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Plant photosynthetic capacity directly determines crop yield. Light quality regulates photosynthetic capacity. This review discusses plant responses to far-red light from the phenotypic to the molecular level, focusing specifically on the improvement of photosynthetic capacity by adjustment of photosynthetic electron transport and the path of light energy. Far-red light can also regulate leaf angle and increase plant height and leaf area, via expression of associated genes, to capture more light energy. Thus, far-red light regulates plant morphology and photosynthetic capacity. Identifying the mechanism of this regulation may lead to increased crop yields.

Plants are frequently exposed to adverse environments during their life span. Among them drought stress is one of the major threats to agricultural productivity. In order to survive in such unstable environment, plants have developed mechanisms through which they recognize the severity of the stress based on the incoming environmental stimuli. To combat the detrimental effects of drought, the plants have evolved various strategies to modulate their physio-hormonal attributes. These strategies that can be modulated by shade and microbes contribute to enhancing tolerance to drought and reducing yield loss. Plant hormones, such as abscisic acid, auxin and ethylene have a major role in the shade- and microbe-associated improvement of drought tolerance through their effects on various metabolic pathways. In this process, the CLAVATA3/EMBRYOSURROUNDING REGION-RELATED 25 peptide has a major role due to its effect on ABA synthesis as shown in our regulatory model.

A field experiment was conducted in 2018–2020 to investigate the effect of two nitrogen application rates (N0 = 0 kg ha−1(control), N90 = 90 kg ha−1, and N180 = 180 kg ha−1) on morphological and physiological behaviours of two new rapeseed varieties; V1 = JYJS01 (semi-dwarf variety) and V2 = CY36 (tall variety). Our results indicated that N application enhanced the plant growth and seed protein content in comparison to control. Contrastingly, compared with control, sugar contents, i.e. sucrose and reducing sugars, decreased significantly in response to an increase in N. Seed oil content also decreased by 8.5% and 5.5%, 6.7% and 3.9% against N180 in V1 and V2 during 2019 and 2020, respectively. Furthermore, higher nitrogen application rates decreased seed fatty acid proportions by decreasing the sugar availability for fatty acid biosynthesis. Our results demonstrated the highest seed yield (9.4 g plant−1 in 2018/19 and 9.5 g plant−1 in 2019/20) in V2 against N180, and the lowest seed yield (3.2 g plant−1 in 2018/19 and 3.4 g plant−1 in 2019/20) in V1 at control. These findings imply that a high nitrogen application rate had increased the yield. At the same time, the carbohydrates translocation from stems to seed for fatty acid biosynthesis decreased, which played their significant role in seed physiology for fatty acid metabolisms, ultimately affected the seed quality. However, there is still a dire need to evaluate how nitrogen application affect the carbohydrate availability for fatty acid metabolism in the seed of new winter rapeseed varieties.

An experiment was set up to investigate physiological responses of soybeans to silicon (Si) under normal light and shade conditions. Two soybean varieties, Nandou 12 (shade resistant), and Nan 032–4 (shade susceptible), were tested. Our results revealed that under shading, the net assimilation rate and the plant growth were significantly reduced. However, foliar application of Si under normal light and shading significantly improved the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and decreased intercellular carbon dioxide concentration (Ci). The net photosynthetic rate of Nandou 12 under normal light and shading increased by 46.4% and 33.3% respectively with Si treatment (200 mg/kg) compared to controls. Si application also enhanced chlorophyll content, soluble sugars, fresh weight, root length, root surface area, root volume, root-shoot ratio, and root dry weight under both conditions. Si application significantly increased the accumulation of some carbohydrates such as soluble sugar and sucrose in stems and leaves ensuring better stem strength under both conditions. Si application significantly increased the yield by increasing the number of effective pods per plant, the number of beans per plant and the weight of beans per plant. After Si treatment, the yield increased 24.5% under mono-cropping, and 17.41% under intercropping. Thus, Si is very effective in alleviating the stress effects of shading in intercropped soybeans by increasing the photosynthetic efficiency and lodging resistance.

