微齿眼子菜繁殖生物学特性的初步研究

微齿眼子菜以风媒传粉为主,具有明显的雌蕊先熟性,显示出明显的异交特性;同时其雌雄可育期部分重叠,被片、花药和柱头三者的空间布局使其极利于自花受粉,暗示了自交存在的可能性.花粉保持萌发活力的时间短(约20h)及萌发率低(＜10%)可能是导致其自然结实率(20.16%)低的主要原因.自交作为衍生性状在其有性生殖中占有相当的比例,繁育系统属于兼性的交配类型,并有向自交演化的趋势.有性生殖分配与其营养体生物量呈显著正相关,异质性程度不同的生境中,微齿眼子菜表现出不同的繁殖对策,在稳定生境中以克隆生长为主,在变动生境中有性生殖率则有所增加,存在着有性生殖与无性繁殖之间的平衡.

PRIMARY STUDIES ON THE REPRODUCTIVE CHARACTERISTICS OF POTANOGETON MAACKIANUS

Studies on the reproductive characteristics of Potamogeton maackianus A. Benn. were carried out under cultivation and in nature. P. maackianus , native to East Asia, is primarily wind pollinated and exhibits highly protogynous development: stigma receptivity prior to anther dehiscence. This is suitable for outcrossing, but stigmas are found to be still in receptive state when staminate stage begins, namely a "part overlapping" of male and female stages. The overall arrangment of stigmas, anthers and spatulate tepals is very beneficial for self pollination at the outset of anther dehiscence and suggests the possibility of autogamy. Low fruit set (20.16%) in nature may be attributed to short time of pollen viability (about 20h) and low rate of pollen germation (<10%). Experimental evidences indicate that P. maackianus is self compatible, self pollination is presumably the derived condition and there is a tendency from outcrossing to selfing. Fruit set under isolated condition (13.6%) suggests that autogamy is an important component of the breeding system. Resource allocation to sexual reproduction is propotionally correlated with the degree of total biomass. P. maackianus shows different reproductive strategies in different habitats, and exists a sexual asexual evolutionary equilibrium.