruit growth and leaf photosynthesis, and promoting the allocation of more photoassimilates to fruit.