CO2Compensation Concentration, Rate of Photosynthesis, and Carbonic Anhydrase Activity of Plants

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Abstract
Leaves of a number of plant species were surveyed for their CO2 compensation concentration which is one of the distinguishing characteristics used to classify plants on the basis of their photosynthetic capacity. Monocot genera with low CO2 compensation values are mainly limited to tribes of Chlorideae, Paniceae, Andropogoneae, Tripsaceae, and a part of Festuceae in Gramineae. Major grain crops, except corn (Zea mays L.) and sorghum (Sorghum vulgare Pers.), are primarily in the tribes of Hordeae, Aveneae, and Oryzeae, and have high CO2 compensation concentrations. Seven genera of dicots with low CO2 compensation occur in the four families of Amaranthaceae, Chenopodiaceae, Portulacaceae, and Euphorbiaceae. Major dicot crops are in the families Leguminosae and Malvaceae and have high CO2 compensation points. Low CO2 compensation concentration also is correlated with low carbonic anhydrase activity. Conversely, high CO2 compensation concentration plants have a high carbonic anhydrase activity. Data on the influence of light intensity and temperature on the rate of photosynthetic CO2 fixation in leaves from plants with high and low CO2 compensation concentration indicate differential responses of photosynthesis to these environmental factors. The data are interpreted as supporting a hypothesis for competition by specific plants.