Shading is one of the most chronic restrains which can lead to the lodging of intercropped plants. In order to increase the soybean stem lodging resistance, a 2-year field trial was conducted to evaluate the impact of different ratios and concentrations of NH4+/NO3– on the morpho-physiological and biochemical characteristics of soybean stem under shade conditions. The total 5 ratios of NH4+/NO3– were applied as follows: T0 = 0/0 (control), T1 = 0/100 (higher ratio), T2 = 25/75 (optimum), T3 = 50/50 (optimum), and T4 = 75/25 (higher ratio) as a nitrogen source. Our findings displayed that the T2 (25/75) and T3 (50/50) treatments alleviated the shading stress by improving the photosynthetic activity, biomass accumulation, carbohydrates contents, and lignin related enzymes (POD, CAD, and 4Cl) which led to improvement in stem lodging resistance. The correlation analysis (p ≤ 0.05, p ≤ 0.01) revealed the strong relationship between lodging resistance index and stem diameter, stem strength, lignin content, photosynthesis, and lignin related enzymes (POD, CAD, and 4CL) evidencing the strong contribution of lignin and its related enzymes in the improvement of lodging resistance of soybean stem under shade conditions. Collectively, we concluded that optimum NH4+/NO3– ratios (T2 and T3) can boost up the lodging resistance of soybean stem under shade stress.

In maize-soybean intercropping system, shade is the major chronic restrain that effected the normal growth of soybean. Different spatial patterns of this system have affected the microclimate of soybean by shading of maize plants. However, the negative impacts of shading stress can be mitigated by providing the optimal ratios of different fertilizers. Therefore, to test this hypothesis, the soybean plants were grown under different light conditions (normal light and shade) to evaluate the response to varying NH4 + /NO3 - ratios. The seed of soybean (Glycine max L. cultivar of "Nan-99-6") were grown in nutrient solution at a total concentration of 5mM N using different NH4 + /NO3 - ratios (To= 0:0, T1= 0:100, T2= 25:75, T3=50:50, and T4= 75:25) for 40 days in greenhouse at PPFD 320.95 μmolm-2 s-1 (low light intensity) and 967.53 μmolm-2 s-1 (normal light intensity). Under low light the growth and photosynthesis of soybean seedlings had significantly decreased as compared to normal light conditions. Nonetheless, the optimal ratios of NH4 + /NO3 - had improved the growth and photosynthesis activities of soybean seedlings under both light conditions. Our results indicated that soybean seedlings supplied with optimal NH4 + /NO3 - ratios (25:75 and 50:50) have showed the maximum biomass yield, chlorophyll pigments, leaf gas exchange, photochemical activities and root growth as compared to high NH4 + /NO3 - ratios (T1 and T4). Since, the higher ratios of NH4 + /NO3 - resulted in lower plant growth due to accumulation in plant tissues; therefore, we suggested that optimal ratios of NH4 + /NO3 - can enhance the shade resistance of soybean seedlings.

Under natural conditions, plants constantly encounter various biotic and abiotic factors, which can potentially restrict plant growth and development and even limit crop productivity. Among various abiotic factors affecting plant photosynthesis, light serves as an important factor that drives carbon metabolism in plants and supports life on earth. The two components of light (light quality and light intensity) greatly affect plant photosynthesis and other plant’s morphological, physiological and biochemical parameters. The response of plants to different spectral radiations and intensities differs in various species and also depends on growing conditions. To date, much research has been conducted regarding how different spectral radiations of varying intensity can affect plant growth and development. This review is an effort to briefly summarize the available information on the effects of light components on various plant parameters such as stem and leaf morphology and anatomy, stomatal development, photosynthetic apparatus, pigment composition, reactive oxygen species (ROS) production, antioxidants, and hormone production.

