Leaf structure and ultrastructure changes induced by heat stress and drought during seed filling in field-grown soybean and their relationship with grain yield

Abstract Studies focusing on terminal drought combined with heat impacts plants of agronomic value remain scarce, and even less under field conditions. The objective this study was to investigate leaf structural ultrastructural changes induced by stress (HS) (DS) during seed filling their relationship physiological variables yield determination. Two soybean cultivars were grown in During four treatments applied, including a control (without manipulation, at ambient temperature capacity), HS (episodes exceeding 32°C for 6 h d-1) 21-d, DS (20% capacity soil water content) 35-d, HS×DS. Drought principally reduced area, whereas decreased thickness, possible as acclimation strategies, but also irreversible reducing CO2 assimilation sites. Both stresses damaged the outer inner membranes chloroplasts, causing swollen chloroplasts accumulation plastoglobules, loss chlorophyll content, negatively affecting fluorescence. Thus, performance integrity photosynthetic machinery reduced. Through morpho-functional perspective holistic multiscale approach, our results provide evidence photosynthesis impairment drops stressful conditions which associated (particularly level chloroplasts) modifications leaves.