Light acquisition and use by individuals competing in a dense stand of an annual herb, Xanthium canadense |
| |
Authors: | Kouki Hikosaka Sinya Sudoh Tadaki Hirose |
| |
Institution: | (1) Biological Institute, Graduate School of Science, Tohoku University, Aoba, Sendai 980-8578, Japan e-mail: hikosaka@mail.cc.tohoku.ac.jp, Fax: +81-22-2176699, JP |
| |
Abstract: | The importance of light acquisition and utilization by individuals in intraspecific competition was evaluated by determining
growth and photosynthesis of individual plants in a dense monospecific stand of an annual, Xanthium canadense. Photosynthesis of individual plants in the stand was calculated using a canopy photosynthesis model in which leaf photosynthesis
was assumed to be function of leaf nitrogen content and light availability. The estimated photosynthetic rates of individuals
were strongly correlated with the measured growth rates. Photosynthetic rates per unit aboveground mass (RPR, relative photosynthetic
rate) increased with increasing aboveground mass, suggesting asymmetric (one-sided) competition in the stand. However, larger
individuals had similar RPRs, suggesting symmetric (two-sided) competition. These results were consistent with the observation
that size inequality over the whole stand increased with growth, but it remained stable among the larger individuals. The
RPR of an individual was calculated as the product of absorbed photon flux per unit aboveground mass (Φmass) and light use efficiency (LUE, photosynthesis per unit absorbed photon flux). Φmass indicates the efficiency of light acquisition, and was higher in larger individuals in the stand, while LUE was highest in
individuals with intermediate aboveground mass. LUE depends on leaf nitrogen content. At an early stage, leaf nitrogen contents
of smaller individuals were similar to those that maximize LUE. Light availability to smaller individuals decreased as they
grew, while their nitrogen contents did not change markedly, which decreased their LUE. We concluded that asymmetric competition
among individuals in the stand resulted mainly from lower efficiencies in both light acquisition and light use by smaller
individuals.
Received: 31 January 1998 / Accepted: 12 November 1998 |
| |
Keywords: | Intraspecific competition Light acquisition Light use efficiency Size inequality Whole-plant photosynthesis |
本文献已被 SpringerLink 等数据库收录! |
|