Pathway of pollen tube growth and the duration of different phases of fertilization process in wheat

Chinese. 应用常规石蜡切片和荧光显微镜技术，对小麦花粉管生长途径及受精过程相应时间进行了研究。结果表明，授粉后，花粉随即萌发，2个精子进入花粉管，营养核留在花粉粒内，不久解体。花粉管进入羽毛状柱头分支结构的细胞间隙，继续生长于花柱基部至子房顶部的引导组织的细胞间隙内。随后穿过子房壁，在子房壁与外珠被之间的缝隙中向珠孔方向生长。白花粉萌发至花粉管长入珠孔大约需要1h。白花粉萌发并到达柱头分支结构中，花粉管均具明显的绿色荧光；但在引导组织区以及子房壁与外珠被之间生长的花粉管几乎看不到荧光。授粉后1h花粉管经珠孔及珠心表皮细胞间隙进入1个助细胞，并释放精子。授粉后2―6h精卵融合，授粉后16h合子第一次分裂。授粉后2，3h精子与极核融合，授粉后4h初生胚乳核第一次分裂。授粉后2―16h，即精卵融合至合子分裂前为花粉管通道法转化合适的时间，采用花柱横切滴加法转入外源DNA。

English. Pathway of pollen tube growth and the duration of different phases of fertilization process were studied by paraffin sections and fluorescence microscope technique in three cuhivars of wheat. The results are as follows： Pollen grains germinate soon after pollination. Two sperms enter pollen tube, leaving vegetative nucleus, which degenerates in pollen soon. Pollen tubes go into intercellular space of branched structure of penniform stigma, then go through the intercellular space of transmitting tissue from the base of style to the top of ovary, after that penetrate ovary wall and grow towards micropyle through the gap between ovary wall and primine. It is about 1 h from germination to the arrival at micropyle. The pollen tubes show strong green fluorescence from germination to the arrival at the branched structure of penniform stigma, little fluorescence displays in the pollen tubes, which are in transmitting tissue and the gap between ovary wall and primine. One hour after pollination, pollen tube goes through the intercellular space of nucellar epidermis and enters one of the synergids, releases two sperms. Two to six hours after pollination, egg-sperm fusion occurs. Sixteen hours after pollination, zygocyte begins to mitosis. The fusion of sperm and two polar nuclei occurs. Two to three hours after pollination, and primary endosperm nucleus begins to divide 4h after pollination. Thus,2 16 h after pollination, which is the duration from egg-sperm fusion to the beginning of zygocyte mitosis, should be the time for exogenous DNA transformation by the method of pollen-tube pathway. The operation is to cut style transversely and drop exogenous DNA on the transection.