Inducing Effects and Its Biological Mechanisms of ABA on the Chilling Resistance of Sweet Pepper Seedlings

To study the inducing effects and biological mechanisms of abscisic acid(ABA) on the chilling resistance of plant,sandy culture method was conducted to examine the effects of ABA on the lipid peroxidation,electrolyte leakage,osmosis-regulating substances,reactive oxygen species,antioxidant enzyme activities and endogenous hormones balance in sweet pepper(Capsicum annuum) seedlings under cold stress.Sweet pepper seedlings were irrigated with 10 mL/plant of 0.10,1.0 or 10 mg/L ABA.The seedlings were grouped and grew under normal temperature(25℃～30℃) for 7 d or domesticated under low temperature(10℃～15℃) for 30 d,and then under cold stress(5℃) for 48 h.Under low temperature,ABA promoted the lateral root growth in the domesticated seedlings and reduced respiration rate,electrolyte leakage and MDA of both the seedlings in domesticated and normal temperature,especially in the domesticated seedlings.The concentration of proline,soluble sugar,potassium in leaf and ABA in stem apex were increased in both the seedlings in domesticated and normal temperature,observably in the proline contents.The superoxide dismutase(SOD) activity and H2O2 contents was increased significantly in the seedlings under normal temperature but decreased in domesticated seedlings;Catalase(CAT) and POD activity were decreased in the seedlings under normal temperature and no change in domesticated seedlings.Contents of IAA,ABA,and value of ABA/ZR were increase observably in both seedlings.As a result,ABA alleviates chilling resistance in sweet pepper seedlings through decreasing respiration rate,and increasing content of proline,soluble sugar,K+,especially in the domesticated seedlings.