Developmental and Histochemical Studies of the Ovules of Nicotiana rustica L.

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Abstract
The developmental and histochemical aspects of the ovules of N. rustica L. were investigated from the time of anthesis to the maturity of seeds. Pollination takes place on the day of anthesis and fertilization 1 day later. The endosperm development is ab initio cellular, and embryogeny conforms to the Solanad type. The seeds are albuminous, and a major portion of the seed is occupied by an embryo surrounded by a few layers of endosperm and the seed coat. Histochemical studies show that before pollination, the integument contains numerous protein bodies, but at maturity the seed coat is devoid of proteins, and the embryo and endosperm are replete with proteins. Starch is absent in the integumentary cells of ovules from unpollinated ovaries and is present in small quantities in the central cell of the embryo sac. Immediately after pollination and fertilization the situation is reversed; integument cells now contain numerous starch grains. Starch was not observed in the embryo or endosperm at any stage of development. During the development of the embryo and endosperm, starch is gradually mobilized from the integument and provides energy for the embryo and endosperm. The zygote stains densely for RNA and proteins. It lacks starch grains and only a small portion of the DNA stains with Feulgen. A very interesting feature in the egg cytoplasm is the presence of 2 highly RNA-positive bodies which, after fertilization, increase in number and persist until the 4-celled stage of the proembryo. The suspensor cells at the globular stage of the proembryo stain poorly for histones, but they have a higher concentration of total protein than the embryo proper.

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