Effects Of Plant Growth Regulators On Drought Resistance Of Flue-Cured Tobacco

From 2013 to 2014 the effects of plant growth regulators on flue-cured tobacco (Nicotiana tabacum L.) morphology changes had been studied, water status and protective enzyme activity and the influence of osmotic regulation substances under drought stress, so as to screen out plant growth regulators that can enhance drought adaptability of flue-cured tobacco and the appropriate concentration. The test results are as follows:1. Under drought stress, the effects of these plant growth regulators with different concentrations on the growth and development of middle leaf are different. The effects of TDZ and 6-BA on leaf length, width and leaf area of flue-cured tobacco are significant. The processing of leaf length, width and leaf area with ABA 40 mg/L and 60 mg/L treatment can be significant, while only 60 mg/L of GA3 have significant effect on leaf length, width and leaf area.2. During the whole drought stress, the effects of plant growth regulators with different concentrations on the height of flue-cured tobacco are different. GA3 has significant or extremely significant effect on plant height.60mg/LABA treatment in the middle of the drought has significant effect on plant height, as the time longer, the effect is not significant. The effect of TDZ on plant height in the whole drought stress isn’t significant.200μmol/L-300μmol/L 6-BA has a significant effect on plant height in the middle of the drought stress, as the processing time is longer, the effect is not significant.3. Under drought stress, spraying different concentrations plant growth regulators, the leaf relative water content (RWC) of flue-cured tobacco is different. Water retention ability of plant was stronger under the treatment 200uM of TDZ, the RWC drop was 59.28% of the control; The concentration 200uM of 6-BA had a better effect on water retention ability of tobacco than 200uM and 300uM, but the RWC drop could reach to 80.33% of the drop of control’s; among three concentration of ABA treatment, RWC changed more gently under 60mg/l, and the drop was 50.84% of control’s; RWC drop could be 72.09% of the control under the treatment of 60mg/l GA3, water retention ability was slightly higher than other concentrations of GA3.4. Under drought stress, spraying different concentrations of plant growth regulators, activity of protective enzyme system of tobacco leaf has different change rule. SOD activity rising at the beginning of spraying 6-BA and GA3, after a brief of drop the SOD activity rise again; under the treatment of TDZ and ABA, SOD activity falling in the whole drought stress process, this trend is more obvious when the drought is more serious. Spraying tobacco leaves with 6-BA and GA3, the POD activity have the same variation trend:they rise at the beginning then they will fall to a low level; the activity of POD change in the same way after Spraying TDZ and ABA, "rise-down-rise. Sprayed 6-BA, ABA, GA3, the activity of CAT showed the trend dropping firstly and then increased with the drought intensity’s increasing and time’s going, and the drought intensity was higher, the trend was more serious, however the CAT activity showed the trend "rise-down-rise".5. Under drought stress, different concentrations of plant growth regulators can reduce the content of MDA, which is trademark material of membrane lipid peroxide, they can also enhance the content of soluble protein at different levels. Under ABA treatment the MDA content showed the trend rising firstly and then decreased, spraying tobacco leaves with TDZ,6-BA and GA3, the MDA content showed the trend "rise-down-rise", and the drought intensity was higher, the trend was more serious. Both four kinds of growth regulators can alleviate the level of membrane lipid peroxide. And four growth regulators can enhance the content of soluble protein at beginning of drought stress, and then dropped down. The protein content increased sharply in the early of drought stress, but the levels of ascension can be very different under the treatment of these regulators, however as the drought continued, protein content begun to decline and the difference of protein content decreased. Visible, both the four kinds of plant growth regulators can protect membrane lipid at different levels.6. Comprehensively analyzed these parameters by subordinate function we concluded that:the effect size of TDZ treatment on flue-cured tobacco drought resistance enhancement order for 300uM>200uM>100uM, the effect size of 6-BA treatment on flue-cured tobacco drought-resistant ability enhancement order for 300uM>200uM>100uM, the effect size of ABA treatment on flue-cured tobacco drought-resistant ability enhancement order for 60mg/l>40mg/1>20mg/l, the effect size of GA treatment on flue-cured tobacco drought-resistant ability enhancement order for 60mg/1>40mg/1>20mg/1. show that the concentration of TDZ at 100uM～300uM,6-BA at 100uM-300uM, ABA at 20mg/l～40mg/l, GA3 at 20mg/l～60mg/l, the higher the concentration of these regulators, the stronger drought resistance flue-cured tobacco have.