Photosynthesis Characteristics Research Articles

Unlocking the Potential of Pepper Plants under Salt Stress: Mycorrhizal Effects on Physiological Parameters Related to Plant Growth and Gas Exchange across Tolerant and Sensitive Genotypes.

Agriculture is confronted with the challenge of ensuring global food security, yet the rapid expansion of salinity stress undoubtedly restricts plant productivity in cultivable areas, posing a significant threat to crop yields. Arbuscular mycorrhizal fungi (AMFs) have emerged as a biological tool for enhancing plant salt stress tolerance. To utilize this biological tool, this study evaluated the response in growth and physiological parameters of tolerant (Karaisali) and sensitive (Demre) pepper genotypes. The experiment involved mycorrhizal-treated (Glomus clarium) and non-mycorrhizal (control) plants of both the tolerant and sensitive pepper genotypes. The plants were subjected to two salt doses: 75 and 150 mM. The plant growth and physiological parameters were measured at 40 days after transplanting. The mycorrhizal activity was found to be significantly more effective in the sensitive genotype. We found notable differences in mycorrhizal activity between the pepper genotypes under salt stress conditions, with the sensitive genotype "Demre" showing greater responsiveness to mycorrhizal association compared with the "Karaisali" variety. Under both moderate (75 mM NaCl) and higher salt stress levels (150 mM NaCl), both the "Karaisali" and "Demre" varieties exhibited substantial increases in their shoot dry weights. However, these increases were consistently higher in the "Demre" plants. Moreover, the AMFs demonstrated significant enhancements in photosynthesis rates under both moderate and high salinity levels in both genotypes. Overall, our findings suggest that AMFs play a crucial role in improving plant growth, water status, and photosynthesis characteristics, particularly in salt-sensitive pepper genotypes, under moderate-to-high salinity levels. In conclusion, the plant growth, water status, and photosynthesis characteristics of the salt-sensitive pepper genotype were significantly improved by AMFs at medium and high salinity levels, such as 75 mM and 150 mM NaCl, respectively.

Appropriate Nitrogen Application for Alleviation of Soil Moisture-Driven Growth Inhibition of Okra (Abelmoschus esculentus L. (Moench))

Uneven rainfall, in the context of global warming, can cause soil moisture fluctuations (SMFs) that harm crop growth, and it is not yet known whether nitrogen (N) can mitigate the harm caused by a strong SMF. This paper uses okra as a test subject and sets three SMFs of 45–55% FC (W1), 35–65% FC (W2), and 25–75% FC (W3) and three N applications of 0 kg hm−2 (N0), 110 kg hm−2 (N1), and 330 kg hm−2 (N2) to investigate the effects of SMF and N application on the physiological and biochemical aspects of okra. The results demonstrated that okra exhibited the highest values in stem diameter, number of leaves, photosynthesis characteristics, antioxidant enzyme activity, and yield under the N1 treatment. The average yield in the N1 treatment was 149.8 g, significantly surpassing the average yields of the N0 (129.8 g) and N3 (84.0 g) treatments. Stomatal density, antioxidant enzyme activity, malondialdehyde content, and proline content in okra leaves were highest in the W3 treatment, indicating that plants experienced stress in the W3 treatment. However, the agronomic traits and yields of okra in the N1 treatment were higher than those in the N0 and N1 treatments, indicating that the crop damage caused by W3 could be mitigated by an appropriate amount of N application. The N1W1 treatment emerged as the most suitable combination for okra growth in this study, exhibiting the highest stem diameter, leaf count, photosynthetic characteristics, and yield (201.3 g). Notably, this yield was 67.8% higher than the lowest treatment (N2W3), signifying a significant improvement.

Can Trichoderma harzianum be used to enhance the yield and nutrient uptake of Lactuca sativa cv “Lollo Rosso” in floating systems?

