Severe drought stress strongly impacts physiological and morphoanatomical traits of soybean cultivars during vegetative stage

Abstract Several studies have investigated soybean response to drought, revealing significant changes in different physiological and anatomical traits. Investigating how plants respond to regulated deficits can help optimize water use efficiency and shed light on their tolerance and sensitivity to water stress at different phenological stages. Thus, this study aimed to assess the effect of water stress during the vegetative stages on the morphophysiological and water status characteristics of soybean cultivar. The experiment was conducted in a greenhouse at the State University of Maranhão. A completely randomized design with four irrigation levels: 100% field capacity (FC) (control), 75% FC, 50% FC, and 25% FC, and 20 replicates were used. Growth variables, physiological parameters, water-related parameters, and root, stem, and leaf anatomy were evaluated. Interaction was observed between water levels and assessment times for plant height and stem diameter growth rates. There was a significant reduction in gas exchange over time, with the greatest decline at 81 days after planting (DAP). The 25% FC treatment had the most pronounced effect on the photosynthetic CO 2 assimilation ( A ), stomatal conductance ( g s ), transpiration ( E ), and carboxylation efficiency (CE), with reductions of 55, 72, 53, and 60%, respectively, compared to the control, at 80 DAP. Anatomical analysis revealed adaptations in the 25% FC treatment, characterized by increased stem sclerenchyma thickness and smaller root xylem vessel diameter. Plants in the 75% FC treatment showed similar responses to the control, demonstrating that this water regime did not compromise the growth and development of BRS Tracajá soybean plants.