Variable rsponses of mesophyll conductance to substomatal carbon dioxide concentration in common bean and soybean

Authors: Bunce, James

Submitted to: Photosynthetica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2010
Publication Date: 12/15/2010
Citation: Bunce, J.A. 2010. Variable rsponses of mesophyll conductance to substomatal carbon dioxide concentration in common bean and soybean. Photosynthetica. 48:507-512.

Interpretive Summary: The movement of carbon dioxide within leaves has recently been recognized to be an important limitation to photosynthesis, hence to plant growth rates. Whether the concentration of carbon dioxide affects this limitation is controversial. This work used a new method of estimating this limitation, and found that the limitation was sensitive to carbon dioxide concentration in bean, but not in soybean. This work will be of use to scientists attempting to increase crop growth rates by increasing photosynthesis, and to scientists predicting the responses of crops to increasing atmospheric carbon dioxide concentrations.

Technical Abstract: Some reports indicate that mesophyll conductance to carbon dioxide varies greatly with the sub-stomatal carbon dioxide concentration during the measurement, while other reports indicate little or no change. I used the oxygen sensitivity of photosynthesis to determine the response of mesophyll conductance to sub-stomatal carbon dioxide concentration over the range of about 100 to 300 ppm sub-stomatal carbon dioxide concentration at constant temperature in common bean and soybean grown over a range of temperatures and light levels. In soybean grown and measured at high light there was only a slight decrease in mesophyll conductance with sub-stomatal carbon dioxide concentration. With lower light during the measurement of mesophyll conductance, and especially with low light during plant growth, there was a substantial decrease in mesophyll conductance with sub-stomatal carbon dioxide concentration. In common bean, the same range in sub-stomatal carbon dioxide concentrations resulted in much larger decreases in mesophyll conductance than in soybean. Growth temperatures of 20 to 30 C had little influence on the response of mesophyll conductance to sub-stomatal carbon dioxide concentration or its absolute value in either species. It is concluded that these two species differed substantially in the sensitivity of mesophyll conductance to sub-stomatal carbon dioxide concentration, and that light but not temperature during leaf development strongly affected the response of mesophyll conductance to sub-stomatal carbon dioxide concentration.