Study On Development Of Gametophytes And Male-attractants From Undaria Pinnatifida

Undaria pinnatifida is one of the three main seaweed species under commercial cultivation in China. In this paper some experiments related to gametophytes development and male-attractants secreted by female gametes from Undaria pinnatifida are conducted as follows.First, the gametophytes development was studied. Female and male gametophytes development experiments were conducted under the condition of 17℃, period of light and dark 12:12 h, light intensity 40～60μmolm-2s-1. The experiments results show that when female and male gametophyes are cultivated separately female gametophytes can form mature oocysts and release eggs; while male gametophytes only form mature antheridia, but can't release sperms. When female and male gametophytes are mixed cultivate male gametophytes mature earlier than the female, but only when eggs are released are there explosive discharges of sperms. Furthermore, when female gametophytes release eggs in dark, if interfered by light, the eggs fall off from oocysts. After eggs are released for three days, if haven't been impregnated, the eggs regenerate cellular walls, grow asexually.Second, the roles of male-gametophytes in sexual reproduction were studied. The results show that eggs are able to secrete one or several kinds of volatile organic substances, which can stimulate the antheridia to release sperms and can attract sperms to swim toward the eggs to accomplish fertilization. Moreover, we studied several factors affecting secretion of male-attractants including cultivation time, temperature, light irradiance and photoperiod to optimize the conditions for secretion of male-attractants. The results show that the activation of male-attractants are the most high when the female gametophytes developed for 6 to 8 days. The optimal...