AbstractAn experiment was performed to evaluate the effect of Trichoderma harzianum MVT801 combined with different ratios of nutrient solution (NR) (25%, 50%, and 100%) on the growth and physiological traits of Lactuca sativa “Lollo Rosso” plants cultivated in floating systems. Inoculation of lettuce plants with T. harzianum MVT801 (T1) in a floating system improves biometric properties, photosynthetic parameters, and nutrient uptake compared with uninoculated treatment (T0). The results clearly showed that in T1, despite a 50% reduction in the ratio of nutrient solution, no significant difference was observed in the growth and photosynthesis characteristics and nutrient uptake in L. sativa “Lollo Rosso” leaves compared with a complete nutrient solution treatment (100%), which is one of the notable results of this study. In this regard, the highest yield was observed in T1NR50 (inoculated with fungi and 50% of the nutrient solution) and T1NR100 (inoculated with fungi and complete nutrient solution) treatments. Also, the highest concentrations of phosphorus and potassium in “Lollo Rosso” leaves were observed in T1NR50 and T1NR100 treatments. Accordingly, the use of T. harzianum in floating lettuce cultivation could be recommended to increase crop productivity and reduce the use of chemical fertilizers.

Effect of Pruning Treatment on Growth Characteristics and Metabolites in Eucommia ulmoides Oliver (E. ulmoides)

The effect of pruning treatments on growth, photosynthesis characteristics, and metabolites were was studied in Eucommia ulmoides Oliver (E. ulmoides). The experiment was carried out from March–August 2019. Three treatments were used: non-pruned trees (CK), a height of 20 cm above the top edge of the flowerpot (T1), and a height of 10 cm above the top edge of the flowerpot (T2). The results showed that the branches branch number, leaves leaf number, and stem diameter increased significantly (p < 0.05) in pruning treatments compared with CK. Similarly, the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), maximum photosynthetic efficiency (Fv/Fm), and non-photochemical quenching coefficient (NPQ) increased significantly in pruning treatments (p < 0.05). Interestingly, the contents of Chl a, Chl b, Chl, Car, and the rate between the Chl a content and the Chl b content increased significantly (p < 0.05) in T2, respectively. These verified that it was a better way to enhance the plants growth of E. ulmoides for pruning treatments. The GC-MS analysis showed that 36 different primary metabolites were identified, including 11 sugars, 13 acids, 5 alcohols, and 7 other compounds, the relative content of their metabolites were was higher in the T2 treatment than that in the T1 treatment, which was mainly concentrated in four main enrichment pathways (Galactose metabolism; Citrate cycle; Glyoxylate and dicarboxylate metabolism; and starch and sucrose metabolism) via KEGG analysis. Meanwhile, correlation analysis showed there were was a positive correlation between the accumulation of D-Galactose, D-Mannose, Succinic acid, and photosynthetic pigment content, and the rate of photosynthesis in T2 treatment (p < 0.05). The pruning height above the top edge of the flowerpot changed the accumulation of primary metabolites and promoted plant regeneration ability in E. ulmoides. Finally, the yield of main secondary metabolites from leaves (Genipin, Geniposide, Geniposidic acid, and Pinoresinol diglucoside) were was increased in pruning treatments by UPLC analysis. It provided a reference for the directional ecological cultivation of E. ulmoides.

Row ratio increasing improved light distribution, photosynthetic characteristics, and yield of peanut in the maize and peanut strip intercropping system.

Changes in the canopy microclimate in intercropping systems, particularly in the light environment, have important effects on the physiological characteristics of photosynthesis and yield of crops. Although different row ratio configurations and strip widths of dwarf crops in intercropping systems have important effects on canopy microclimate, little information is available on the effects of intercropping on chlorophyll synthesis and photosynthetic physiological properties of dwarf crops. A 2-year field experiment was conducted in 2019 and 2020, with five treatments: sole maize (SM), sole peanut (SP), four rows of maize intercropping with eight rows of peanut (M4P8), four rows of maize intercropping with four rows of peanut (M4P4), and four rows of maize intercropping with two rows of peanut (M4P2). The results showed that the light transmittance [photosynthetically active radiation (PAR)], photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) of intercropped peanut canopy were reduced, while the intercellular carbon dioxide concentration (Ci) was increased, compared with SP. In particular, the M4P8 pattern Pn (2-year mean) was reduced by 5.68%, 5.33%, and 5.30%; Tr was reduced by 7.41%, 5.45%, and 5.95%; and Gs was reduced by 8.20%, 6.88%, and 6.46%; and Ci increased by 11.95%, 8.06%, and 9.61% compared to SP, at the flowering needle stage, pod stage, and maturity, respectively. M4P8 improves the content of chlorophyll synthesis precursor and conversion efficiency, which promotes the utilization efficiency of light energy. However, it was significantly reduced in M4P2 and M4P4 treatment. The dry matter accumulation and pod yield of peanut in M4P8 treatment decreased, but the proportion of dry matter distribution in the late growth period was more transferred to pods. The full pod number decreases as the peanut row ratio decreases and increases with year, but there is no significant difference between years. M4P8 has the highest yield and land use efficiency and can be used as a reference row ratio configuration for maize-peanut intercropping to obtain relatively high yield benefits.

