Grain water weight dynamics and their relationships with grain filling in maize

Grain filling and dehydration are synchronous but opposing processes in maize that occur during the process of grain development; large grains are often poorly dehydrated. The theoretical feasibility of coordinating grain filling and dehydration remains unclear. Here, we used an agronomic indicator, grain water weight, to analyze the relationship between grain filling and dehydration. Data from 61 maize cultivars and 8 sowing dates × 2 years were analyzed to elucidate the inherent water dynamics during grain filling. The results revealed four stages of water dynamics following grain filling: absorption, platform, pre-maturity dehydration, and post-maturity drying. Grains reached the maximum water weight and remained stable in the platform stage, which coincided with the rapid filling period and the maximum filling rate. Greater water weight at the platform stage was associated with a larger final grain weight, which indicates that the indicator can be considered as the criterion for high grain weight or yield potential. However, net water loss did not begin until the end of the platform stage. Water loss in the third stage was related to moisture content at maturity, and more and faster water loss means lower moisture content at maturity, so it may be a potential stage for targeted selection of grain dehydration characteristics. Overall, yield potential and grain dehydration appeared to be determined by different stages, and there may be no contradiction in directional selection of cultivars with both high yield potential and low moisture content at distinct grain-filling stages.