J Integr Plant Biol. ›› 1964, Vol. 12 ›› Issue (2): -.

• Research Articles •    

Accumulation and Movement of Starch During Caryopsis Development of the Wheat

S.Y. Hu   

Abstract: The temporary and permanent accumulation of starch and its movements in various parts of the caryopsis of wheat during its development has been investigated. The results are summarized as follows: 1. In the ovary wall starch deposit begins at the time of megaspore mother cell formation, and increases rapidly with the development of ovary and embryo sac. At 7- celled embryo sac stage, the starch content of the ovary wall is at a maximum, but with the further development of embryo sac, the starch content greatly declines. Soon after fertilization, the cells of ovary wall are entirely filled with a heavy starch deposit again, and the starch content is at a second maximum. As the grain matures, the starch content of ovary wall gradually diminishes in association with the collapse of greater part of the parenchymatous cells in the ovary wall. 2. The abundant starch grains are also present in the stigma during the maturation of pistil. Pending the reception of pollen grains the stigma starch deposit is thinning out. During the growth of pollen tube in the stigma tissue, the starch content further diminishes and then completely disappears throughout the entire length of the stigma. The reduction of starch in the stigma is interpretated to mean that starch is converted into soluble sugars and contributes to the nutrition of the growing pollen tubes. 3. The integument and nucellus lack starch in the entire course of seed development. 4. A marked quantity of starch is accumulated in the egg cell and zygote itself and is presumably used in the early development of the proembryo, starch grains then diminish in quantity and disappear in later proembryo. The starch deposit again appears in the differentiating embryo, but in matured embryo, disappears for a second time. Food reserves of protein bodies, not starch, are found within the mature embryo. 5. Starch grains are always present in endosperm tissue during the entire course of its development, but a large quantity of starch is accumulated only in the later stage. The rise of starch in the endosperm coincides strikingly with the decline of the heavy starch deposit in ovary wall during the caryopsis development from proembryo stage to mature grain. It is suggested that the synchronization of the depletion of starch deposit in the ovary wall and its accumulation in the endosperm tissue denotes translocation from the former tissue to the latter. The lack of starch grains in the region of endosperm around the embryo during the course of embryogenesis may be connected with the digestion and absorption for food by the maturing embryo from the adjacent tissue. In brief, there are two major phases of starch accumulation during the period from ovule primordium to mature grain. The first consists a massive temporary deposit in the ovary wall; the second culminates in a large permanent accumulation in the endosperm.

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