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| The effect of exogenous CaCl2 on photosynthesis, antioxidant system, and chloroplast ultrastructure of tomato leaves under low night temperature (LNT) was investigated. Tomato seedlings were pretreated with 27 mM CaCl2, 5 mM EGTA respectively for 4 days and then exposed to LNT treatment at 6 C for 7 d. Plants treated with CaCl2 showed higher photosynthesis, increased stomatal aperture and chloroplast area, and decreased number of starch grains under LNT stress than those treated with distilled water. LNT increased the contents of superoxide radicals, hydrogen peroxide, and malondialdehyde, whereas calcium application reduced the contents of these compounds. The increase in antioxidant activities caused by LNT stress was also enhanced by the application of exogenous calcium. The opposite effects were observed with ethyleneglycol-bis-(2-aminoethyl) tetraacetic acid pretreatment. CaCl2 application improved photosynthesis in LNT-stressed plants. Such improvement was associated with increased stomatal conductance, improved antioxidant activities, and adjusted chloroplast structure. These results suggest that CaCl2 application improved photosynthesis in LNT-stressed plants. Such improvement was associated with increased stomatal conductance, improved antioxidant activities, and adjusted chloroplast structure. It provided fundamental information for further molecular mechanism research. |
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| Keywords:calcium; photosynthesis; chloroplast ultrastructure; antioxidant system; low night temperature;tomato |
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