Photosynthesis and Stomatal Conductance with CO2-Enrichment of Containerand Field-Grown Soybeans
1984
Sionit, N. | Rogers, H. H. | Bingham, G. E. | Strain, B. R.
The present experiment was an attempt to study the differences between photosynthetic responses of pot-grown and field-grown soybean [Glycine max (L.) Merr., ‘Bragg’] plants to atmospheric CO₂ enrichment at six levels of irradiance and four leaf temperatures. Plants were grown in field soil or in pots containing an artificial substrate at five elevated atmospheric CO₂ levels and two water regimes in open top field chambers. Under well-watered conditions plants grown in the pots had lower stomatal conductances and lower rates of net photosynthesis than plants grown in the field. However, the field-grown plants responded to a less extent to increasing atmospheric CO₂ concentration than pot-grown plants. The photosynthesis- irrdiance relationships were linear in the field-grown plants and curvilinear in the pot-grown plants. At the highest irradiance level tested (1400 µmol m⁻² s⁻¹), the field-grown plants had maximum net photosynthetic rates of 43 and 48 mg CO₂ dm⁻² h⁻¹ at 332 and 623 µL L⁻¹ CO₂ respectively. The pot-grown plants were irradiance saturated at a level of 700 µmol m⁻² s⁻¹ and net leaf photosynthetic rates were 18 and 28 mg CO₂ dm⁻² h⁻¹ at 332 and 623 µL L⁻¹ CO₂, respectively. Water stress caused a reduction in both stomatal conductance and net photosynthetic rate in the leaves of pot-grown plants. The effect of leaf temperature on net photosynthethis and stomatal conductance depended upon the atmospheric CO₂ concentration and rooting media. High temperature increased net photosynthetic response to CO₂ enrichment at high CO₂ concentrations but not at low CO₂ concentrations.
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