Effect of Low Night Temperature on Chlorophyll Fluorescence Parameters in Different Genotypes Tomato Leaves

In order to reveal the effects of low night temperature on chlorophyll content and PS Ⅱ activity in different genotypes tomatoes leaves.The changes of chlorophyll content and chlorophyll fluorescence parameters in chilling-tolerant wild tomato LA1777 and chilling-sensitive tomato Moneymaker under short-time 15℃(control),9℃ and 6℃ night temperature were studied.The results showed that the chlorophyll a,b content and chlorophyll a/b in two genotypes tomato leaves were significantly decreased under low night temperature stress,and the chlorophyll a and b content in Moneymaker significantly decreased than control after 1 d low night temperature treated.The Fo and NPQ increased in two tomatoes leaves under low night temperature,however,Fv/Fm,ΦPS Ⅱ,ETR and qP were decreased significantly after low night temperature treated.Only NPQ in two tomatoes had the same trend,other fluorescence parameters in Moneymaker leaves had greater changed scale than LA1777.The results showed that PS Ⅱ activity and electron transfer in cold-sensitive tomato leaves were influenced under low night temperature,and PS Ⅱ activity decreased significantly,but its decline scale was lower in cold-tolerant tomato.