A genomic panel for studying C3-C4 intermediate photosynthesis in the Brassiceae tribe.

Research on C4 and C3-C4 photosynthesis has attracted significant attention because the understanding of the genetic underpinnings of these traits will support the introduction of its characteristics into commercially relevant crop species. We used a panel of 19 taxa of 18 Brassiceae species with different photosynthesis characteristics (C3 and C3-C4) with the following objectives: (i) create draft genome assemblies and annotations, (ii) quantify orthology levels using synteny maps between all pairs of taxa, (iii) ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠describe the phylogenetic relatedness across all the species, and (iv) track the evolution of C3-C4 intermediate photosynthesis in the Brassiceae tribe. Our results indicate that the draft de novo genome assemblies are of high quality and cover at least 90% of the gene space. Therewith we more than doubled the sampling depth of genomes of the Brassiceae tribe that comprises commercially important as well as biologically interesting species. The gene annotation generated high-quality gene models, and for most genes extensive upstream sequences are available for all taxa, yielding potential to explore variants in regulatory sequences. The genome-based phylogenetic tree of the Brassiceae contained two main clades and indicated that the C3-C4 intermediate photosynthesis has evolved five times independently. Furthermore, our study provides the first genomic support of the hypothesis that Diplotaxis muralis is a natural hybrid of D. tenuifolia and D. viminea. Altogether, the de novo genome assemblies and the annotations reported in this study are a valuable resource for research on the evolution of C3-C4 intermediate photosynthesis.

Photosynthesis in the Biomass Model Species Lemna minor Displays Plant-Conserved and Species-Specific Features.

Lemnaceae are small freshwater plants with extraordinary high growth rates. We aimed to test whether this correlates with a more efficient photosynthesis, the primary energy source for growth. To this end, we compared photosynthesis properties of the duckweed Lemna minor and the terrestrial model plant Arabidopsis thaliana. Chlorophyll fluorescence analyses revealed high similarity in principle photosynthesis characteristics; however, Lemna exhibited a more effective light energy transfer into photochemistry and more stable photosynthesis parameters especially under high light intensities. Western immunoblot analyses of representative photosynthesis proteins suggested potential post-translational modifications in Lemna proteins that are possibly connected to this. Phospho-threonine phosphorylation patterns of thylakoid membrane proteins displayed a few differences between the two species. However, phosphorylation-dependent processes in Lemna such as photosystem II antenna association and the recovery from high-light-induced photoinhibition were not different from responses known from terrestrial plants. We thus hypothesize that molecular differences in Lemna photosynthesis proteins are associated with yet unidentified mechanisms that improve photosynthesis and growth efficiencies. We also developed a high-magnification video imaging approach for Lemna multiplication which is useful to assess the impact of external factors on Lemna photosynthesis and growth.

Identification of Photosynthesis Characteristics and Chlorophyll Metabolism in Leaves of Citrus Cultivar (Harumi) with Varying Degrees of Chlorosis.

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

Features of Photosynthesis in Arabidopsis thaliana Plants with Knocked Out Gene of Alpha Carbonic Anhydrase 2.

