| Drought stress is one of the important limiting factors for turf establishment, so the research on the drought resistance of turf has always been an important topic in the research of turf grass. Many plant hormones play an important role in the process of drought resistance in plants, This study investigate the effects of gibberellin alleviating on seed germination and seedling growth of tall fescue(Festuca arundinacea)within drought stress. After soaked the malondialdehyde, conductivity, seedling growth and seed germination were determined in the experiment. The effects of abscisic acid(ABA)and brassinolide(BR) on the physiological and photosynthetic characteristics of tall fescue were studied under drought conditions.1、The first part is aimed to investigate the effects of gibberellin alleviating on seed germination and seedling growth of tall fescue within drought stress. First, seeds were soaked in 5 gibberellin concentration levels(0,100, 200, 300, 400 mg/L). After soaking the germination experiment was conducted under 5 polyethylene glycol(PEG) levels(0%, 5%, 10%, 15%, 20%). After soaked the malondialdehyde, conductivity, seedling growth and seed germination were determined in the experiment. After 2 months growth of tall fescue, under the normal irrigation, moderate and severe drought stress, foliar application of H2 O, 0.4mg/L BR, 0.8mg/L BR, 10mg/LABA, 20mg/L ABA, complex hormones BR*ABA(0.4 mg/LBR and 10 mg/LABA) were used to alleviate drought. Relative water content, MDA, proline and antioxidant enzymes activity, photosynthetic characteristics and other indicators were determined under different treatments of tall fescue.1、Results showed that the conductivity of 0 and 100 mg/L gibberellin soaked was significantly higher than(P≤0.05)that of the other three levels. While the malondialdehyde was significantly lower than(P≤0.05)that of other three levels. The inhibitory effects increased obviously with the increasing of PEG concentrations. When the PEG concentration is higher than 15%, germination rate, root and bud length decreased obviously. Compared with the 0 mg/L gibberellin soaking, germination energy of 100 mg/L soaked increased 47.06%, 37.33% and the germination rate increased 19.46%, 16.95% under 5% and 10% PEG, Root length of 200 mg/L gibberellin soaked increased 53.26%, 30.12% and bud length increased 79.87%,50.75% under 5% and 10% PEG. The alleviating of gibberellin weakened with the increasing PEG stress. In addition, the inhibition of PEG stress on the root was stronger than bud, but root-bud ratio become decreased obviously after gibberellin soaking.2、The results showed that the relative water content, proline and soluble protein were the highest in the treatment of BR*ABA under moderate and severe drought conditions, while the MDA and relative conductivity were the lowest. The proline content under high concentration of BR was significantly higher than that of(P≤0.05)low concentration. There was no significant difference of water content, MDA and proline between high and low concentrations of BR under severe drought, and relative water content and soluble protein of high concentration of ABA was significantly higher than that of(P≤0.05)BR and low concentration of ABA treatment, while MDA and relative conductivity was significantly lower than that of(P≤0.05)BR and low concentration of ABA treatment.3、The trend of superoxide dismutase(SOD), peroxidase(POD) and catalase(CAT) activity with drought stress aggravated increased first and then decreased. high ABA and BR of peroxidase(POD) and catalase(CAT) was significantly higher than that(P≤0.05)of low concentration under moderate drought stress. Only the CAT and POD of 20mg/L ABA were significantly higher than(P≤0.05)low ABA under severe drought, while there was no significant difference between the high and low BR. the treatment of 20mg/L ABA and BR*ABA under moderate and severe drought was significantly higher than that of(P≤0.05)normal irrigation.4、Under moderate and severe stress, the photosynthetic rate and stomatal conductance of BR*ABA and 0.8 mg/LBR was the highest, and significantly higher than that of ABA and non hormone treatment. Transpiration rate of BR*ABA, 0.4 mg/LBR and 0.8 mg/LBR were significantly lower than(P≤0.05)that of ABA and normal irrigation treatment.In a summary, the optimum gibberellin concentration for the promotion of tall fescue seed germination, seedling growth and mitigation of drought stress is 100-200 mg/L. The alleviating effect of BR*ABA(0.4 mg/LBR and 10 mg/LABA)on physiology, photosynthesis and antioxidant enzymes was the best under both severe and moderate droughts, the ABA and BR stack effect. The effect of ABA on physiological Indexes under drought stress was better than that of BR, while the effect of BR on photosynthesis was better than ABA. |
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