种子异型植物异子蓬的生殖分配和结实格局

选择能产生异型果实和种子的一年生盐生植物异子蓬(Suaeda aralocaspica)为研究对象, 研究其生殖分配和结实格局。结果表明, 异子蓬具有较高的生殖分配和规律性的“谨慎型”结实格局。异子蓬的生殖分配高达56%。在资源充裕时, 该植物对扁圆形棕色种子(采取机会主义的萌发策略)的投资多于双凸镜形黑色种子(采取谨慎的萌发策略)的投资。异子蓬的花序类型为二歧聚伞花序, 单个果序含果实(种子)的数目为1-15个, 最多可分为4级。果序内果实的分布具有一定的规律: 第一级1个果实, 第二级2个, 第三级4个, 第四级8个。异子蓬优先将资源供给黑色种子的果实, 利用不同类型种子的发育顺序, 首先保证黑色种子的产出。具有较高的生殖分配和采取“谨慎”的生殖策略是异子蓬与其所处盐漠环境长期适应的结果。

Reproductive allocation and fruit-set pattern of seed-heteromorphic plant Suaeda aralocaspica

Aims Suaeda aralocaspica is an annual halophyte native to the inland salt desert of the Junggar Basin, Xinjiang, China. It produces two clearly defined types of fruits and seeds on the same plant. Our objective was to investigate reproductive allocation and fruit-set pattern of this species.
Methods We randomly selected 11 plants of S. aralocaspica in a population and measured the canopy diameter, shoot length, and root length and biomass allocation. We randomly selected 30 primal branches, 30 secondary branches and 30 tertiary branches, and then counted the fruit number for different node sites. We also determined the position of each fruit (seed) in the infructescence for three consecutive growing seasons.
Important findings Suaeda aralocaspica had high biomass allocation to reproductive organs and a regular fruit-set pattern that is a cautious strategy. The reproductive allocation of biomass in S. aralocaspica plants reached 56%, which is much higher than that of most annual and perennial plants. A greater proportion of biomass was allocated to oblate brown seeds (opportunistic germination strategy) than to elliptical black seeds (cautious germination strategy). The inflorescence (dichasium) may contain from one to fifteen fruits in one to four orders. The first order contains a single fruit, the second order two fruits, the third four and the fourth eight. Suaeda aralocaspica allocated resources first to black-seeded fruits. Thus, S. aralocaspica has high reproductive allocation and a cautious reproductive strategy that is adapted to the salt desert.