The knockout of the At2g28210 gene encoding α-carbonic anhydrase 2 (α-CA2) in Arabidopsis thaliana (Columbia) led to alterations in photosynthetic processes. The effective quantum yields of both photosystem II (PSII) and photosystem I (PSI) were higher in α-carbonic anhydrase 2 knockout plants (α-CA2-KO), and the reduction state of plastoquinone pool was lower than in wild type (WT). The electron transport rate in the isolated thylakoids measured with methyl viologen was higher in α-CA2-KO plants. The amounts of reaction centers of PSII and PSI were similar in WT and α-CA2-KO plants. The non-photochemical quenching of chlorophyll a fluorescence in α-CA2-KO leaves was lower at the beginning of illumination, but became slightly higher than in WT leaves when the steady state was achieved. The degree of state transitions in the leaves was lower in α-CA2-KO than in WT plants. Measurements of the electrochromic carotenoid absorbance shift (ECS) revealed that the light-dependent pH gradient (ΔpH) across the thylakoid membrane was lower in the leaves of α-CA2-KO plants than in WT plants. The starch content in α-CA2-KO leaves was lower than in WT plants. The expression levels of the genes encoding chloroplast CAs in α-CA2-KO changed noticeably, whereas the expression levels of genes of cytoplasmic CAs remained almost the same. It is proposed that α-CA2 may be situated in the chloroplasts.

Beneficial Role of Multi-Walled Carbon Nanotubes on Physiological and Phytochemical Responses of Mentha piperita L under Salinity Stress

MWCNTs (Multiwalled Carbon Nanotubes) are nanomaterials that can enter the soil through various sources. Our understanding of the effects of MWCNT on plant growth is not yet complete and needs to be further studied. In this study, the possible effects of MWCNTs (0, 50 μg/ml, 200 μg/ml) on the growth, physiological, and phytochemical performance of Mentha piperita plants under 50, 100, and 200 mM NaCl stress in greenhouse conditions were investigated. Changes in the essential oil of M. piperita were analyzed by GC. The most physiological and photosynthesis characteristics of M. piperita seedlings were negatively affected when plants were grown at different concentrations of NaCl. With increasing the salt concentration to 200 mM, a significant decrease was observed in the fresh and dry weight of the plant and the number of plant branches. The presence of both doses of MWCNTs significantly enhanced relative water content (RWC), chlorophyll content, growth indices, and essential oil percentage. Also, the plants treated with both MWCNTs and NaCl showed higher antioxidant enzyme activities such as superoxide catalase and peroxidase content under salinity stress. Among the different concentrations of carbon nanotubes, 200 μg/ml has a potential effect on physiological and biochemical parameters in plants under salinity stress. It is proposed that MWCNTs can significantly improve growth and salt tolerance in M. piperita plants by promoting water uptake, antioxidant enzyme activity, and photosynthesis performance. It can be concluded that MWCNTs improved the stress condition for the plant and reduced the plant's metabolic response to stress.

Effects of nitrogen application level on the physiological characteristics, yield and fruit quality of blackberry

To study the optimal amount of nitrogen application for blackberry plants, different amounts of ammonium sulfate were applied to three-year-old healthy ‘Shuofeng’ blackberry plants at three key growth stages (early bud burst, the flowering stage and the fruit veraison stage) to explore the effects of nitrogen fertilizer application level on the physiological characteristics of leaves, yield and fruit quality of blackberry. Overall, the leaves turned yellow, and cellular metabolism was disrupted in the CK group (no nitrogen fertilization). Among the nitrogen treatments, the leaf chlorophyll content, photosynthesis efficiency and antioxidant enzyme activity were significantly higher under the T2 (40 g plant−1) and T3 (60 g plant−1) treatments than under the T1 (20 g plant−1) and T4 (80 g plant−1) treatments, while the contents of ascorbic acid, glutathione, hydrogen peroxide and malondialdehyde showed the opposite trends. The yield, single-fruit weight, solids–acids ratio and anthocyanin contents of blackberry fruits increased first and then decreased with increasing nitrogen application. The contents of polyphenols and ellagic acid in fruits decreased with increasing nitrogen application. Correlation and principal component analysis showed that yield and its components were closely related to leaf photosynthesis characteristics and the antioxidant system (P<0.05). Application of 20 g ammonium sulfate per plant at early bud burst, the flowering stage and the fruit veraison stage was profitable, which resulted in more vigorously growth, increased yield and fruit quality, while the production cost was the most economical because of the low fertilizer consumption.

Characteristics of photosynthesis and vertical canopy architecture of citrus trees under two labor-saving cultivation modes using unmanned aerial vehicle (UAV)-based LiDAR data in citrus orchards.

