异型种子植物异苞滨藜的繁殖输出

Reproduction output of seed-heteromorphic Atriplex micrantha

异苞滨藜是重要的荒漠野生牧草资源,具有褐色和黑色两种异型种子;黑色种子小,种皮光滑,有光泽,包被种子的苞片较小;褐色种子大,包被种子的苞片较大。对异型种子繁殖输出的研究将为探讨其生态适应机制及生活史进化研究提供科学依据。选择准噶尔低山砾质荒漠自然种群中3个不同微生境(陡坡、缓坡和坡底),分别随机选取20株植株,测定植株高度、生物量以及种子的数量,研究种子的输出比例和繁殖分配。结果表明,1)不同微生境中植株的大小有显著差异,山坡沟底植株的个体最大,缓坡次之,陡坡最小。2)植株的总繁殖分配以及褐色种子和黑色种子的繁殖分配随个体的增大而显著增高;异苞滨藜大型植株的繁殖分配高达57.57%,褐色种子和黑色种子的繁殖分配无显著差异;中型和小型植株的繁殖分配小于30%,主要投资黑色种子。3)随植株个体的增大,异苞滨藜3个级别的植株输出的黑色种子的数量和比例均显著大于褐色种子的数量和比例;黑色种子与褐色种子比例为2.16~7.41∶1。异型种子萌发物候的不同步、繁殖输出的"灵活性"是异苞滨藜与荒漠异质环境长期适应的结果。

Atriplex micrantha,an important wild forage germplasm resource in desert regions,has seed dimorphism.It has two types of seeds that are different in shape,size,color and the size of bracts attached to fruits.Small,black seeds with a glossy,smooth testa are covered by extended bracteoles.Brown seeds are relatively larger and covered by bigger,extended bracteoles.Study of the germination phenology and reproduction output from heteromorphic seeds has significant value for understanding mechanisms of adaptation to habitat and the evolution of plant life-history strategies.In the reproduction output study,we selected 3different micro-habitats（abrupt slope,gentle slope and base of slope）in a low mountain,gravel desert population of Junggar and randomly selected 10 plants of A.micranthain each habitat to measure plant height,seed output scale and biomass allocation.The results showed：1）There were significant differences in the sizes of individual plants growing in different micro-habitats.Plants growing at the base of slope were biggest,those in the abrupt slope smallest.2）The total reproductive allocation and the reproductive allocation of brown and black seeds significantly increased with the increasing size of the individual parent plant.The reproductive allocation of big plants was 57.57%,with the reproductive investment of brown seeds equal to that of black seeds.The main reproductive investment of medium and small sized plants was to the black seeds,with their reproductive allocation less than 30%.3）With the increase of parent plant size,both the number and the ratio of black seeds outputted by the three plant height grades were significantly higher than those of brown seeds.The ratio of black seeds to brown seeds was 2.16-7.41∶1.The flexible reproductive output of heteromorphic seeds evidence how A.micranthaadapts to harsh desert environments.