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.

我们研究了CO_2升高对Xanthium Canadense生殖产量的影响。尽管随着CO_2升高的增加，植物生长和总生殖产量（种子和胶囊）增加，但种子的产量并未增加。分析氮在植物生长中的使用时，我们发现，由于叶子的寿命增加和低温，在高CO_2上将N从叶到种子的转递。在后来的生长季节，空气温度降低了易位。因此，种子的产生受N的可用性的限制。我们开发了一种新方法，将自我阴影与邻居的阴影效应分开，并将其应用于具有不同密度的Xanthium Canadense架子。我们估计了（1）植物中植物的阴影强度以及（2）与架子分离的植物的自我阴影。邻居的阴影估计为（1）的（2）的减法。我们发现，个体之间的相互作用在一个林分中很强，并且强度随着植物密度的增加而增加。从种子生产中的大小和数量之间的权衡分析，我们提出了一种限制性的生长模型，在这些模型中，由于维持退休而导致了资源损失，因此，假定，在母植物的吸收率中，对母植物的吸收率存在相反。该模型预测，种子大小不会相互增加，因为种子数量的减少。这是因为使用储存物质的效率随少量种子而降低，因此以种子大小为代价增加种子数量。最佳种子大小小于Smith和Fretwell所预测的种子大小。