The effect of drought stress on nodulation, plant growth, and nitrogen fixation in soybean during early plant growth

Abstract

Soybean [Glycine max (L.) Merr.] is one of the most important grain legume crops in the world. Soybean forms a symbiotic relationship with the nitrogen-fixing rhizobia bacteria that reside in root nodules and fix atmospheric nitrogen. Most of the soybean's nitrogen demand is derived from symbiotic nitrogen fixation (SNF). Drought is becoming a major threat to crop production in the world. Legumes are sensitive to drought stress, and drought can negatively affect SNF, grain yield, and seed protein production. The effect of drought stress on soybean growth, morphological traits, nodulation, water use efficiency, and SNF, particularly during early plant growth, remains poorly characterized. We hypothesized that early-onset drought stress can negatively affect nodulation, plant growth, and SNF in soybean during the vegetative growth stages. To test this hypothesis, a controlled-environment study was conducted using soybean plants grown in pots, where plants were subjected to moderate drought stress (40% field capacity) and well-watered (80% field capacity) from seeding until the flowering stage. Drought stress significantly reduced the nodule number and nodule dry weight, root and shoot biomass, shoot total nitrogen content, shoot carbon to nitrogen ratio, and shoot total fixed nitrogen compared to the well-watered control.Conversely, root-to-shoot ratio and shoot nitrogen concentration were higher under drought stress compared to well-watered conditions. These findings enhance our understanding of adverse impacts of drought in the early growth stage of soybean while suggesting that reduced total nitrogen assimilation during the vegetative phase can lead to less nitrogen reserves available for translocating at the seed filling stages for seed protein production. This information should aid in generating drought-tolerant soybean cultivars.

Ability of nitrogen-fixing bacteria to alleviate drought stress in cowpea varies depending on the origin of the inoculated strain

“…This indicates that root infection and the onset of nodulation are affected by drought stress. In contrast, plants inoculated with BR 3299 maintained the same nodule dry mass in both the well-watered and water-restricted regimes (Table 2), suggesting that plants inoculated with BR 3299 compensated for stress by increasing the mass of existing nodules (Lumactud et al 2022). Interestingly, plants inoculated with BR 3299 showed a smaller number and mass of nodules; however, they were the only plants that did not show a decrease in nodulation under water restriction treatment.…”

“…Cowpea production in Brazil is primarily concentrated in the semi-arid regions of the northeast. Although cowpeas are considered drought-tolerant, water de cits during the early vegetative stages can negatively affect their morphological and physiological traits, ultimately affecting biological nitrogen xation (BNF) and grain yield (Munjonji et al 2018;Ayalew and Yoseph 2022;Lumactud et al 2022).…”

“…Cowpea production in Brazil is primarily concentrated in the semi-arid regions of the northeast. Although cowpeas are considered drought-tolerant, water de cits during the early vegetative stages can negatively affect their morphological and physiological traits, ultimately affecting biological nitrogen xation (BNF) and grain yield (Munjonji et al 2018;Ayalew and Yoseph 2022;Lumactud et al 2022).Plant growth-promoting rhizobacteria (PGPR) offer a promising biotechnological approach for mitigating the effects of abiotic stress on various crops (Bittencourt et al 2023;Cao et al 2023). Microbial communities sourced from speci c environments, such as semi-arid regions, adapted to drought conditions, may exhibit enhanced effectiveness in assisting plants to cope with water de cits (Shirinbayan et al 2019;Shet and Garg 2022;Braga et al 2022).…”

Water deficit as a trigger to immature soybean pod opening

“…Besides that, based on the hypothesis that water deficit has strong negative influences on productivity and on important morphological, physiological and biochemical traits of soybean plants (Cotrim et al, 2021; Farooq et al, 2012; Lumactud et al, 2022; Veas et al, 2022), the occurrence of immature pod opening may be one of the dysfunctions caused by the decrease in cell turgor. Therefore, this study aimed at evaluating, phenotypically, the opening of immature pods of soybean genotypes grown in two distinct seasons, when submitted to water deficit.…”

Genotypic stability in root system architecture and aboveground biomass revealed diverse adaptability of peanut (Arachis hypogaea L.) to moderate water deficit

“…Plants change biomass partitioning between above‐ and below‐ground structures to cope with stress in order to balance the relationship between potential water loss from transpiration and water uptake from roots (Voss‐Fels et al, 2018). It is widely documented that an increased root‐to‐shoot ratio can occur as a plant response to the water deficit stress (Correa et al, 2019; Griffiths & Paul, 2017; Lumactud et al, 2023). This partitioning shift generally acclimates the plant hydraulic system to water deficit by reducing the canopy water loss and increasing the accessibility of roots to water resources (Mathew et al, 2018).…”