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Elevated root-zone CO protects lettuce plants from midday depression of photosynthesis



Elevated root-zone CO protects lettuce plants from midday depression of photosynthesis



Environmental and experimental botany 61(1): 94-101



Effects of elevated root-zone (RZ) CO on photosynthesis and productivity of lettuce plants grown in a greenhouse were investigated over a period of 2 weeks. Four levels of RZ CO were imposed on lettuce roots 3 weeks after transplanting by supplying air with CO concentrations in the range between ambient (360 ppm) and 50,000 ppm. Elevated RZ CO produced no significant increase of photosynthetic CO assimilation (A) and stomatal conductance (g(s)) during the first 2-3 h following sun rise. Compared to control plants grown at ambient RZ CO, elevated RZ CO treatment resulted in significant increases and decreases in A and g(s), respectively, during the late morning. By midday, however, there was a substantial decline in A, which could attribute to both increase in stomatal limitation of A and dynamic photoinhibition of PSII as g(s) and Fv/F(m) ratios were lowest in all plants during midday between 13:00 and 14:00 h. Midday depressions of A and Fv/F(m) ratios were alleviated in elevated RZ CO treated plants. However, elevated RZ CO significantly decreased g(s) accompanying higher midday RWC. During the onset of different RZ CO treatments, leaf expansions were measured to examine the response of leaf growth to elevated RZ CO over a period of 5 days. Productivities of shoot and root were also determined by the end of 2 weeks treated with different RZ CO. The results indicate that elevated RZ CO enhanced leaf area, shoot and root productivities. It was predicted that increasing RZ CO could alleviate midday depression of photosynthesis and hence increase the productivity of lettuce plants.

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Accession: 015691550

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DOI: 10.1016/j.envexpbot.2007.04.001



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