Studies on the Developmental Physiology in Rice Pollen : II. Relation between the amino acid metabolism and the structural changes in pollens

Abstract

The relation between the changes of amino acid metabolism and the structural alteration with special reference to the behavior of the vegetative and generative nucleus during pollen development were studied. At the one nuclear period no distinct difference was found in amino acid composition between anthers and other plant tissues and organs. In binuclear period in which a microspore nucleus divided into two nuclei, a vegetative nucleus and a generative one, the proline content comes to higher than that of other amino acids in anthers. At the middle of binuclear period proline was found to occupy about 20% of all amino acid content, indicating that the special feature of amino acid metabolism in pollen begins under the occurrence of a vegetative and a generative nucleus. At the beginning of trinuclear period having one vegetative nucleus and two sperm nuclei, proline was found to reach an amazing high content as like 50% of total amino acids in anthers. Thus accumulated synthesis of proline, known as the characteristic of amino acid metabolism in pollen, appears established at the trinuclear period. Activity of nuclei in pollen was examined by the size of nucleolus after acetocarmine staining since it has been considered as an indicator of the physiological activity of nucleus. At the one nuclear period, a large nucleolus just like as that of meristematic cells was found in a microspore nucleus. In the time when a microspore nucleus divided into a vegetative and generative nucleus, a nucleolus of the former was larger than that of the latter. With the occurrence of two sperm nuclei, the size of a nucleolus in vegetative nucleus began to decrease and the configuration of nucleus was obscure and its nucleolus disappeared in the day before flowering. On the contrary, nucleoli of two sperm nuclei derived from a generative one, were large and clear since then. On the basis of these results, it was assumed that the establishment of the special feature of amino acid metabolism in pollens and the occurrence of generative or sperm nucleus are correlated each other in time, and the accumulated production of proline may be regulated by the sperm nuclei, judging from the behavior of nucleolus