Regulatory Mechanisms of Reproductive Effort in Plants II. Plasticity in Reproductive Energy Allocation and Propagule Output of Glycine max Merr. (Leguminosae) Cultivated at Varying Densities and Nitrogen Levels
Article first published online: 3 FEB 2005
Plant Species Biology
Volume 1, Issue 2, pages 181–194, December 1986
How to Cite
Nagai, Y. and Kawano, S. (1986), Regulatory Mechanisms of Reproductive Effort in Plants II. Plasticity in Reproductive Energy Allocation and Propagule Output of Glycine max Merr. (Leguminosae) Cultivated at Varying Densities and Nitrogen Levels. Plant Species Biology, 1: 181–194. doi: 10.1111/j.1442-1984.1986.tb00026.x
- Issue published online: 3 FEB 2005
- Article first published online: 3 FEB 2005
- Received February 5, 1987. Accepted May 30, 1987.
- Glycine max;
- reproductive allocation;
- reproductive effort;
- trade-off in reproductive traits
Abstract Plasticity in growth, reproductive energy allocation (RA), and reproductive output were studied in Glycine max Merr. Cv. Enrei (Leguminosae) grown under varying densities and soil nitrogen levels.
Marked plastic responses were detected in individual biomass, the patterns of resource allocation to total reproductive structures (RA) and also to propagules, reproductive outputs, and propagule weight under changing densities and soil nitrogen levels. Plants cultivated at higher densities exhibited proportionately lower individual biomass, lower RA, lower seed output, and smaller seed size in response to increasing density and decreasing soil nitrogen levels, although some deviations were observed, especially in the highest density plot with no fertilization. Differences due to different N-levels were not as great as those to changing density, which may in part be due to the fact that soybean has nitrogen-fixing bacteria in root tubercles, just as in any other Leguminosae. Fecundity was also maintained at the similar high rates of 80–97% in all plots examined, although slight but steady decreases were noted with increasing density. This resemblance in fecundity may be due to its strong inbreeding system.
Another important finding was that seed production under limited resource availability, notably lack of ample solar radiation due to strong interference at higher density plots, is exceedingly costly. This was most clearly exhibited by a sharp increase in relative energy partitioning to a single propagule in response to the increased density, the relative energy cost to a single propagule (RA) increasing from one to seven-fold. The results obtained in this study coincide well with the findings made in other plants, e.g., Helianthus annuus, Oryza sativa, and Coix ma-yuen, with the same experimental designs.