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Determinants of the reproductive yield of competing plants in a stand

林分中竞争植物繁殖产量的决定因素

基本信息

批准号：
11440225
负责人：
HIROSE Tadaki
金额：
$ 7.94万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

We studied the effect of CO_2 elevation on the reproductive yield of Xanthium canadense. Although the plant growth and total reproductive yield (seeds plus capsules) increased with CO_2 elevation, seed production did not increase. Analysing N use in plant growth, we found retranslocation of N from leaves to seeds was retarded at high CO_2 due to increased longevity of leaves and low temperature. Translocation was lowered by lower air temperature at later growing season. Thus seed production was constrained by the availability of N.We developed a new method to separate the effect of self-shading from that of shading from neighbors and applied it to stands of Xanthium canadense established with different densities. We estimated (1) the intensity of shading for plants in the stand and (2) self-shading for plants isolated from the stand. Shading from neighbors was estimated as a subtraction of (2) from (1). We found that the interaction among individuals was strong in a stand and that the intensity increased with increasing plant densities.From an analysis of trade-off between size and number in seed production, we proposed a sink-limiting growth model, where contraints in the absorption rate of resources from mother plants were assumed with a loss of resources due to maintenance respiration. This model predicts that seed size does not increase reciprocally to the reduction in seed number. This is because an efficiency in using storage substance decreases with a smaller number of seeds and thus benefits increasing seed number at the expense of seed size. The optimal seed size is smaller than that predicted by Smith and Fretwell.

研究了CO_2浓度升高对苍耳繁殖产量的影响。虽然植株生长和总繁殖量(种子+胶囊)随着CO2浓度的升高而增加，但种子产量并没有增加。通过分析氮素在植物生长中的作用，我们发现，在高CO_2条件下，由于叶片寿命的延长和低温的影响，氮素从叶片到种子的再运转受到了抑制。生长后期气温较低，降低了转运量。因此，种子生产受到氮素有效性的制约。我们开发了一种新的方法来区分自遮荫和邻遮荫的效果，并将其应用于不同密度的加拿大苍耳林。我们估计了(1)林分植物的遮荫强度和(2)林分隔离植物的自我遮荫强度。邻居的阴影被估计为从(1)中减去(2)。通过对种子生产中个体大小和数量的权衡分析，提出了一个库限生长模型，该模型假定母植物对资源的吸收速率受到限制，而维持呼吸造成资源的损失。该模型预测种子大小并不与种子数量的减少成反比。这是因为使用贮藏物质的效率随着种子数量的减少而降低，因此有利于以种子大小为代价增加种子数量。最佳种子尺寸小于Smith和Fretwell的预测。