Soybean (Glycine max L.) has been extensively cultivated in maize–soybean relay intercropping systems in southwest China. However, during the early co-growth period, soybean seedlings suffer from severe shading by maize resulting in lodging and significant yield reduction. The purpose of the present research was to investigate the reasons behind severe lodging and yield loss. Therefore, four different soybean genotypes (B3, B15, B23, and B24) having different agronomic characteristics were cultivated in intercropping and monocropping planting patterns. The results showed that under different planting patterns, the stem resistance varied among genotypes (P < 0.01). The lodging resistance index of B3, B15, B23, and B24 genotypes was 70.9%, 60.5%, 65.2%, and 57.4%, respectively, under intercropping, among which the B24 genotype was less affected by the shade environment as there was little decrease in the lodging resistance index of this genotype under intercropping. The lignin content of B23 and B24 was significantly higher than that of B3 and B15 under both planting patterns. Under intercropping, the hemicellulose content of B23 and B24 stems was significantly higher than that of B3 and B15. Compared to the monocropping, the content of mannose in the structural carbohydrate of soybean stems was decreased in all genotypes except B23, but the difference was not significant. The content of xylose in the structural carbohydrate of soybean stems was significantly higher than that in B3 and B15. Mannose content showed no significant difference among genotypes. The arabinose content of B24 was significantly higher than that of B3, B15, and B23. The effective pod number, seed number per plant, seed weight per plant and yield of soybean plants were significantly decreased under intercropping. Conclusively, manipulation of structural and nonstructural carbohydrate rich soybean genotypes in intercropping systems could alleviate the yield loss due to lodging.

Shading is one of the most chronic restrains which can lead to the lodging of intercropped plants. In order to increase the soybean stem lodging resistance, a 2-year field trial was conducted to evaluate the impact of different ratios and concentrations of NH

Phosphorus (P) is an essential macronutrient needed for plant growth, development, and production. A deficiency of P causes a severe impact on plant development and productivity. Several P-based fertilizers are being used in agriculture but limited uptake of P by the plant is still a challenge to be solved. Titanium (Ti) application increases the nutrient uptake by affecting the root growth; however, the role of Ti in plant biology, specifically its application under low light and phosphorus stress, has never been reported. Therefore, a pot study was planned with foliar application of Ti (in a different concentration ranging from 0 to 1,000 mg L–1) under different light and P concentrations. The result indicated that under shade and low P conditions the foliar application of Ti in different concentrations significantly improves the plant growth parameters such as root length, root surface area, root dry matter, and shoot dry matters. The increase was observed to be more than 100% in shade and low P stressed soybean root parameter with 500 mg L–1 of Ti treatment. Ti was observed to improve the plant growth both in high P and low P exposed plants, but the improvement was more obvious in Low P exposed plants. Auxin concentration in stressed and healthy plant roots was observed to be slightly increased with Ti application. Ti application was also observed to decrease rhizosphere soil pH and boosted the antioxidant enzymatic activities with an enhancement in photosynthetic efficiency of soybean plants under shade and P stress. With 500 mg L–1 of Ti treatment, the photosynthetic rate was observed to improve by 45% under shade and P stressed soybean plants. Thus, this work for the first time indicates a good potential of Ti application in the low light and P deficient agricultural fields for the purpose to improve plant growth and development parameters.

A half-root stress is a half portion of the root system exposed to treatment while the remaining half portion kept under normal conditions. A half-root stress including half-root drought stress, half-root nutrient stress, and half-root salinity stress has become a general approach to improve plant performance and adaptability. Plants produce some chemical signals in stressed part of root, and other parts sense these signals to improve the acclimation and adaptive responses to environmental stresses. Plants adapt the compensatory functions and discriminate the systemic and local regulatory mechanisms, but the understanding of these mechanisms is controversial. Chemical signals (Abscisic acid, sap pH, cytokinins, content of malate, amino acid, and ureide) have been involved in root to shoot signaling under half-root stress. Furthermore, naturally appeared half-root stress in intercropping systems could be an additional attribute of half-root stress approach. Therefore, much more study is required to elaborate its acceptability in intercropping. In this review, we summarized the current knowledge and identified some key future researches areas regarding half-root stress approach.

