Phosphorus stress effects on growth and seed yield responses of nonnodulated soybean to elevated carbon dioxide.
Cure J.D. | Rufty T.W. Jr. | Israel D.W.
The influence of P availability on plant responses to elevated atmospheric CO2 concentrations has received limited research attention. Therefore, an experiment was conducted to examine the effect of a wide range of P availabilities on plant response to enriched atmospheric CO2. Nonnodulating soybean [Glycine Max (L.) Merr., 'Lee'] plants were grown from germination to maturity in controlled environment chambers at 350 or 700 microliter L-1 CO2 and supplied with a complete nutrient solution containing either 0.005, 0.10, 0.25, 0.50, or 1.00 mM P. Growth and seed yield were maximized at the 0.25 and 0.50 mM P concentrations at 350 and 700 microliter L-1 CO2 respectively. Growth and yield were significantly increased by CO2 enrichment at all except the lowest P concentration. The stimulation of growth at high CO2 was consistently associated with increased leaf area, net assimiluation rate, P uptake, and P utilization efficiency in the production of dry matter. When averaged over the four highest P levels, total root mass was increased 63% by CO2 enrichment, but P uptake efficiency per unit root mass was decreased 22%. The yield enhancement of 23 to 57% at high CO2 was associated with increases in the number and size of seed. Carbon dioxide enrichment had no significant effect on harvest index. The results indicate that CO2 enrichment can result in stimulation of growth and yield of nonnodulated, NO3(-1)-fed soybean plants, even at concentrations of P that limit plant growth at ambient CO2 concentrations.
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