[The distribution of calcium in the stigma and style of tobacco during pollen germination and tube growth].
After pollen grains of tobacco landed on stigma they begin to hydrate and form many small vesicles containing some calcium grains in cytoplasm. The calcium stored in pollen wall is released into tectum of stigma to make a calcium-rich environment. When a pollen tube penetrates the tectum and grows between stigma cells, numerous calcium precipitates appear in the tip tube wall. The length of style of tobacco is 4 cm, and the pollen tube need take 44 h to reach the ovary. The style was artificially divided into 4 stages and each 1 cm respectively. There were only a few of calcium precipitates in the transmitting tissue of style from anthesis to 11 h after pollination. A calcium gradient in the transmitting tissue of style was formed at 22 h after pollination: only a few calcium precipitates found in the transmitting tissue of the style under stigma and at stage 1, 2 and 3, and many of them were located in the transmitting tissue of style near ovary (stage 4). When the flowers were emasculated and unpollinated at 1 d after anthesis, no calcium gradient in the transmitting tissue of style could be identified because some precipitates were also accumulated in the transmitting tissue at stage 1. When a flower without pollination was kept for 3 d, some calcium precipitates were formed in the cells of stigma, and the cells of the whole transmitting tissue contained the same quantity of calcium precipitates. To check the ability of pollen to germinate and grow in a low calcium environment, pollen grains were cultured in a medium containing 0-0.1% CaCl(2).2H(2)O. The result of in vitro assay confirmed that tobacco pollen can germinate and the pollen tube can grow in an environment with a very low concentration of calcium, which may be similar to the environment in the stigma. A few calcium precipitates were accumulated in stigma and upper transmitting tissue of tobacco to make a calcium gradient in the style. If the calcium in the style at 1 cm increases it will be increased more at 4 cm, and more in ovules, and more in synergid cells to keep the calcium gradient. When the emasculated flowers were not pollinated for 3 days the calcium in upper transmitting tissue evidently increases. The calcium in style is abundant in all plants, but the distribution of calcium in style is different between different plant species. For this difference, it may differ from types of style, and in the plants with short style the calcium gradient in the style is too small to be detected. But for tobacco with style 4 cm long, the gradient can be identified using antimonate method.
Xie
Chao-Tian
CT
The Key Laboratory of Education Ministry for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, China.
Qiu
Yi-Lan
YL
Ge
Li-Li
LL
Chen
Su-Hong
SH
Tian
Hui-Qiao
HQ
D002118:Calcium / Q000378:metabolism*; D035264:Flowers / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D011058:Pollen / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D053205:Pollen Tube / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D014026:Nicotiana / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure
D002118:Calcium