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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浓度升高对加拿大苍耳（Xanthium canadense）繁殖产量的影响。随着CO_2的升高，植株的生长和总繁殖产量（种子加蒴果）增加，但种子产量没有增加。通过对植物生长过程中氮素利用的分析，我们发现在高co2条件下，由于叶片寿命延长和低温，氮素从叶片向种子的再转运受到阻碍。生长期较低的气温降低了易位。本文提出了一种分离自遮荫效应和邻遮荫效应的新方法，并将其应用于不同密度的加拿大苍耳林。我们估计了(1)林内植物的遮阳强度和(2)离林植物的自遮阳强度。从(1)中减去(2)估计来自邻居的阴影。结果表明，林分个体间相互作用较强，且相互作用强度随密度的增加而增加。通过对种子生产中大小和数量之间权衡的分析，我们提出了一个库限制生长模型，其中假设来自母植物的资源吸收率受到限制，并且由于维持呼吸而造成资源损失。该模型预测种子大小不随种子数量的减少而增加。这是因为储存物质的使用效率随着种子数量的减少而降低，从而有利于以种子大小为代价增加种子数量。最佳种子大小比Smith和Fretwell预测的要小。