Cell Growth and Nucleic Acids in the Pollen of Rhoeo Discolor

Abstract

1. A cytoplasmic basophily, which is removed when cells are treated with a ribonuclease enzyme, has been used as a means of identifying ribose nucleic acids and of following their distribution in the cells of the anthers of Rhoeo, and to a lesser extent in the pistil of the flower. Rapid cell growth is invariably accompanied by large amounts of ribonucleic acid in the cytoplasm and heavy deposits of chromatin in nuclei. 2. In young anthers the cytoplasm of both tapetal and sporogenous tissues is extremely rich in ribonucleic acid. As the pollen mother cells prepare for the meiotic divisions, the ribonucleic acid disappears from the cytoplasm, presumably being passed into the nucleus and changed into desoxyribose nucleic acid (chromatin). Initially the cytoplasm of microspores is devoid of basophilic material, but as they grow into mature pollen grains large amounts of ribonucleic acids accumulate in the cytoplasm. 3. The growth of tapetal cells is accompanied by one or more endomitotic nuclear division cycles. The tapetal cells, which are rich in cytoplasmic nucleic acid at the time of cytolysis, are the source of the ribonucleic acid which accumulates in the maturing pollen grains. 4. There is a similarity between microspore growth at the expense of tapetal cells and growth of oocytes in animals through the agency of nurse cells. Large amounts of ribonucleic acid are stored in mature pollen grains and used in the extremely rapid synthesis of new materials which accompanies pollen tube growth.