Ultrastructural Localization Of ATPase Activity During The Anther Development Of Lettuce (Lattuce Sativa L.)

ATPase distributes widely in cells, and it takes part in all kinds of physiological activities of cells. Sexual reproduction of higher plants is a complex process including a series of delicate developmental processes of sexual organs and cells, and some special time and special interactions between male and female tissues. Until now the distributional characters and physiological functions of ATPase are not clear during anther development. In this study, we systemically investigated the distributional characters and physiological function of ATPase during the anther development of lettuce (Lattuce sativa L.) with ATPase-lead nitrate depositional method. The results are as follows:During anther early development, only few ATPase precipitates located in small vacuoles and the nucleus of microspore mother cell and tetrad microspore. There were still few ATPase precipitates in the cytoplasm of young microspore just released from the tetrad, but abundant ones specially accumulated in the germ pore, and some ones began locating on the surface of extine. When some small vacuoles appeared in the cytoplasm, ATPase precipitates increased in the nucleus, small vacuoles and cytoplasm of microspore. Meanwhile the microspore began to synthesize its intine. and lots of ATPase accumulated in intine suggesting it might play an important part in this process. At the same time, some vacuoles which contained bigger ATPase precipitates fused together constantly and finally became a big central vacuole, in which ATPase precipitates increased obviously and some formed into flocky precipitate. On the contrary, ATPase precipitates decreased in the cytoplasm and nucleus except in the intine and the germ pores where numerous ATPase precipitates were located. There were many tiny precipitates from tapetum accumulating on the surface of sexine as well. As a big vacuole appeared in the microspore, polarity of microspore was created. The mitosis of polar microspore formed a 2-cellular pollen grain. ATPase precipitates were more in both nuclei of vegetative cell and generative cell but less in the cytoplasm. When the generative cell detached from the intine of the vegetative cell, abundant ATPase precipitates specially accumulated in the place where the wall of generative cell and the intine wall of vegetative cell connected. With generative cell detaching, the precipitates in it kept decreasing. When the generative cell completely suspended in the cytoplasm of the vegetative cell, the precipitates on the wall of the generative cell entirely disappeared. The mature pollen of lettuce was 3-cellular pollen, some ATPase precipitates only located in the cytoplasm of the vegetative cell, and the nuclei of vegetative cell and generative cell. But most of ones were mainly distributed in the intine, the surface of sexine and the prominencys of sexine.The anther wall of lettuce was composed of four layers of cells, epidermis, endothecium, middle layer and tapetum. During anther early development, epidermis, endothecium, middle layer became high vacuolization, and had few ATPase precipitates in their cytoplasm all along, while most of precipitates mainly located on their plasma membrane, suggesting that the function of the three layers' cells was transportation of nutriment. The quantity of ATPase precipitates of tapetal cells changed obviously: during early tetrad stage the ATPase precipitates in the cytoplasm evidently increased, and the number of the precipitates reached the peak in early microspore stage. And many tiny ATPase precipitates increased in the locule of anther at this stage. Furthermore, the inner surface of tapetum accumulated more ATPase preci- pitates than the outer surface. The polar distributional character indicated that the primary function of tapetum was to transport the nutrition materiel into locule.During the anther development, many ATPase precipitates located in the nucleus, cytoplasm, and plasma membrane of parenchymaic cells of vascular bundle, but few in cell walls and cellular gap. However, there were many ATPase precipitates accumulated in cell walls and cellular gap of connective tissue, and so was the plasma membrane and vacuole membrane, suggesting that the nutrition materiel ship out vascular bundle mostly suing symplast approach, while apoplast approach might not very active. But when the nutrition materiel was transported in the connective tissue, both approaches might be used effectively.The distributional character and physiological function of ATPase during the anther development of lettuce were discussed.