鼠尾藻(Sargassum thunbergii)有性生殖过程与育苗

采用室内培养和野外实地观测的方法,研究了鼠尾藻的生长发育和有性生殖过程,并在此基础上进行了有性生殖人工育苗实验。结果表明,鼠尾藻在海水温度高于22℃时,生殖托开始发育,海水温度超过23℃以后,生殖托的生长速度加快,海水温度超过24℃时,生殖托生长速度最快并迅速成熟,在海水温度达到26℃时,观察到了卵的集中排放挂托现象。鼠尾藻卵的排放较为齐整且有一定的先后顺序,生殖托基部的卵最先排出,中部次之,最后是顶部,雄托排精时间要稍晚于雌托排卵时间。受精卵大约在受精1h后进行第一次细胞分裂,分裂面与长轴垂直,大约2h后进行第二次分裂,下端细胞的分裂面平行于第一次分裂方向,而上端细胞的分裂面则垂直,随后大约每2—4h细胞分裂一次。从卵挂托到幼胚脱落一般需要24—48h。观察发现,生殖窝不仅存在于生殖托上,在部分生殖枝上也有分布。在鼠尾藻的人工育苗的实验中,胚苗在苗帘上的生长状态良好。

THE SEXUAL REPRODUCTION OF SARGASSUM THUNBERGII AND ITS APPLICATION IN SEEDLING BREEDING

The growth, development, and sexual reproduction of Sargassum thunbergii were studied in Qingdao, Shandong Peninsula, China, in the spring and summer of 2006 by indoor cultivating and observing on the local tidal sites. The results showed that both the growth in algal length and receptacle development depended on seawater temperature. The algal length increased quickly at seawater temperature of 23°C. The receptacles were visible and started to develop at 22°C. The receptacles grew and developed fast at 24°C and higher. Eggs were released off mature female receptacles at about 26°C. The eggs attached to the surface of female receptacles, and were laid in turn from bottom to top of the receptacles. More than 400 eggs were laid from a single female receptacle and a female plant could produce about 5 million eggs. Sperms were released from the male receptacles after the eggs were laid. The zygote began its first division at about 1 hour post-fertilization, the division section was vertical to the major axis, and 2 same-sized cells were produced. About 2 hours after the first cell division, cell split again. The division section of the down cell paralleled to the first division direction for producing a large cell and a small cell. The small cell would gradually developed into rhizoids. The division of the upper cell was slightly later than that of the down cell, and the division section was vertical to that of the down cell. Subsequently, in every 2-4 hours the cell would divide once, the cells split further and developed to embryo. It took about 24-48 hours from the eggs shedding to embryo formation and detaching from the female receptacles. Conceptacles were found in some reproductive branches with eggs shedding, which showed that the reproductive branches played some functions of reproduction too.

Additional to the study of S. thunbergii sexual reproduction, seedling breeding was conducted. The seedling length of S. thunbergiiincreased to 0.3-0.4mm in average within 18 days, and the seedlings grew well with a coarse surface and darkened color. It indicated that the seedling breeding via sexual reproduction for S. thunbergii was feasible.