Grain filling leads to backflow of surplus water in maize grain via the xylem to the cob and plant

Abstract

The rapid dehydration rate of maize grain is one of the main characteristics of cultivar selection of mechanical grain harvest, but the dominant driving force and mechanism of grain dehydration before physiological maturity remains disputable and obscure, respectively. This study found that, from grain formation to 5-10 days before physiological maturity of early and middle maturity maize cultivars, the main driving force of grain dehydration is filling and then converts to surface evaporation, by comparing the grain moisture content and dehydration rate between grain coated treatment and control. In the dye movement experiment, xylem-mobile dye movement into grain through pedicel xylem was observed during grain formation period, and declined and gradually not observed after grain formation. Xylem-mobile dye movement out of ear via cob, ear-pedicel and stem xylem was observed after grain formation. In addition, from grain formation to physiological maturity, there was a very significant positive correlation between grain filling rate and dehydration rate. According to these results, it is proposed here that in the grain dehydration phase driven by filling, the surplus water in grain flows back to cob via pedicel xylem, and some of it flows back to plant via cob and ear-pedicel xylem. HighlightThe surplus water in grain driven by grain filling flows back to the cob and plant for recyclingvia the xylem during the development of maize grain.