The characteristic of dry matter and nutrient accumulation and transportation in leaves in winter oilseedrape (Brassica napus L.)

Leaf is the main photosynthetic organ for plants, but for rapeseed, it gradually drops out after the bud period. To increase nutrient use efficiency, it is important to evaluate the nutrient accumulation and distribution in green leaves and defoliation. Two cultivars of rapeseed (Brassica napus L., HS No.5 and ZYZ No.12) were selected to study the accumulation and transportation of dry matter and nutrients in leaves of rapeseed. The results show that the accumulation amounts of dry matter in green leaves of the two cultivars reach their maximum values at the late seedling period and are decreased quickly after the blooming period, while the dry matter accumulation of defoliation is increased quickly after the bud period. The dry matter accumulation amounts of total leaves are increased at first and then decreased, and reach their maxima at the blooming period. The dry matter accumulation of total leaves and defoliation of ZYZ No.12 are more than those of HS No.5, and the differences are significant along with the growth of rapeseed. The N content of green leaves is decreased at the seedling period and then increased because of the application of wintering fertilizer, and decreased again after the bud period. The N content of defoliation is decreased gradually at the seedling period and keeps steady after the bud period. The P content of green leaves is increased slowly at the seedling period and decreased quickly after the bud period. The P content of defoliation is decreased at the seedling period and reaches the minimum at the bud period, but at the mature period it is increased a little. The K content of green leaves decreased quickly at 50 d after seeding, reaches the minimum at 70 d, and then keeps steady. The K content of defoliation reaches the minimum at the bud period and then fluctuates greatly. The changes of nutrient concentrations are similar for the two varieties, and the contents of nutrients of HS No.5 are slightly lower than those of ZYZ No.12 both in green leaves and defoliation. The accumulation amounts of N, P2O5 and K2O reach their maxima at the bud period, seedling period and blooming period respectively in both green leaves and total leaves and then were decreased after those period. Nutrient accumulations of defoliation are increased after the bud period and reach their maxima at harvest. The transportation ratios of dry matter,N, P2O5 and K2O in rapeseed leaves are 25.5%, 82.9%, 75.4% and 45.8% in HS