Effects of Exogenous Abscisic Acid on Growth and several Physiological Characteristics of Broccoli under Cold Stress

The growth situation and activity variation of SOD and POD of different broccoli cultivars under cold stress were evaluated. After that, the relaxation effect of exogenous ABA on plant growth was studied by using broccoli cultivar ‘Cuilv’ (CL) as test material. The results showed that: (1) Exposure of broccolis to cold stress resulted in inhibition on plant height and stem diameter. Meanwhile, the activities of SOD and POD and soluble sugar content of the broccolis decreased significantly. However, different cultivars showed different responses to cold stress. The cultivar CL and MTL were greatly suppressed by cold stress, while cultivar YX and AU showed less influence. (2) ABA at 100 mg·L-1 improved plant height and stem diameter of CL significantly. The SOD and POD activities of plants treated by 50, 100 and 150 mg·L-1 of ABA were significantly higher than that of control. In addition, 100 mg·L-1 ABA increased mostly the activities of SOD and POD among all treatments. (3) Exogenous ABA significantly enhanced the soluble sugar content of CL. After 15 days of cold treatment followed by 15 days of recovery treatment, the soluble sugar contents of CL plants treated by 50, 100 and 150 mg·L-1 ABA were significantly higher than that of control and maintained at a high level.