2000 Fiscal Year Final Research Report Summary
Determinants of the reproductive yield of competing plants in a stand
| Project/Area Number |
11440225
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B).
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
生態
|
|---|
| Research Institution | Tohoku University |
|---|
Principal Investigator |
HIROSE Tadaki Tohoku University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (90092311)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
HARADA Yuko Tohoku University, Graduate School of Science, Assistant Prof, 大学院・理学研究科, 助手 (80312544)
HIKOSAKA Kouki Tohoku University, Graduate School of Science, Associate Prof, 大学院・理学研究科, 助教授 (10272006)
SAKAI Satoki Tohoku University, Graduate School of Science, Associate Prof, 大学院・理学研究科, 助教授 (90272004)
HIKOSAKA Hisae Tohoku University, Graduate School of Science, Assistant Prof, 大学院・理学系研究科・附属植物園, 助手 (20323503)
|
|---|
| Project Period (FY) |
1999 – 2000
|
| Keywords | plant stand / competition / reproduction / interaction / nitrogen use / light acquisition / seed production |
|---|
| Research Abstract |
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.
|
