| Winter oilseed rape at late seeding, was easily affected by low temperature. It could bring seed vigour decline and make seedling infirm, as a result it effects plant growth and development. The trials studied the effects of exterior 6-BA on oilseed rape (B. napus var Qinyou No. 9)seed germination, seedling growth, chilling resistance and oilseed rape seeding directly in farm. The mechanism of oilseed rape seed treated with 6-BA was also studied and it could offer theoretical basis for the application of 6-BA to oilseed rape seeding directly. The main results were as follows:1. The effects of seed soaking with 6-BA solution (1,5,25,125mg L-1) on seed germination and seedling growth of oilseed rape were different. Results showed that 1,5mg L-16-BA enhanced the seed germination rate and 5mg L-1 6-BA increased the coefficient of germination. All concentrations of 6-BA solutions enhanced the vigour index of oilseed rape seed. The activity of total ehydrogenase, lipase and a-amylase activity of gemninating seed were increased significantly. When concentrations of 6-BA solution increased, the souble sugar content was raised and the amino acid content was decreased. 1, 5mg L-1 6-BA reduced electrolyte leakage and 5mg L-1 6-BA decreased the content of MDA while 1, 5, 25 mg L-1 6-BA increased flee proline content. 6-BA had a distinct stimulation on seedling growth, increasing chlorophyl content and root vigor. Accordingly, 1 to 5 mg L-1 is the suitable concentration of 6-BA.2. The study was to investigate the effects of seed soaking with different levels of 6-BA (1, 5, 25, 125 mg L-1) on seedling growth and physiological characteristics of oilseed rape. Results showed that under low temperature (4℃) length and area of leaf, plant height and root length of oilseed rape seedling were increased treated with 6-BA. It had an obvious restraining effect on the width of leaf, the plant dry weight accumulation, however, root to shoot was promoted and the activity of nitrate reductase (NR) in leaves was improved. Under low temperature, exterior 6-BA reduced electrolyte leakage and the MDA content of seedling in leaves, while increased the cytoplasmic osmosis and content of antioxidant, improving the activities of protective enzymes (SOD, POD, CAT) significantly and lowering the overdioxygenation of membrane lipid. After dipping seeds with 6-BA, it remarkably improved the growth and chilling resistance of rape seedling under low temperature, and 5rag L-1 is the suitable level.3. This study was to evaluate the action mechanisms of 6-BA applyed exteriorly on the growth and chilling resistance of oilseed rape seedlings before or under a low temperature (4℃) stress and resuming growth. Results showed that under low temperature, the oil rapeseed seedling was damaged at a certain extent. 5 mg L-1 of 6-BA accelerated the growth of seedlings, controled the chemical matter in cell and protected the stabilization of cell membrane, so 6-BA improved the chilling resistance of seedlings. After resuming growth the electrolyte leakage and the content of MDA decreased and the content of proline and soluble protein content increased. The soluble sugar decreased and the changes of carotenoid and content of ASA were small. The activities of three protective enzymes were obviously increased and the damage in low temperature was lessened.4. This study was to evaluate the effects of sowing date and seed soaking with 6-BA on the growth and economic characters of oilseed rape (Brassica napus L.). Results showed that different phototemperature condition of oilseed rape seed growing due to different sowing date resulted in a great difference in growth and economic characters. On the first (October 20th) and second seeding date (October 27th), 6-BA increased the number of leaf and leaf dry weight before winter. On the third seeding date (November 4th) the growth was restrained, decreasing the number of leaves and leaf dry weight. On the second seeding date (October 27th) 6-BA shortened the length of oilseed rape main inflorescence, enhanced the pod density of main inflorescence, number of main inflorescence and increased the number of branch, number of total pods and pod dry weight, making a good baisis for oilseed rape yield.
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