Analyzing and comparing the effects of labor-saving cultivation modes on photosynthesis, as well as studying their vertical canopy architecture, can improve the tree structure of high-quality and high-yield citrus and selection of labor-saving cultivation modes. The photosynthesis of 1080 leaves of two labor-saving cultivation modes (wide-row and narrow-plant mode and fenced mode) comparing with the traditional mode were measured, and nitrogen content of all leaves and photosynthetic nitrogen use efficiency (PNUE) were determined. Unmanned aerial vehicle (UAV)-based light detection and ranging (LiDAR) data were used to assess the vertical architecture of three citrus cultivation modes. Results showed that for the wide-row and narrow-plant and traditional modes leaf photosynthetic CO2 assimilation rate, stomatal conductance, and transpiration rate of the upper layer were significantly higher than those of the middle layer, and values of the middle layer were markedly higher than those of the lower layer. In the fenced mode, a significant difference in photosynthetic factors between the upper and middle layers was not observed. A vertical canopy distribution had a more significant effect on PNUE in the traditional mode. Leaves in the fenced mode had distinct photosynthetic advantages and higher PNUE. UAV-based LiDAR data effectively revealed the differences in the vertical canopy architecture of citrus trees by enabling calculating the density and height percentile of the LiDAR point cloud. The point cloud densities of three cultivation modes were significantly different for all LiDAR density slices, especially at higher canopy heights. The labor-saving modes, particularly the fenced mode, had significantly higher height percentile data.

Photosynthesis Characteristics of Tomato Plants and Its’ Responses to Microclimate in New Solar Greenhouse in North China

With the increasing demand for vegetable fruits, vegetable plants are moved to protected structures for achieving high production and economic revenue, especially in undesirable seasons. In North China, tomato crops, as widely consumed vegetables, are now increasingly planted in solar greenhouses (GH), especially in the winter period. To improve the microclimate inside GH in winter, a sunken solar greenhouse was used recently. This study was to evaluate the photosynthetic characteristics of tomato plants and its responses to the inside microclimate in this new GH. In this experiment, the plant transpiration (E) and photosynthesis (Pn) rates of healthy and diseased plants were measured from July to December for three growth seasons in a commercial GH in North China. Results show both E and Pn were positively related to inside radiation and vapor pressure deficit. The stomata conductance to E (gsw) and Pn (gtc) performed relatively constant during daytime, and weakly related to inside microclimate. The parameters of E, Pn, gsw and gtc were greatly reduced for diseased plants in summer because of the heat shock. The water use efficiency at the leaf level, the ratio of Pn to E, was higher for solar radiation of 400–500 W m−2, temperature of 20–30 °C, relative humidity of higher than 80%, and vapor pressure deficit of less than 2.0 kPa. The results of this study could help farmers in the region of 30 to 40 degrees north latitude to enhance the growth of tomato crops in winter by using this sunken solar greenhouse.

Progress on photosynthetic nitrogen assimilation and its regulatory mechanisms in cyanobacteria

水华蓝藻的生物学特性及其竞争优势、蓝藻水华的形成与维持机制等科学问题，一直是国内外研究的热点。氮素是诱发蓝藻水华暴发的重要营养盐，蓝藻对氮素的同化与其光合作用密切偶联。然而，水体中氮素存在多种形态，不同形态氮素对蓝藻生长和水华发生的影响具有显著差异。因此，了解蓝藻光合作用特征及其同化不同形态氮素的机制和策略，对深入理解蓝藻水华的发生机理具有重要意义。本文在蓝藻的光能捕获与激发能转移、光合电子传递、碳浓缩机制及CO₂同化等光合作用过程及其特征综述的基础上，对蓝藻摄取、同化5种主要氮素形态（NO₃^-、NO₂^-、NH₄⁺、尿素和N₂）的分子机制及其特征进行了解读，总结了蓝藻细胞光合碳、氮同化的耦合关系及调控机制；并指出了该领域的未来发展方向，以推动该方向的深入研究。;The biological characteristics and competitive predominance of cyanobacteria, as well as the formation and maintenance mechanism of cyanobacteria blooms, have aroused continuous interests among researchers. As an important nutrient for cyanobacterial growth, the assimilation of nitrogen is intimately coupled with the photosynthesis. However, nitrogen exists in various chemical forms in water, which affect the cyanobacterial growth and the formation of blooms in distinct ways. To delve into the formation mechanism of cyanobacterial blooms, it is important to understand the cyanobacterial photosynthetic feature as well as the mechanism and strategy by which the nitrogen of different forms are assimilated into cyanobacteria. This paper reviewed the processes and characteristics of photosynthesis in cyanobacteria, such as light energy capture and excitation energy transfer, primary photosynthetic reaction, CO₂ concentrating mechanism and assimilation. Then, it illustrated the transport and assimilation of different nitrogen forms (NO₃^-, NO₂^-, NH₄⁺, urea and N₂), the regulation of these processes, as well as the mechanisms by which cells coordinate and regulate the carbon/nitrogen metabolism. The paper also summarized the latest research advances in cyanobacterial blooms and suggested on the content and direction of further research.