We selected four genotypes from the recombinant inbred lines based on their agronomic traits in terms of lodging resistance. Then, we investigated the morphological characteristics and stem carbohydrate accumulation of different soybean (Glycine max L.) genotypes under different light environments (normal light, low light and shading stress). Based upon metabolic accumulation of carbohydrates in the stem, we explored the reasons for the differences in stem strength of different soybean genotypes and expounded the relationship between accumulation and distribution of carbohydrates. Results of the present study showed that with the advancement of soybean growth period, the cellulose and lignin contents in soybean stem increased while the hemicellulose, sucrose and soluble sugars contents decreased. Compared with normal light conditions, the lignin, cellulose, soluble sugar and sucrose contents in the soybean plants under shading stress were reduced to different levels. Moreover, low light significantly reduced non-structural carbohydrate content in soybean stem while the lignin and cellulose contents were not significantly changed. The correlation analysis showed that there was a significant positive correlation among the stem snapping resistance, cellulose and lignin contents. The results showed that the stem strength was mainly determined by lignin and cellulose contents. The lignin content in the stem had a greater effect on the stem strength compared to cellulose. The xylose in soybean stem was also significantly reduced under the shading stress, which reduced lignin synthesis substrates. Under low light and shading stress, the minimum decrease in sucrose and structural carbohydrates content of a genotype (B23) was noticed indicating that B23 had high stem strength and increased decomposition of sucrose into cellulose synthesis. This trait of increased decomposition reduces the plant’s inefficient decomposition of sucrose thus most of the sucrose is used to synthesize cellulose. Conclusively, these results suggested that deposition of a relatively large amount of structural carbohydrates (e.g. lignin, cellulose, hemicellulose and monosaccharides) leads to thicker stem tissues which could be helpful to reduce lodging due to shading stress under multiple cropping systems.

Phosphorus (P) is an essential macronutrient needed for plant growth, development, and production. A deficiency of P causes a severe impact on plant development and productivity. Several P-based fertilizers are being used in agriculture but limited uptake of P by the plant is still a challenge to be solved. Titanium (Ti) application increases the nutrient uptake by affecting the root growth; however, the role of Ti in plant biology, specifically its application under low light and phosphorus stress, has never been reported. Therefore, a pot study was planned with foliar application of Ti (in a different concentration ranging from 0 to 1,000 mg L–1) under different light and P concentrations. The result indicated that under shade and low P conditions the foliar application of Ti in different concentrations significantly improves the plant growth parameters such as root length, root surface area, root dry matter, and shoot dry matters. The increase was observed to be more than 100% in shade and low P stressed soybean root parameter with 500 mg L–1 of Ti treatment. Ti was observed to improve the plant growth both in high P and low P exposed plants, but the improvement was more obvious in Low P exposed plants. Auxin concentration in stressed and healthy plant roots was observed to be slightly increased with Ti application. Ti application was also observed to decrease rhizosphere soil pH and boosted the antioxidant enzymatic activities with an enhancement in photosynthetic efficiency of soybean plants under shade and P stress. With 500 mg L–1 of Ti treatment, the photosynthetic rate was observed to improve by 45% under shade and P stressed soybean plants. Thus, this work for the first time indicates a good potential of Ti application in the low light and P deficient agricultural fields for the purpose to improve plant growth and development parameters.

