Effect of exogenous melatonin on photosynthetic characteristics in cucumber seedlings under cadmium stress: a rapid detection method for the cadmium resistance

College of Horticulture, Sichuan Agricultural University, Chengdu, 611130, China

^* Corresponding author’s e-mail: 414657644@qq.com

Abstract

Water and soil pollution by cadmium have caused severe impact to environment, especially the inhibition of plant growth due to the cadmium stress. Taking cucumber seedlings as the materials, the effect of exogenous melatonin on cadmium uptake and photosynthetic capacity of cucumber seedlings under cadmium stress were studied. The results showed that the leaf area and chlorophyll content of cucumber seedling leaves were decreased after cadmium stress, while the decrease in leaf area was alleviated after the addition of exogenous melatonin. And there was less cadmium content in the roots of cucumber seedlings than that of cadmium stress treatment alone. Exogenous melatonin increased net photosynthetic rate (Pn) with the enhancement of stomatal conductance (Gs), transpiration rate (Tr) of cucumber seedlings. Further analysis of the chlorophyll fluorescence parameters revealed that the decrease of the effective quantum yield of photochemical energy conversion in PSII (Y(II)), and the photochemical fluorescence quenching coefficient (qP) by cadmium stress treatment were mitigated by addition of melatonin. The results indicated that exogenous melatonin could significantly alleviate the damage of cadmium stress on photosynthetic organs of cucumber seedlings, improve their photosynthetic capacity and reduce the damage caused by cadmium stress. It could be recommended to apply melatonin cultivation of cucumber under cadmium stress.