[Antioxidant enzyme activities and proline content in maize seedling and their relationships to cold endurance]

This paper studied the catalase (CAT) and peroxidase (POD) activities and proline (Pro) content in the seedling's root, mesocotyl (including coleoptile node) , and coleoptile (including infancy leaf) of two maize inbred lines Huang C (cold-endurance) and Mo17 (cold-sensitive), and their relationships to cold endurance under low temperature stress (5 degrees C, 3 d). The results showed that under the low temperature stress, Huang C had a significantly higher relative growth rate of mesocotyl and coleoptile than Mo17, and the change rates of CAT and POD activities and Pro content in the root, mesocotyl and coleoptile of Huang C were higher than those of Mo17. The plasma membrane permeability of the three segments of both inbred lines was significantly increased, but Huang C had significantly lower plasma membrane permeability than Mo17. Compared with those under normal temperature, the seedlings under low temperature stress had higher CAT activity and Pro content, and the increment was higher in Huang C than in Mo17. The POD activity in the three segments of the seedlings under low temperature stress was reduced, and the decrement was lower in Huang C than in Mo17. Stepwise regression analysis showed that under low temperature stress, the dry matter accumulation in cold-endurance line Huang C was mainly related to Pro content, while that in cold-sensitive line Mo17 was mainly related to POD activity. Mesocotyl was the most responsive tissue to low temperature. The change rate of Pro content in mesocotyl was more closely correlated with the cold endurance of maize inbred lines than the other physiological parameters.