The researchers studied how different wheat genotypes respond to water stress during grain filling. They looked at enzymes that help convert sugar to starch in the grains. The enzymes were more active early on but decreased later, especially in the susceptible wheat genotypes. The tolerant wheat genotype maintained enzyme activity better and had less starch reduction under water stress. This led to faster grain filling in the tolerant wheat. The study suggests that enhancing these enzyme activities could help increase starch accumulation in wheat grains, especially under late planting and water scarcity conditions.