Effects of contrasting shade treatments on the carbon production and antioxidant activities of soybean plants

Abstract

In China, maize-soybean relay-intercropping system follow the two main planting-patterns: (i) traditional relay-intercropping; maize-soybean equal row planting, where soybean experience severe maize shading on both sides of plants, and (ii) modern relay-intercropping; narrow-wide row planting, in this new planting pattern only one side of soybean leaves suffer from maize shading. Therefore, in this study, changes in morphological traits, cytochrome content, photosynthetic characteristics, carbon status, and the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were investigated at 30 days after treatment (DAT) in shade-tolerant soybean variety Nandou-12 subjected to three different types of shading conditions; normal light (NL, all trifoliate-leaves of soybean plants were under normal light); unilateral shade (US, all right-side trifoliate-leaves of soybean plants from top to bottom were under shade while all the left-side of trifoliate-leaves from top to bottom were in normal light); bilateral shade (BS, all trifoliate-leaves of soybean plants were under complete shade). Compared with BS, US conditions decreased plant height and increased stem diameter, leaf area, and biomass at 30 DAT. Biomass distribution rates to stem, petiole and leaves, and photosynthetic characteristics were markedly improved by the US at all sampling stages, which proved to be a better growing condition than BS with respect to shade tolerance. The enhanced net photosynthesis and transpiration rates in the left-side leaves (LS) of soybean plants in US, when compared with the LS in BS, allowed them to produce higher total soluble sugar (by 70%) and total soluble protein (by 17%) at 30 DAT which reduce the adverse effects of shading at right-side leaves (RS) of the soybean plants. Similarly, soybean leaves under US accumulated higher proline content in US than the leaves of BS plants. Soybean leaves grown in shading conditions (LS and RS of BS and RS of US) developed antioxidative defence-mechanisms, including the accelerated activities of SOD, POD, APX, and CAT. Comparatively, soybean leaves in US displayed lower activity levels of the antioxidative enzymes than the leaves of BS plants, showing that soybean plants experienced less shade stress in US as compared with BS treatment. Overall, these results indicate that the association of improved photosynthetic characteristics, sugar and protein accumulation and optimum antioxidative defences could be an effective approach for growing soybean in intercropping environments.

The fingerprints of climate warming on cereal crops phenology and adaptation options

“…Nevertheless, optimum planting geometry could improve resource use efficiencies in crops through proper crop phenology, producing more leaf area and ultimately more favorable yield components and yield in cereal crops in all climatic conditions 251,252 . Planting geometry affects solar radiation interception, canopy coverage, crop growth rate and biomass accumulation 215,[253][254][255][256][257][258] . Furthermore, with optimum planting geometry, total dry matter production and ultimately grain yield increase was mainly due to more photo-assimilates 252 .…”

Strip-width determines competitive strengths and grain yields of intercrop species in relay intercropping system

“…In many past reports, scientists have reported that soybean suffers from heavy maize shading, especially during the co-growth phase 13 . Maize shading adversely affects the morphology (plant height and stem diameter), physiology (photosynthesis, chlorophyll structure, and concentration), and biochemistry (activities of antioxidants, sucrose, and starch accumulation) of intercropped soybean plants in MSR 28 – 30 . Therefore, intercropped soybean produces a lower yield in MSR as compared to sole soybean yield 13 , 31 .…”

Diethyl Aminoethyl Hexanoate Increase Relay Strip Intercropping Soybean Grain by Optimizing Photosynthesis Aera and Delaying Leaf Senescence

“…The process of flower development into mature pods during the flowering and podding stage determines the number and quality of the soybean pod. Nutrition competition among sourced and sink organs caused flowers and pod abortion and abscission, decreasing soybean pod number and grain yield ( Raza et al, 2020 ). Nitrogen application at the R1 stage increased the soybean grain yield by promoting biomass accumulation during the soybean reproductive growth stage ( Zhou H. et al, 2019 ).…”