| Abstrakt: |
Limitations in nutrient availability apparently can restrict plant response to CO2enrichment; however, the alterations in physiological processes associated with such restrictions have not been defined. This experiment was conducted to investigate certain physiological responses of N‐limited soybean [Glycine max(L.) Merr. cv. Lee] plants growing in a CO2enriched environment and to examine their role in determining growth and yield. The nonnodulating soybean plants were grown to maturity in controlled environment chambers at 350 or 700 μL L−1CO2and at 0.05, 1.0, 2.5, 5.0, or 10.0 mMKNO−3supplied in nutrient solution. Substantial increases in whole‐plant growth and seed yield occurred in both CO2treatments with increasing nitrate levels; the increases were greater, however, at high CO2. At all NO−3levels except the lowest, exposure to high CO2resulted in increased total leaf area, mean net assimilation rate, NO−3uptake, and N utilization efficiency. Increased NO−3uptake was associated with larger root systems, as uptake per unit of root mass was lower than controls. Carbon dioxide enrichment had little effect on dry matter partitioning among plant parts or harvest index. Alterations in partitioning were related to differences in NO−3supply. The results suggest that atmospheric CO2enrichment can stimulate seed yield of soybean even when the availability of N in the rhizosphere is limited. |
Plný text