Effect of Salt Stress on the Growth and Antioxidant Enzyme Activity of Kenaf Seedlings

Kenaf is a Hibiscus member in the Malvaceae family,and exhibits fast growth,high-yield,and strong stress adaptability.The aim of the present research was to study the effect salt concentration stress on the growth and antioxidant enzyme activity of Kenaf seedlings,and further explore the physiological mechanisms of salt tolerance.Kenaf seedlings were subjected to 0 mmol/L and 140 mmol/L NaCl for 3 d,6 d and 9 d in half strength Hoagland nutrient solution and as well as 0 mmol/L,70 mmol/L,140 mmol/L,200 mmol/L NaCl concentrations for 6 d.Following treatment,weight,root length,stem length,leaf H₂O₂,and malondialdehyde(MDA) content,as well as the activity of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT) and glutathione reductase(GR),of the fresh plant samples weremeasured.The results showed that(1) Fresh weight of the treated groups were reduced by 19.63%,19.35% and 39.03%,respectively with length of treatment.Plant height decreased by 25.59%,19.17% and 18.48%,respectively.In addition,SOD activity first increased and then decreased,while POD activity showed the opposite trend.The content of MDA and H₂O₂,and CAT and GR activity had positive correlations with stress time compared to the controls.(2) With the increase in stress concentration,fresh weight of the treatment groups was reduced by 16.79%,19.35% and 44.73%,respectively.In addition,plant height decreased by 11.21%,19.17% and 23.62%,respectively.The SOD activity was higher than the control group;however,no significant differences were observed among the three.The contents of MDA and H₂O₂,and the activity of CAT and GR increased with time,but POD activity first decreased and then increased.The effects of salt stress of the kenaf seedlings increased with time and salt concentration when treating with different NaCl concentrations.The SOD and POD activities increased slightly,or even decreased,while the CAT and GR activities were relatively higher.Both CAT and GR may play an important role when responding to salt stress of kenaf seedlings.