【摘要】 作者观察了江蓠幼苗的早期发育过程,根据发育过程中的形态特征,将其划分成四个发育时期:(1)孢子初分时期;(2)“半球状体”时期;(3)盘状体时期;(4)幼苗时期。三个不同的发育途径:(1)具有盘状体的幼苗发育;(2)不具有盘状体的幼苗发育;(3)幼苗的畸形发育,和出现两种幼苗。并讨论了盘状体的“愈合”现象和江蓠幼苗在发育过程中有关“假根”的问题。更多还原

【Abstract】 An attempt has been made to observe the development process of sporelings of Gra-cilaria verrucosa (Hudson) Papenfuss in detail.Mature plants of tetraphyte and carpophyte were collected in 1980-1982 from the intertidal zone of Zhanshan Bay, Qingdao. The plants were brought to the laboratory, washed thoroughly with sterilized sea water, wiped and cleaned with paper towel, then excised and incubated on cover glasses in small petri dishes containing sea water at 15-20℃ under 2000 lx illum.ina.tion provided by 40W fluorescent light for 10 hours daily in the culture room. After satisfactory spore release the thalli were removed, and the released spores adhered to the cover glasses and germinated. Incubation of spores went on in sea water enriched with KN03 0.5 mM, KH2P04 0.05 mM. The medium was changed weekly.The development processes of sporelings of both tetraphyte and carpophyte that closely resemble each other are in 4 stages, primary division stage, "hemisphere body" stage, basal disc stage, and young sporeling stage.In the primary ’division stage, the spore just liberated was spherical in shape, and splitted at first into’two equivalent halves (Pls. I: 1-2, II: 1-2). Germination occurred in 15 minutes to one day after being libsrated from the mature plants.In the "hemisphere body" stage, each cell divided and formed hemisphere body continuously (Pls. I: 3-5, II: 3-5). The sporeling was seen roughly in two parts: the basal part with which the sporeling was attached to the substratum and the top part that consisted of 3-4 cells (Pis. I: 5, II: 5). This stage lasted about 2-7 days.In the basal disc stage, a distinct disc was formed at the basal part as described by Ogata (1972), and there was a distinct increase in diameter of’basal disc, i.e. from 43.8 um to 87.5um (Pis. I: 6-7, II: 6-7). This stage generally occurred after eulturing for 7-10 days.In the young sporeling stage, the center of the disc began to arch slightly, then one or more upright fronds projected gradually from there after eulturing for 30 days (Pls, I: 9-10,II:8-12).Our observation showed that there are three different ways of development for the two kinds of sporelings. About 10-20% (up to 40%) of the spores passed through the above-mentioned four development stages forming sporelings with distinct basal disc. These sporelings have strong attaching ability and are traditionally used by ordinary Gracilaria cultivation on the sea. Another 30-40% (up to 50%) of the sporelings dir- eetly developed from the "hemisphere body" without basal disc, explaining why these sporelings were often found floating in the culture medium. Although these sporelings are not suitable for the present attachment cultivation method, they might be suitable for other culture methods such as free floating method. Some 10-20% of the spore-lings showed teratological development during the second stages, with irregular cell division forming a tumour-like cell aggregate which eventually failed to survive.Some 1-5% of the sporelings showed "coalescence" in. the basal disc stage, 2-10 sporelings were seen to "coalesce" together with one single basal disc.更多还原