Regulating Mechanism Of Exogenous Abscisic Acid On Cropping Obstacles And Aluminum Stress In Trichosanthes Kirilowii Maxim

Trichosanthes kirilowii Maxim. was chose as test materials which cultivated with hydroponics and field cultivation methods respectively. The seedlings will be pretreated with exogenous ABA, then subjected to aluminum stress in the hydroponics. Whereas for those cultivated in the field the seedlings which suffered from the continuous cropping obstacles even beyond three years was sprayed ABA to their roots. Growth development, as well as its defense enzyme activities and physiological indicators in Trichosanthes kirilowii Maxim. was measured and analyzed. The results were summarized as follows:1.Under the condition of cropping obstacle, compared to the control group which doesn’t apply exogenous ABA TO (0 mg/L ABA), the treatment group T1 (2.5 mg/L ABA), T2 (5 mg/L ABA), T3 (7.5 mg/L ABA), T4 (10 mg/L ABA), while showed that their chlorophyll a, chlorophyll b and Asa content were significantly inhibited, soluble sugar, Pro, MDA, and Dasa content increased. With the concentration of exogenous ABA rising, the variation tendency of chlorophyll a, chlorophyll b and Asa content increased at first and then decreased, As for the variation tendency of soluble sugar, Pro, MDA and Dasa content decreased at first and then increased.The results indicated that the low concentrations of exogenous ABA can improve the ability of Trichosanthes kirilowii Maxim, to resist the damage from continuous cropping obstacles, but not with a high concentration.2.Under the condition of aluminum stress, comparing to the control group CK(0 mg/L ABA, Oμmol/L Al3+), root length, root activity, ETR, Fm, Fv/Fm, chlorophyll a content, chlorophyll b content, Asa content and GSH content of the single aluminum treatment group T1(0 mg/L ABA,600μmol/L A13+) significantly reduced The indices recovered with the application of exogenous ABA, but are unable to return to the level of the control group CK. High concentration of ABA, such as T4 (7.5 mg/L ABA,600μmol/L Al3+), T5 (10 mg/L ABA,600μmol/L Al3+) treatment group reduced the root length, root activity, ETR, Fm, Fv/Fm, chlorophyll a content, chlorophyll b content, Asa content and GSH content again, even lower than T1 treatment group. Comparing to CK, showed that F0, soluble sugar content, MDA content, Pro content, H2O2 content, Dasa content of the group T1 increased significantly, but decreased and then rebounded with the increasing of the concentration of exogenous ABA.3.Under the condition of cropping obstacle,the activities of antioxidase SOD, POD, CAT and PPO showed changes with exogenous ABA concentration in peak shape, which is to fall after the rise.The peak of PPO activity occurred in T3 group while other activity peaks happened in T2.In addition, the activities of PAL and APX increased significantly with the exogenous ABA, but inhibition occurs when the concentration of ABA is high. According to the membership function analysis, the capacity to relieve the damage of continuous cropping obstacles with exogenous ABA is:T2> T3> T1> T0> T4 The results show that the concentration of ABA in certain extent can enhance the antioxidant capacity of Trichosanthes kirilowii Maxim. under continuous cropping obstacles to protect plant cells from peroxide damage.4.4.The activities of defense enzyme, SOD, POD, CAT, PAL and APX, in the leaf of Trichosanthes kirilowii Maxim. occurred inhibition significantly under Al stress.With the increase of the concentration of exogenous ABA, the activities ascended firstly and then declined. The results indicate that the exogenous ABA with a certain concentration can alleviate the effects of aluminum stress. According to the membership function analysis and coefficient of aluminum tolerance analysis,the conclusion was drawn that the aluminum tolerance capability is T3 (5 mg/L ABA,600μmol/L Al3+)> T4> T2 (2.5 mg/L ABA,600μmol/L Al3+)> T1> T5.