Growth Rate, Dry Matter Accumulation, and Partitioning in Soybean (Glycine max L.) in Response to Defoliation under High-Rainfall Conditions

Abstract

The frequency of heavy rains is increasing with climate change in regions that already have high annual rainfall (i.e., Sichuan, China). Crop response under such high-rainfall conditions is to increase dry matter investment in vegetative parts rather than reproductive parts. In the case of soybean, leaf redundancy prevails, which reduces the light transmittance and seed yield. However, moderate defoliation of soybean canopy could reduce leaf redundancy and improve soybean yield, especially under high-rainfall conditions. Therefore, the effects of three defoliation treatments (T1, 15%; T2, 30%; and T3, 45% defoliation from the top of the soybean canopy; defoliation treatments were applied at the pod initiation stage of soybean) on the growth and yield parameters of soybean were evaluated through field experiments in the summer of 2017, 2018, and 2019. All results were compared with nondefoliated soybean plants (CK) under high-rainfall conditions. Compared with CK, treatment T1 significantly (p < 0. 05) improved the light transmittance and photosynthetic rate of soybean. Consequently, the leaf greenness was enhanced by 22%, which delayed the leaf senescence by 13% at physiological maturity. Besides, compared to CK, soybean plants achieved the highest values of crop growth rate in T1, which increased the total dry matter accumulation (by 6%) and its translocation to vegetative parts (by 4%) and reproductive parts (by 8%) at physiological maturity. This improved soybean growth and dry matter partitioning to reproductive parts in T1 enhanced the pod number (by 23%, from 823.8 m−2 in CK to 1012.7 m−2 in T1) and seed number (by 11%, from 1181.4 m−2 in CK to 1311.7 m−2 in T1), whereas the heavy defoliation treatments considerably decreased all measured growth and yield parameters. On average, treatment T1 increased soybean seed yield by 9% (from 2120.2 kg ha−1 in CK to 2318.2 kg ha−1 in T1), while T2 and T3 decreased soybean seed yield by 19% and 33%, respectively, compared to CK. Overall, these findings indicate that the optimum defoliation, i.e., T1 (15% defoliation), can decrease leaf redundancy and increase seed yield by reducing the adverse effects of mutual shading and increasing the dry matter translocation to reproductive parts than vegetative parts in soybean, especially under high-rainfall conditions. Future studies are needed to understand the internal signaling and the molecular mechanism controlling and regulating dry matter production and partitioning in soybean, especially from the pod initiation stage to the physiological maturity stage.

“Canopy fingerprints” for characterizing three-dimensional point cloud data of soybean canopies

“…Splitting these canopies into sub-canopies enables new opportunities for phenomics and further genomic assessment of cultivars. Traditionally, only the labor and time-extensive method of plant component partitioning would come close to this capability, but still lacked the ability for fingerprinting ( Hintz and Albrecht, 1994 ; Raza et al., 2021 ). Sub-canopies paired with their fingerprints have the potential to further explore the unique relationships between certain fingerprint types or clusters with known canopy traits such as branching, leaf size, or leaf angle and their relationships with yield and yield component traits ( Feng et al., 2018 ; Bianchi et al., 2020 ; Moro Rosso et al, 2021 ).…”

The Impact of Foliar Fertilization on the Physiological Parameters, Yield, and Quality Indices of the Soybean Crop

“…During the growing season, assimilation is characterized by three maxima, corresponding to the phenophases of leaf formation and development, flowering, and the accumulation and storage of reserve substances in seeds [48]. Between the variants on which Agro Argentum Forte was applied, significant positive differences were found in both analyzed years, and a higher yield was obtained when fertilization was applied in the initial phase of the pod formation, especially in years that were more favorable to the crop.…”

Compensatory Growth and Physiological Protective Mechanisms of Populus talassica Kom. × Populus euphratica Oliv. in Response to Leaf Damage

“…In Petunia nigra, changes in the photosynthetic capacity vary according to the type of leaf damage, with the removal of leaf margins, removal of leaf tips, and perforation all significantly increasing the photosynthetic capacity; however, the removal of leaf margins is more effective in enhancing the Pn and Gs of the plant than the other two treatments [37]. In Glycine max, Pn also increases significantly after damage treatments, but Ci significantly decreases [38]. However, in Quercus acutissima seedlings with sufficient light and soil nutrients, the Pn significantly decreases after cotyledon damage treatments, and the chlorophyll content only decreases after severe damage [19].…”