| Rape is a main oil crop in our country. Rice - oilseed rape rotation cultivation mode is one of the main cultivation mode in South China. The water remained in the field after the rice harvest often has influence on germination and growth of oilseed rape. In addition, moist and rainy winter in south China usually results in the moisture and waterlogging damage to the seedling and the decline of production. Many other cultivation measures adopted to alleviate the damage failed because they are manpower- and resources-consuming and had little effect. The present study is expected to exploit another pathway to alleviate the damage of moisture and waterlogging to oilseed rape. Three kinds of plant growth regulators, namely brassinolide (BR) and salicylic acid (SA) and 6-benzyl aminopurine (6-BA), were used as regulators to study the effect of them to improve the growth and alleviate the damage from moisture or waterlogging.Zhongyou 821 and yuhuang NO.1 coated with SA, BR 6-BA at different concentration were used as experimental materials to study the effects of three regulators on the germination ratio under waterlogging condition and the growth of the root and stem after the water draining. Besides this, another experiment was completed in this study. The rape seedlings under waterlogging stress were sprayed with the mentioned plant growth regulators with different concentration. The effects of plant growth regulators on the physiological indexes of the seedlings and the recovery growth after the water draining were studied. The results are as follows:1 .The rape seeds were coated with the regulators with different concentration and germinated under waterlogging condition. In the experimental, the lower concentration of coating has no significant effect on germination ratio. The ratio of the seed coated with middle concentration was higher than that of the control. Higher concentration of 6-BA (10mg/L) obviously inhibit the germination. So does higher concentration of BR (1mg/L) .2. Further studies indicated that all the treatments had the similar effects on the growth of the root or the stem of the two lines. On one hand, most treatments could significantly improve the growth of the root except 10mg/L6-BA which significantly inhibited the root growth. Among the treatment, 100μmol/L SA have the best effect. On the other hand, all the treatments could significantly promote the growth of the stem, especially 0.1mg/L BR which had the best effect. The results suggested most treatments could improve the recovery growth of the root and stem, and 0.1mg/L BR was regarded as the most perfect treatment. 3.The seedlings were sprayed with the regulators at 5-leaves stage followed by waterlogging stress and then related physiological indexes were tested. Most of the treatment reduced the membrane permeability of the leaves. The content of water, chlorophyll,three osmotic substances (soluble sugar, soluble protein, free proline) of the leaves and the root activity were increased resulting the increasing of waterlogging resistance. The treatment with 0.1-1 mg/L 6-BA has the best effect among the all. All the treatments had no significant influences on the activity of three membrane protective enzymes (SOD, POD, CAT) or the content of MDA in the leaves of seedling.4. The recovery growth of the seedlings treated as above was further studied after the draining water. The results showed that most of the treatment could reduce the membrane permeability of the leaves and increase the content of water, chlorophyll and three osmotic substances (soluble sugar, soluble protein, free proline) and the root activity. Additionally, a part of treatments could enhance the activity of POD and CAT and reduce MDA content. All the treatments could promote the recovery growth, and 0.1 mg/L 6-BA had the best effect.5. The effects of the three regulators on the seedling growth and the recovery growth after the waterlogging stress treatment were studied to sift out the most effective regulator and the corresponding concentration. The results showed: (1) All three regulators could improve the waterlogging resistance and accelerate the recovery growth of the seedling. However, the effect of the same treatment on the same indexes of different experimental materials was different. The effect of the same treatment on the different indexes of the same experimental materials was different. (2) SA, 6-BA and BR had significant influence at the concentration of 250-500μmol / L, 0.1-1 mg/L and 0.01-0.1mg/L concentration, respectively. Based on the comprehensive factors and results, 0.1 mg / L 6-BA was considered as the optimal regulator on adjusting the growth of the seedling of the rape under waterlogging stress or the recovery growth after the draining water.6. The mechanism that the three plant growth regulators could raise the resistance of the oilseed seedling against waterlogging stress was groped. The improvement was realized through reducing the root damage from waterlogging stress, through retaining the high water content and photosynthesis processing, through increasing the osmotic substances and stabilizing the metabolism. It has little relation with the activity of three membrane protective enzymes (SOD,POD,CAT). In addition, most treatment could accelerate the recovery growth through increasing the activity of POD and CAT and declining the content of MDA. |
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