Effects of Spermidine+Gibberellin on Seed Germination and Seedling Physiological Indexes of Citri grandis Tomentosa at Low Temperatures
The effects of spermidine(Spd)+gibberellin(GA3)on seed germination,seedling root growth,root activity,and physiological indexes of Citri grandis Tomentosa were studied at low temperatures to cultivate sturdy seedlings.The concen-trations of spermidine were set to 0(CK),0.10,0.15,0.20,and 0.25 mmol·L-1,respectively,and 80 mg·L-1 GA3 solution was added for soaking and culture.The germination rate,germination potential,seedling root length,seedling length,root weight,root length/seedling length,root weight/seedling weight,antioxidant enzyme activity,osmotic adjustment substance,and membrane peroxide content were measured.The results showed spermidine+gibberellic acid had a synergistic effect on the germination of C.grandis Tomentosa seeds,and the germination rate,germination potential,and germination index signifi-cantly improved at the condition of low temperature.When gibberellic acid was used alone,the growth of seedling roots was inhibited,and the addition of spermidine significantly alleviated this effect.The degree of alleviation was positively correlated with the concentration of Spd.The root length,root weight,root length/seedling length,root weight/seedling weight,and root activity were greatest in the treatment with 0.20 mmol·L-1 spermidine+80 mg·L-1 gibberellic acid.The activities of antioxi-dant enzymes(SOD,POD,and CAT)in the roots of the plants significantly increased.The contents of the osmotic adjustment substances proline and soluble protein increased,and the content of malondialdehyde(MDA)decreased.The combination of spermidine and gibberellic acid promoted the seed germination,root growth,and root activity of C.grandis Tomentosa;alle-viated the damage caused by low temperature to the roots of C.grandis Tomentosa seedlings;and improved the cold resistance of the seedlings.