Abstract
The effects of exogenous melatonin on the growth, chlorophyll fluorescence parameters and related components of distribution of heat dissipation in tomato seedlings under Ca (NO3) 2 stress were studied in this experiment. The results showed that calcium nitrate stress inhibited the growth of tomato seedlings, reduced Y (II), Fv’/Fm’, qP and ETR, and produced photoinhibition on tomato seedlings. Spraying exogenous melatonin could increase the growth of tomato seedlings under calcium nitrate stress. Melatonin regulated qP and ETR under calcium nitrate stress, reduced the ratio of Y(NPQ), Y(NO), and increased the ratio of Y(II). Further analysis of NPQ and its three components, which including qE, qT and qI, showed that NPQ and its three components were significantly increased in the stress treatment group, while melatonin could inhibit the increase. Thus, it indicated that exogenous melatonin could effectively alleviate the growth of tomato seedlings under calcium nitrate stress, maintain the reasonable distribution of light energy, and protect the photosystem II from light damage caused by excess light energy.
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