Effects of different nitrogen forms on photosynthesis characteristics and growth of poplar

Effects of different nitrogen forms on photosynthesis characteristics and growth of poplar

Optimized Planting Density and Nitrogen Rate Increased Grain Yield and Water-Nitrogen Use Efficiency of Two Maize Cultivars under Mulched Drip Fertigation by Improving Population Photosynthesis and Grain-Filling Characteristics

The characteristics of photosynthesis and grain filling play a significant role in determining maize (Zea mays L.) yield. Planting density and nitrogen (N) rate are two factors affecting the growth, physiology, and grain yield of maize. The coupling effects of planting density and N rate on individual and population photosynthetic rates, grain-filling characteristics, grain yield, water use efficiency (WUE), and N partial factor productivity (NPFP) of two maize cultivars (QS51 and ZD958) under mulched drip fertigation in northwest China were investigated. Three planting densities (D1: 80,000 plants ha−1, D2: 100,000 plants ha−1, and D3: 120,000 plants ha−1) and three N rates (N0: 0 kg ha−1, N180: 180 kg ha−1, and N240: 240 kg ha−1) were designed. The results showed that the population photosynthetic rate, grain yield, WUE, and NPFP were significantly affected by planting density and N rate for both QS51 and ZD958, and their interaction had a significant effect on grain yield, WUE, and NPFP. Nitrogen application significantly improved grain-filling rates compared with N0, but there was no significant difference between N240 and N180. The D2N180 treatment obtained the maximum grain yield (15,693 kg ha−1 for QS51 and 17,644 kg ha−1 for ZD958), WUE (3.42 kg kg−1 for QS51 and 3.05 kg kg−1 for ZD958), and NPFP (98.37 kg kg−1 for QS51 and 83.93 kg kg−1 for ZD958). It was concluded that the optimized planting density and N rate improved grain yield and water-nitrogen use efficiency of QS51 and ZD958 by increasing population photosynthetic rate, grain-filling rate, and grain weight. This study enhanced our understanding of how optimized planting density and N rate maintained the sustainable maize production under mulched drip fertigation in northwest China.

Photosynthesis Intensity in Frequently Used Woody Plants

Photosynthesis is a vital source of energy in nature. Various methods for determining the intensity of photosynthesis in plants make it possible to unambiguously compare all available experimental data and general conclusions about the features of photosynthesis in plants. Research objectives: determination of the intensity of photosynthesis in woody plants. Collection of data on the intensity of photosynthesis of the studied plant species in the first and second years and determination of the influence of external factors of temperature, light intensity, CO2 and O2 concentrations in the air, air and soil humidity on the photosynthesis process. Research results: low intensity of photosynthesis is observed in species growing in areas with a temperate or mild climate. Conclusion: plant species that live mainly in areas with a continental climate or. in mountainous conditions have a high intensity of photosynthesis.

