Quantifying the effects of plant density on soybean lodging resistance and growth dynamics in maize-soybean strip intercropping.

Shading-induced soybean stem lodging is a prevalent concern in the maize (Zea mays L.)-soybean (Glycine max L. Merr.) strip intercropping system, leading to a substantial decline in yield. Nevertheless, the associations between soybean growth, stem lodging, and yield formation in this scenario remain unclear. To investigate this, the logistic and beta growth models were utilized to analyze the growth process of soybean organs (stems, leaves, branches, and pods) and the accumulation of carbohydrates (lignin, cellulose, and sucrose) at three planting densities (8.5, 10, and 12.5 plants m-2) in both strip intercropping and skip strip monoculture systems. The results indicate that shading stress caused by maize in the intercropping system reduced lignin and cellulose accumulation in soybean stems, thus decelerating soybean organ growth compared to monoculture. Furthermore, intercropped soybean at higher planting density (PD3) exhibited a 28% reduction in the maximum dry matter growth rate (cm) and a 11% decrease in the time taken to reach the maximum dry matter growth rate (te) compared to the lower planting density (PD1). Additionally, a 29% decrease in the maximum accumulation rate (cmax) of sucrose, lignin, and cellulose was observed, along with a 13% decrease in the continuous accumulation time (tc) of these carbohydrates in intercropped soybean at PD3. Interspecific and intraspecific shading stress led to a preferential allocation of assimilates into soybean stems, enhancing plant height during the initial stage, while at later stages, a greater proportion of sucrose was allocated to leaves. Consequently, this hindered the conversion of sucrose into lignin and cellulose within the stems, ultimately resulting in a reduction in the lodging resistance index (LRI). Overall, this study provides valuable insights into the effects of shading stress on soybean growth and yield. It also emphasizes how optimizing planting density in intercropping systems can effectively alleviate shading stress and enhance crop productivity.

Shade-Tolerant Soybean Reduces Yield Loss by Regulating Its Canopy Structure and Stem Characteristics in the Maize-Soybean Strip Intercropping System.

The shading of maize is an important factor, which leads to lodging and yield loss of soybean in the maize-soybean strip intercropping system, especially in areas with low solar radiation. This study was designed to explore how shade-tolerant soybean reduces yield loss by regulating its canopy structure and stem characteristics in the maize-soybean strip intercropping system. The soybean cultivars Tianlong No.1 (TL-1, representative of shade-tolerant plants) and Chuandou-16 (CD-16, representative of shade-intolerant plants) were grown in monocropping and intercropping systems from 2020 to 2021 in Chongzhou, Sichuan, China. Regardless of shade-intolerant or shade-tolerant soybean, the canopy and stem of soybean in strip intercropping were weaker than those of the corresponding monoculture. But compared with shade-intolerant soybean, the shade-tolerant soybean slightly changed its spatial structure of canopy and stem morphology and physiology in maize-soybean strip intercropping system, especially in the later growth stages. On the one hand, the canopy of shade-tolerant soybean showed relatively high transmission coefficient (TC) and relatively low leaf area index (LAI) and mean leaf angle (MLA). On the other hand, the stem of shade-tolerant soybean was obviously stronger than that of shade-intolerant soybean in terms of external morphology, internal structure, and physiological characteristics. Additionally, compared with shade-intolerant soybean, shade-tolerant soybean showed higher APnWP (the average net photosynthetic rate of the whole plant) and seed yield in the strip intercropping. The results showed that shade-tolerant soybean increased light energy capture and photosynthesis in the different canopy levels to promote the morphological and physiological development of the stem and ultimately reduce the yield loss of the strip intercropping system. However, the molecular mechanism of low radiation regulating soybean canopy structure (LAI, TC, and MLA) needs further in-depth research to provide theoretical guidance for cultivating plants with ideal canopy shape that can adapt to changing light environment in intercropping system.

Transcriptome Analysis Reveals Complex Molecular Mechanisms Underlying UV Tolerance of Wheat ( Triticum aestivum, L.).

Plants have inherent tolerance to UV stress. However, very limited information is available about how wheat perceives and defends against UV disaster. To obtain the molecular mechanisms underlying UV tolerance of wheat, the phenotypic and transcriptomic responses of ZN168 and ZKM138 with contrasting UV tolerance were characterized. Compared with ZKM138, ZN168 showed significantly less UV damage. High-throughput sequencing revealed that UV stress inhibited the expression of genes related to photosynthesis and carbon fixation and a less degree for ZN168 than ZKM138. The distinctive performance of ZN168 is mediated by the selective expression of genes involved in multiple defense responses. Besides, metabolome analysis on grains suggested that UV radiation had a significant effect on anthocyanin accumulation. This study will enable us to exploit genes pinpointed as the targets of genetic engineering, thereby improving the UV tolerance of wheat. Furthermore, the anthocyanin-enriched wheat can be excellent resources to act as functional food.