Studying the effect of cold stress on green basil, violet basil, tomato and lettuce using chlorophyll fluorescence technique

Cold stress causes great yield reduction in greenhouse crops. In order to study the damage of cold stress in some greenhouse crops, a factorial experiment based on CRD was conducted with two factors including temperature in two levels (4 and 21 ºC) and plant species in four levels (green basil, violet basil, tomato and lettuce) with 3 replications. To apply the cold stress, these plants were placed under 4°C and dark condition for 12 hrs. The results showed that minimal chlorophyll fluorescence of basil plants was significantly higher in control plants compared to the cold-stressed ones, whereas in lettuce it was significantly higher in cold-stressed plants. In this experiment, it was also observed that maximal fluorescence (Fm), variable fluorescence (Fv) and maximum quantum efficiency of photosystem II (Fv/Fm) of green basil, violet basil and tomato plants were significantly lower under cold stress compared to the control. In contrast, these parameters were increased by cold stress in lettuce. These findings confirm the resistance of lettuce to cold stress and stimulating this plant to increase the maximum quantum efficiency of photosystem II under low temperature conditions.