甘蓝型油菜授粉前后珠孔和胚囊中钙分布的超微细胞化学定位

ULTRACYTOCHEMICAL LOCALIZATION OF CALCIUM IN MICROPYLE AND EMBRYO SAC OF BRASSICA NAPUS BEFORE AND AFTER POLLINATION

用焦锑酸盐沉淀法对甘蓝型油菜（ＢｒａｓｉｃａｎａｐｕｓＬ．）授粉前后珠孔和胚囊中的钙进行了超微细胞化学定位。Ｘ射线能谱微区定性分析（ＥＤＸＡ）表明前法所得沉淀确系焦锑酸钙。同时利用图像处理系统对胚囊成员细胞中钙沉淀颗粒的体密度和大小进行了定量分析。结果显示，授粉前后内、外珠孔处钙沉淀明显较珠被其它部位为多，钙主要分布在细胞壁和胞间基质等质外体系统中。授粉前２个助细胞中均含有较其它细胞为多的钙沉淀，约为卵细胞的２５倍，中央细胞的１９倍；但沉淀颗粒的直径仅为它们的２／３左右。助细胞中含钙最多的部位是丝状器和细胞核。授粉后１对姊妹助细胞均明显退化，钙含量显著增高，约为授粉前的２４倍；钙颗粒明显减小，不足授粉前的１／３。讨论了钙的分布与助细胞的退化及其功能的关系。

Potassiam antimonate was used to localize Ca^2+ in the micropyle and embryo sac of Brassica napus L. before and after pollination. To identify the nature of the pyroantimonate deposits, energydispersive X-ray microanalysis (EDXA) was employed and the deposits were proved to contain calcium pyroantimonate. Image processing system was employed to measure the volume density and the diameter of the deposits. Before and after pollination, calcium was more abundant in the exostome and endostome as compared with the other regions of the integuments, and was concentrated at the apoplast system, i.e. the intercellular matrix of the micropyle canal and the cell wall. Before pollination, each of the two sister synergids accumulated more calcium than the other embryo sac cells. Although the mean diameter of the deposits in the synergid was only twothirds as that in the egg cell and central cell, the volume density of the deposits in the synergid was about 2.5 times and 1.9 times as that in the egg cell and the central cell respectively. The filiform apparatus and the nucleus had the most abundant calcium within a synergid. After pollination both sister synergids degenerated conspicuously and were characterized by much more deposited calcium (about 2.4 times more than before); and the diameter of the deposits decreased dramatically, which was less than one-third as before. The relationship between calcium distribution and synergid degeneration as well as its functions was discussed.