RE-CLASSIFICATION OF DEVELOPMENTAL STAGE OF WHEAT-GRAIN

Developmental stages of wheat seed that were identified easily have been classified by two different ways; one based on the endosperm development (six stages of watery, milky, soft dough, hard dough, ripe, and dead ripe) and the other based mainly on the embryo development (five stages of I to V). We examined these two types of the developmental stages by observing embryo and endosperm development, and appearance of seeds. Since we find characteristic developmental stages of wheat seed in respects of dry weight increase and morphological development of embryo and endosperm, we propose the following six development stages. At stage 1 (from fertilization to days post anthesis (DPA) 5), the embryo is globular and do not vet differentiate. The endosperm grows most rapidly. The seeds are white green and less than 4 mmin length. At stage 2 (from DPA 5 to 10), the embryo differentiates into embryo axis and scutellum. The endosperm still grows rapidly. At stage 3 (from DPA 10 to 15), the scutellum elongate. Dry weight of the seeds increases most rapidly. The endosperm becomes milky. At stage 4 (from DPA 15 to 20), the primary leaf, root and coleoptile differentiate in the embryo axis. The size of the endosperm and consequently the size of the seed reach their maximum. The seeds become fresh green. At stage 5 (from DPA 20 to 30), the embryo differentiates further and its dry weight increases most rapidly. The reserve accumulation in the endosperm shows the second peak. The endosperm has a soft dough consistency. The seeds show yellowish part. At stage 6 (from DPA 30 to 50), the seeds desiccate and turn brown. The stages of hard dough, ripe, and dead ripe are included in the stage 6.