| Rape is a main oil crop in our country. Rice-oilseed rape rotation cultivation mode is the common cultivation mode in South China. The water remained in the field after the harvest of rice often has impact on germination as well as the growth of oilseed rape. In addition, moist and rainy winter in south China usually leads to waterlogging damage to the seedling, resulting in the decline of production. Many other cultivation measures adopted to alleviate the damage had little effect on reducing the waterlogging damage because of manpower-and resources-consuming. Therefore, the study of the mechanism how the growth regulators enhance the waterlogging resistance of B.Napus L. is essential. The success can lay foundation for planning the corresponding prevention measures against waterlogging.The seeds of Zhongyou 821 and yuhuang NO.2 coated with SA, or BR or 6-BA at different concentration were used as experimental materials to study the effects of the regulators on germination. Another experiment was performed to study the effect of the solution of the regulators on the waterlogging-resistance of the seedling under waterlogging stress. The results were as follows:1. Appropriate concentration of three regulators in the seed-coating could enhance the germination rate of B.Napus L. under waterolgging stress. The optimal regulator content in the seed-coating was 0.50mmol/L SA, 10μg/L BR or 10μg/L 6-BA, respectively. Among of them, 0.50mmol/L SA had the best effect.2. The possible mechanism that SA could improve the waterlogging-resistance of the seeds was as follows:it boosted activity of esterase and isocitrate lyase leading to the conversion of seed lipids to sugars. The conversion was favourable to germination.3. SA had no significant influence on the membrane permeability or total protein content.4. Appropriate concentration of three regulators in the seed-coating could dramatically increase chlorophyll content and net photosynthetic rate, resulting in alleviating inhibition of waterlogging on growth of the seedlings.0.50mmol/L SA, 1μg/L 6-BA had better effect.5. Appropriate concentration of three regulators all could facilitate the absorption and conversion of photosynthetic pigment and decrease PsⅡdamage and prevent light diffusion as heat. This resulted in improvement of photochemical efficiency6. The influence of three regulators on membrane peroxidation level of the seedlings varied with varieties. They had no significant influence on yuhuang NO.2. However, they all could alleviate membrane peroxidation level of the seedlings of Zhongyou 821, decreasing MDA content. The regulators had limited influence on membrane protective enzyme and only 10μg/L BR could significantly increase the activity of membrane protective enzyme.7. Appropriate concentration of three regulators could increase the content of the osmotic substances, namely soluble sugars and proteins. The soluble sugars were influenced significantly and the soluble proteins were maintained at relatively stable level.8. Appropriate concentration of three regulators could improve waterlogging-resistance of the seedlings. But the effects varied with the concentration or different regulators. Based on the comprehensive analysis,0.50mmol/L SA and 1μg/L 6-BA had better effect.9. The mechanism that three regulators could enhance waterlogging-resistance of the seedlings was similar. The regulators improved waterlogging-resistance through increasing chlorophyll content, net photosynthetic rate, absorption and conversion of photosynthetic pigment as well as the soluble sugars and decreasing membrane peroxidation level.10. Appropriate concentration of three regulators could stimulate the recovery growth the seedling cancelled the waterlogging-stress. The mechanism was similar with that of waterlogging-resistance improvement of seedlings mentioned above. Additionally, the regulators could improve root vigor and SOD activity, promoting recovery growth and recovery of membrane system. |
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