Maize Kernel Moisture at Physiological Maturity as Affected by the Source–Sink Relationship during Grain Filling

Abstract

ABSTRACTA wide range of values reported in the literature has precluded the use of grain moisture (GM) as an estimate of physiological maturity (PM) in maize (Zea mays L.). The reason for this variability in GM values remains unclear. Previous evidence suggests that the source–sink ratio could affect the dynamics of kernel water relations during grain filling and thus, GM at PM. To test this possibility, treatments were applied to manipulate the reproductive sink capacity or the assimilate availability during grain filling. Kernel dry weight, water content, and the dry weight to water content (D–W) ratio, were monitored throughout grain filling. A bilinear model relating dry weight and GM was used to estimate GM at PM for each treatment. Severely restricting source capacity during grain filling increased GM at PM. When the source capacity per kernel during grain filling was increased, however, GM at PM was not affected. A single model (r2 = 0.99, p < 0.001) described the relationship between relative dry weight and GM for all hybrids and treatments without source reduction during grain filling. The estimated value of GM at PM for this model was 34.9%. These results suggest that calculating GM late in grain filling can provide a reliable estimate of PM when the source capacity has not been severely restricted. A value of 35% moisture would be adequate in these situations. The D–W ratio of developing kernels was similar across all source–sink treatments until PM. Premature cessation of grain filling caused by defoliation increased the D–W ratio as the kernels continued to desiccate.