Study On Physiological Characteristics Of Drought Resistance On Malus Sieversii (Ledeb.) Rome.

In this paper,making Malus sieversii as research object,through studying photosynthetic physiology, osmoregulation substance and balance of active oxygen of Malus sieversii under three soil moisture treatments(soil relative water content 70-75%,50-55%,30-35%,respectively)and different treatment time,to discuss the effects of them under water stress and adaptive mechanism to water stress of Malus sieversii.The results were summarized as follows:1. Under the normal soil moisture treatment(CK),LSP of Malus sieversii and check variety Malus robusta was 1550μmol·m-2·s-1 and 1500μmol·m-2·s-1,LCP of them was 30.32μmol·m-2·s-1 and 44.13μmol·m-2·s-1,CE of them was 0.048 mol·m-2·s-1 and 0.028mol·m-2·s-1,it was confirmed that the light ecological adaptability and availability of CO2 of Malus sieversii were better than Malus robusta.Amax of Malus sieversii and Malus robusta was 20.64μmolCO2·m-2·s-1 and 9.40μmolCO2·m-2·s-1,it showed that Malus sieversii had the better physiological basis of dry matter accumulation,and that laid a material foundation for plants on growth and development and adverse-resistant characteristics.2. Pn of Malus sieversii and Malus robusta depressed gradually with increasing in water stress at different treatment time in the same environmental factors,the best adaptive intensity and CO2 density,the same air temperature and humidity.Pn of Malus sieversii and Malus robusta were extremely significant compared with CK under severe drought on the 30th day,it decreased by 62.62% and 81.09% compared with CK.Pn of Malus sieversii was higher than Malus robusta under three soil moisture treatments.3. The daily progress pattern of Malus sieversii Pn was a nontypical double peak pattern under control and moderate drought on the 16th day,and the drop of Malus sieversii Pn was controlled by stomata factor.The daily progress pattern of Malus sieversii Pn was the serious midday depression pattern under severe drought,and the drop of Malus sieversii Pn was controlled by non-stomata factor.The daily progress pattern of Malus robusta Pn was the serious midday depression pattern under three soil moisture treatments,and the drop of Malus robusta Pn was controlled by non-stomata factor.Pn and WUE of Malus sieversii on daily average value were higher than Malus robusta under three soil moisture treatments.4. Fo of Malus sieversii and Malus robusta increased by 8.36% and 52.93% compared with CK under severe drought on the 28th day,it showed that degree of inhibition of Malus robusta was worse.Fm of Malus sieversii and Malus robusta decreased by 3.69% and 5.88% compared with CK under severe drought,Fv/Fm of Malus sieversii and Malus robusta was 0.78 and 0.68,it was confirmed that degree of photo inhibition of Malus robusta was worse either.Fm and Fv/Fm of them showed no significant difference compared with CK after rewatered,it proved that photo inhibition was caused by reversible inactivation of reaction center.5. The relative permeability of cytomembrane and MDA content of Malus sieversii and Malus robusta increased with increases in water stress.They kept normal physiological activities through osmoregulation substance and protective enzyme lessening injury.It was later that cytomembrane of Malus sieversii was damaged and membrane lipid peroxidation than Malus robusta. Relative permeability of cytomembrane of Malus sieversii and Malus robusta increased by 35.21% and 38.33% compared with CK,MDA content of them increased by 32.86% and 49.54% compared with CK,it showed that the damage degree of Malus sieversii was lower,and recovery effect was better after rewatered than Malus robusta.It was confirmed that adaptability to water stress of Malus sieversii was better than Malus robusta.