Effects of seed and seedling vigor on antioxidative isozyme activity and cold acclimation capability of winter oilseed rape

摘要

Overwintering capacity is a major factor influencing growth and yield of winter oilseed rape (Brassica napus L.) in temperate regions. Antioxidant enzymes can protect plant cells from oxidative damage imposed by freezing stress. Therefore, this research was conducted to evaluate the relationship between frost resistance and antioxidant capacity of winter oilseed rape. High and low vigor seedlings of winter rapeseed were cold-hardened at low non-freezing temperature for 0, 14, 28 and 42 days. Freezing tolerance capability of seedlings was determined by the estimation of LT50. Changes in the isozymes activities of antioxidant enzymes (catalase, peroxidase and superoxide dismutase) in the leaves of seedlings from different vigor seed lots during cold acclimation were identified by densitometry of isozyme bands on polyacrylamide slab gels. The LT50 of the seedlings from all seed lots was decreased with increasing acclimation duration up to 28 days. Both acclimated and non-acclimated seedlings from the lowest vigor seed lot (SV3) had the least frost resistance. The greatest activity of CAT(1) and POX1 occurred when winter oilseed rape plants were acclimated for 14 days. Other isozymes including CAT(2), POX2, SOD1 and SOD2 did not show significant responses to cold acclimation period. CAT(1) and SOD1 activities were decreased with decreasing seedling vigor, while two POX isozymes did not show significant response to seedling vigor. Therefore, sowing high vigor seeds can produce vigorous seedlings which improve acclimation capability and freezing tolerance of winter oilseed rape via enhancing the activities of CAT(1) and SOD1 isozymes.