The Distribution Of Calcium In Lycium Barbarum L. During The Development Of Anther

Calcium is an indispensable element during plant growth and development, which not only functions as a signal molecule but also a nutritious element with many important physiological functions. Sexual reproduction of higher plants is a very complex process including a series of delicate differentiations of sexual organs and cells. Ca2+ is of importance in the process of sexual reproduction of higher plants, and it has been shown to play a number of roles. But past studies mostly focused on: 1. the effects of calcium on pollen germination and tube growth in vitro; 2. the relation between the calcium distribution on the tip of pollen tube and the growth of pollen tube; 3. the calcium distribution in the ovules and embryo sacs before and after fertilization. Nevertheless, the studies about calcium distribution and its functions during anther development are a few. So we used potassium antimonate to precipitate Ca2+ to investigate the calcium distribution during anther development of Lycium barbarum L. The results were as follows:Before the stage of microspore mother cell, few calcium-induced precipitates were found in young anthers. Then some calcium precipitates appeared in the surface of callus wall of microspore mother cells. Many small precipitates accumulated in chromosomes of microspore mother cells during meiosis. After the meiosis of microspore mother cells, calcium precipitates were increased in the cytoplasm and callus wall of early microspores, and then accumulated in pollen wall, especially in germ-pores. With the microspore development, abundant of calcium precipitates were accumulated between the sexine and enxine of exine of pollen wall. At the late microspore stage, a big vacuole formed and the nucleus was pushed to peripheral region. Calcium precipitates in the cytoplasm and nucleus of microspore decreased sharply, but many were still in the germ-pores. After microspore mitosis, the big vacuole was decomposed into many small vacuoles, and till disappeared completely. Many calcium precipitates again appeared in the cytoplasm, nucleus and small vacuoles of vegetative cell of 2-cellular pollen. As pollen maturating, the cytoplasm of vegetative cell became densely and storage materials like starches accumulated inside the pollen grains. Many small vesicles with calcium precipitates appeared again in the cytoplasm of vegetative cell. After pollen grains maturing completely, there were more lipid drops and a few starches in the pollen grains, and only few calcium precipitates were in pollen.The anther wall of Lycium barbarum L. was composed of four layers of cells: epidermis, endothecium, middle layer and tapetum. During microspore development, epidermis, endothecium, middle layer became high vacuolization, and had a few calcium precipitates in their cytoplasm. The quantity of calcium precipitates in tapetal cells changed obviously. The tapetum cells were marked off connective tapetum derived from the cells of the connective and wall tapetum from the parietal layer. Two kinds of tapetum displayed some differences: more calcium precipitates were in connective tapetum than in parietal tapetum. At the stage of microspore mother cell, some calcium precipitates appeared on the inner surface of tapetum. During tetrad stage calcium precipitates in the tapetal cytoplasm evidently increased, and the number of the precipitates in locule reached the peak. During the vacuolation of microspore, the connective tapetum degenerated, which was earlier than parietal tapetum. Its decomposed substance and calcium precipitates moved into locule and joined the development of pollen. .