Re-classification of developmental stage of wheat grain.

Abstract

Developmental stages of wheat seed that were identified easil)- have been classfied by two different ways'; one based on the endosperm development (six stagcs 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 types5 of the developmental stages by obscrving embryo and endosperm development, and appearance of seeds. Since lve find charactoristic developmental stages of wheat seed in res.pects.' of dry weight increase and morpho]ogical development of embryo and en-dosperm, we propose the following six development stages. At stage I (from fcrtilization to days post anthesis (DPA) 5), the embryo is globular and do not yet differentiate. The endosperm grows most rapidly. Thc seeds are lvhite green and less than I 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 coleoptilo 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 res.erve accumulation in the endosperm shows the socond peak. The endosperm has a soft dough consistency. The s.eeds show yellolvish part. At stage 6 (from DPA 30 to 50). the seeds desiccate and turn brown. The stages of hard dough, ripe, and dcad ripe are included in the stago 6.