grainfilling

Grainfilling is a developmental phase in cereal crops and some other grain-producing species that occurs after flowering, during which kernels accumulate most of their dry matter. In this period, the endosperm tissue becomes the primary storage tissue, and storage compounds such as starch, storage proteins, and lipids are synthesized and deposited. The rate and duration of grainfilling largely determine final grain weight and overall grain quality.

The process involves coordinated physiological and biochemical events. Carbohydrate and nitrogen assimilates are transported from source organs (primarily leaves) to the grain sink. Within the grain, starch biosynthesis proceeds through enzymes such as starch synthases, branching enzymes, and AGPase, while protein accumulation contributes to kernel composition. Endosperm cell division and expansion contribute to kernel size in early grainfilling, followed by rapid storage compound accumulation as the grain matures.

Environmental and genetic factors strongly influence grainfilling. Temperature, water availability, and nutrient supply affect both the rate and duration of filling. High temperatures can shorten the filling period and reduce starch deposition, while drought can limit assimilate supply. Nitrogen availability can alter grain protein concentration. Genotypic differences determine kernel filling rate, duration, and tolerances to stress, making grainfilling a key target in breeding programs aimed at improving yield and grain quality.

Practical implications include optimizing crop management to minimize stress during grainfilling, such as timely irrigation or rainfall management, balanced fertilization, and strategic planting densities. Assessments of grainfilling performance often focus on final kernel weight, grain filling rate, and the duration of the filling phase.