Effects Of Water Stress On Physiology And Photosynthetic Characteristics In Leaves Of Grape

In order to explore the physiological metabolism characteristics of grape under water deficits, thus provide a theoretical basis for the study of grape drought resistance cultivation. Different concentration PEG-6000was used to simulate water stress. Four water stress levels was setted in this experiment which included contrast0%(CK), light stress5%(T1), moderate stress10%(T2), severe stress15%(T3), Each treatment had five replicates and each had two seedlings. Physiological characteristics of grape seedlings was recorded, including water metabolism indicators:RWC, WSD, freedom-water, bound-water and ratio of freedom-water and bound-water; osmotic metabolism indexs:proline content, relative conductivity; photosynthetic parameters and fluorescence parameters:net photosynthetic rate(Pn), the transpiration rate(Tr), the leaf stomatal conductance(Gs), the intercellular CO2concentration(Ci), the original fluorescence (Fo), the maximum fluorescence(Fm), the variable fluorescence(Fv), light energy transformation efficiency of PSII(Fv/Fm), electron transport rate(ETR) and actual photochemical efficiency of PSII(Yield); the change of Carotenoids and abscisic acid content. Each kind of physiological characteristics indicators of grape was analyzed under different water stress levels The results were as follows:1. Before84hours of water stress time, the T1grape seedlings of Flame seedless and Chardonnays’RWC and freedom-water decreased slowly, but bound-water increased slowly. RWC, freedom-water of the T2and T3kept decreasing with the increasing of water stress time and; got the minimun value at the stress time of108hours. While the maximum value of,bound-water was gotten at the time of60hours and36hours. The ratio of the freedom-water and bound water of T1, T2and T3showed a trend of rise-fall-rise.2The root activity of Flame and Chardonnay grape seedlings T1got the maximum value at the60hours, later started to decrease. The root acitivity of T1was always higher than CK. T2and T3got the maximum value at the stress time of36hours, then decreased rapidly, and got the minimum value at the108hours.3The relative conductivity of Flame seedless and Chardonnay T1kept increasing slowly. The relative conductivity of,T2and T3increased rapidly and got the maximum value at the108hours. The proline content of T1kept increasing rapidly after36hours of stress time while T2and T3kept inceasing rapidly at the beginning and got the maximum value at the108hours.4The net photosynthetic rate(Pn), transpiration rate(Tr), leaf stomatal conductance(Gs) and intercellular CO2concentration(Ci) of Flame seedless and charonnay seedlings decreased significantly with the stress time increasing under each water stress levels, and got mimimum value at the108hours. The decrease amplitude represented T3>T2>T1. Water use efficiency(WUE) and stomatal limitation(Ls) significantly increased, firstly, T1got maximal value at the60hours, but T2and T3got maximal value at the84hours; the original fluorescence(Fo)and non-photochemical quenching(qNP) obviously increased, the variable fluorescence(Fv), maximal fluorescence(Fm), light energy transformation efficiency of PSII(Fv/Fm), activity potential of PSII(Fv/Fo), electron transport rate(ETR), actual photochemical efficiency of PSII(Yield)and photochemical quenching (qP) obviously decreased.5The carotenoids and Abscisic acid content of T1showed an increasing tendency before36hours of the stress time, later deceased rapidly. But T2decreased slowly before36hours and then decreased rapidly. While the carotenoids of T3was always decreasing rapidly and got the mimimum value at the108hours. Both Charonnays and Flame seedless leaves’abscisic acid content represented an increasing tendency. All of Flame seedless T1, T2and T3got the maximum value at the36hours, then decreased rapidly.The maximum value of charonnay seedlings T1, T2and was gotten at different stress time:T1and T2got the maximum at the84hours, T3got it at the36hours.