Soil water deficit suppresses development of maize ear by altering metabolism and photosynthesis

Abstract Drought is one of the most detrimental crop stresses that substantially impede maize productivity globally. This study subjected maize plants at the vegetative/generative transition phase to three soil water treatments (WW, well-watered, soil moisture at 80 ± 5%; WD1, water-deficit 1, soil moisture at 60 ± 5%; WD2, water-deficit 2, soil moisture at 45 ± 5%) to investigate the effect of drought on young ear development. Subsequently, the differentiation and size of ears were evaluated, along with carbohydrates quantification and RNA-sequencing of the ear. The maize leaf photosynthesis and plant growth parameters were also measured. The results showed that WD1 and WD2 decreased the total biomass by 54.3 % and 61.4 % at 54 days after emergence (DAE). Compared to other plant organs, the ear and leaf contributed the most to the biomass decrease. The diameter of ears under WD1 and WD2 were significantly decreased by 30.0 % and 50.0 %, respectively, at 54 DAE. Interestingly, transcriptome analysis of the ears at 54 DAE indicated that the differentially expressed genes in WD2 mainly participated in starch and sucrose metabolism. Furthermore, the starch, glucose, and sucrose contents of WD2 were significantly reduced. Notably, WD2 significantly decreased the leaf photosynthetic capacity. Meanwhile, WD1 and WD2 significantly reduced the net assimilation rate and enhanced the specific leaf weight at 44 DAE. However, no change was found at 54 DAE. Finally, WD1 and WD2 decreased the length and diameter of the ear at harvest, especially the export proportion and conversion proportion of leaves during the grain filling stage. In summary, soil WD decreases assimilate accumulation in maize plants and metabolism in young ears, hence suppressing ear development during the vegetative/generative transition phase.