Shade is the main growth and yield limiting factor for soybean seedlings in maize-soybean relay strip intercropping. Therefore, a field experiment was conducted to investigate the effect of titanium (Ti) foliar application on soybean under a maize-soybean relay strip intercropping system. In this study, the soybean plants were sprayed with Ti treatments (T0S = 0, T1S = 125, T2S = 250, T3S = 500 and T4S = 1000 mg L−1) under maize-soybean relay strip intercropping. The results have indicated that under intercropping environment, Ti application significantly affected the growth of the plants. The soybean plants supplied with Ti treatment (T1S) significantly improved soybean diameter and stem strength at both V5 and R5 stages. Ti application resulted in a significant increase in SPAD values in T1S (i.e. 31.69 % and 21.21 %) and T2S (i.e. 21.55 % and 22.19 %) in comparison to control at both V5 and R5 stage, respectively. Furthermore, foliar application of Ti (T1S) significantly increased photosynthetic rate by 33.15 % and 22.80 % at both V5 and R5 stages. The stomatal conductance (Gs) increased significantly in T1S (44.39 %) and T2S (31.30 %) at the V5 stage and in T1S (29.85 %) at the R5 stage, respectively in comparison to control leading to increase root and shoot biomass in both V5 and R5 stages except for treatment T4S. Analysis of stem anatomical structure, stem strength (lodging resistance), and phosphorus content revealed that foliar application of Ti not only improved the shade tolerance but also increased yield (16–17 %) of soybean under maize-soybean relay strip intercropping. Conclusively, foliar application of Ti could be helpful in mitigating the shade stress and increasing soybean yield under the strip intercropping system.

Lodging is one of the most chronic restraints of the maize-soybean intercropping system, which causes a serious threat to agriculture development and sustainability. In the maize-soybean intercropping system, shade is a major causative agent that is triggered by the higher stem length of a maize plant. Many morphological and anatomical characteristics are involved in the lodging phenomenon, along with the chemical configuration of the stem. Due to maize shading, soybean stem evolves the shade avoidance response and resulting in the stem elongation that leads to severe lodging stress. However, the major agro-techniques that are required to explore the lodging stress in the maize-soybean intercropping system for sustainable agriculture have not been precisely elucidated yet. Therefore, the present review is tempted to compare the conceptual insights with preceding published researches and proposed the important techniques which could be applied to overcome the devastating effects of lodging. We further explored that, lodging stress management is dependent on multiple approaches such as agronomical, chemical and genetics which could be helpful to reduce the lodging threats in the maize-soybean intercropping system. Nonetheless, many queries needed to explicate the complex phenomenon of lodging. Henceforth, the agronomists, physiologists, molecular actors and breeders require further exploration to fix this challenging problem. National Key Research and Development Program of China | Ref. 2018YFD1000905 Sichuan Innovation Team Project of National Modern Agricultural Industry Technology System | Ref. SCCXTD−2020−20

In order to improve soybean's resistance to lodging, silicon (Si) solutions at concentrations of 0,100, 200,300 mg kg-1 were applied during the seedling stage. The Si accumulation in different parts of the plants, the photosynthetic parameters of leaves and chlorophyll content, the stem bending resistance, the expression of genes of lignin biosynthesis and associated enzyme activity and sap flow rates were measured at early and late growth stages. The potential mechanisms for how Si improve growth and shade tolerance, enhances lodging resistance and improves photosynthesis were analyzed to provide a theoretical basis for the use of Si amendments in agriculture. After application of Si at 200 mg kg-1, the net photosynthetic rate of soybeans increased by 46.4 % in the light and 33.3 % under shade. The application of Si increased chlorophyll content, and fresh weight of leaves, reduced leaf area and enhanced photosynthesis by increasing stomatal conductance. The activity of peroxidase (POD), 4-coumarate:CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD) and phenylalanine ammonia-lyase (PAL) increased during pre-and post-growth periods, whereas Si also increased lignin accumulation and inhibited lodging. We concluded that Si affects the composition of plant cell walls components, mostly by altering linkages of non-cellulosic polymers and lignin. The modifications of the cell wall network through Si application could be a useful strategy to reduce shading stress in intercropping.