Effects of exogenous Strigolactone on the physiological and ecological characteristics of Pennisetum purpureum Schum. Seedlings under drought stress

BackgroundDrought is one of the main environmental factors limiting plant growth and development. Pennisetum purpureum Schum. was used to explore the mitigation effects of exogenous strigolactone (SL) on drought stress during the seedling stage. The effects of different concentrations (1, 3, 5, and 7 μmol·L− 1) of SL on the photosynthesis characteristics, growth performance, and endogenous abscisic acid (ABA) of P. purpureum under drought stress were studied.ResultsExogenous SL could effectively alleviate the inhibitory effect of drought stress on P. purpureum growth. Compared with drought stress, the net photosynthesis rate, stomatal conductance, transpiration rate, and water-use efficiency of the leaves of P. purpureum after SL treatment significantly increased, thereby exerting a significant mitigation effect on the decrease in photosystem II maximum photochemical efficiency and the performance index based on light absorption caused by drought. Moreover, the exogenous application of SL can effectively increase the fresh and dry weight of the leaves and roots and the main-root length. After applying SL for 120 h, the ABA content of P. purpureum decreased significantly. The activity of key enzymes of photosynthesis significantly increased after 48 h of external application of SL to P. purpureum.ConclusionsSL treatment can improve the photosynthesis performance of P. purpureum leaves under drought conditions and increase the antioxidant capacity of the leaves, thereby reducing the adverse effects of drought, promoting the growth of P. purpureum, and effectively improving the drought resistance of P. purpureum.

Interannual and seasonal relationships between photosynthesis and summer soil moisture in the Ili River basin, Xinjiang, 2000–2018

Soil moisture (SM) is essential for controlling terrestrial carbon uptake, as it directly provides moisture for photosynthesis, especially in arid and semiarid regions. We selected the arid and semiarid Ili River basin (IRB) of Xinjiang as the study area, and investigated the spatial and temporal characteristics and interrelationships with SM and photosynthesis from 2000 to 2018 using the ERA5 products and solar-induced chlorophyll fluorescence (SIF). SM and photosynthesis showed a decreasing trend during the study period. Compared with those in spring and autumn, the variation of summer SM and SIF was more consistent with the interannual variation. Anomaly analysis showed that negative SM anomalies were most profound in 2012–2015, 2008, and 2014. Additionally, we quantified the effect of seasonal SM deficits on photosynthesis by performing model-based experiments. The results indicated that the gross primary productivity (GPP) simulated by the P-model could capture the characteristics of photosynthesis in the IRB, which had a high correlation with SIF (R2 = 0.82, p < 0.001). In 2012–2015, 2008, and 2014, SM deficits caused more GPP reduction in the summers than in the springs or the autumns. The trends were mainly visible in the northern IRB, where GPP was below 40 % of the multi-year mean, and SM was below 23 %. GPP decreased more significantly in grassland than in the forest under the influence of SM deficit. This study reveals seasonal differences in the effects of SM deficit on photosynthesis and emphasizes that the summer SM deficit was the main factor responsible for decreases in GPP in the IRB during the study period. These findings contribute to a better understanding of the relationships between photosynthesis and environmental factors, and provide a reference for an accurate assessment of the regional carbon cycle.

Grain-filling characteristics and yield formation of wheat in two different soil fertility fields in the Huang-Huai-Hai Plain.

Clarifying factors that underpinning the variation in wheat yield components between high and middle soil fertility fields is critical to increase grain production and narrow yield gap for smallholder farming systems in the Huang–Huai–Hai Plain (3HP), which characterized by a large variation in soil fertility. Two-year field experiments were conducted to investigate wheat tillering, leaf photosynthesis, and grain filling characteristics in different soil fertility fields: high soil fertility field (HF) and middle soil fertility field (MF). Results showed that the spike formation rate in HF was 12.7%–13.0% higher than that in MF, leading to an 18.0%–19.8% increase in spike number. In addition, HF improved canopy light interception and leaf photosynthesis characteristics after anthesis and delayed leaf senescence, contributing to the increase in both the active grain filling period and grain filling rate. This resulted in a higher 1,000 grain weight in HF, which was 8.2%–8.3% higher than that in MF. Compared to MF, HF obtained higher yields at 9,840 kg ha−1 in 2017/18 and 11,462 kg ha−1 in 2018/19, respectively. In summary, higher spike number and 1,000-grain weight, which were mediated by spike-formation rate, maximization of light interception and improved leaf photosynthesis. These results would have important implications for narrowing yield gap between MF and HF in the 3HP.