Study On Effccts Of Water Stress On Photosynthesis And Physiologieal Charaeteristics Of Three Olive Varieties

In this paper,3varieties of olive trees Pichal, Frantoio and Ezhi8were taken as test materials, according to relative soil water content,3varieties of olive trees were divided into3groups:the control group (CK, relative soil water content were85%FC), the moderate water stress group (MW, relative soil water content were55%FC), the serious water stress group (SW, relative soil water content were25%FC), respectively,2water stress groups were rewater after20days (RMW, moderate water stress group rewater; RSW, serious water stress group rewater), the relative soil water content was reached the level of CK. The response characteristics of photosynthetic, Physiological and biochemical of olive trees were studied under water stress, the effects of photosynthetic and biochemical characteristic and the different of adaptability between3olive varieties under water stress were studied. The main results were as follows:(1). Maximum net photosynthetic rate(Pnmax), apparent photosynthetic quantum yield (AQY), light saturation point (LSP) and dark respiration rate(RD) declined, light compensation point (LSP) increased under water stress, AQY had not significant difference (P>0.01) among them. Under all the water treatments, the indexes of nmax, AQY, LSP were highest and LCP was lowest in Frantoio, while the indexes of nmax, AQY, LSP, RD were lowest and LCP was highest in Ezhi8, after rewater, all the indexes of3olive varieties gained some recovery, but the degree of restoration had some different between3olive varieties, RMW and RSW of Frantoio had not significant difference (P>0.01) compared with CK, achieved the best recovery; all the indexes of RMW and RSW of Pichal recovered to the level of CK and had not significant difference (P>0.01) except for nmax in RSW, which just could reach the level of MW; all the indexes of RMW of Ezhi8recovered to the level of CK but Pnmax (<0.01) while Pnmax and LSP of RSW just reached the level of MW, which achieved the poorest recovery.(2). The effect of gas exchange of3olive varieties had significant influence under water stress. net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (GG), intercellular CO2concentration (C1) of the leaf reduced with the high intensively water stress, and stomatal limitation value (LS) and water use efficiency (WUE) rose. moderate water stress effected the photo synthetic rate by stomatal limitation, but the nonstomatal limitation was predominant under serious water stress.(3). Water stress influenced photosynthetic pigment content obviously. The contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid were reduced, Chla/Chlb and Chl/Car were increased with the high intensively water stress. photosynthetic pigment content of olive leaves was sensitive to serious water stress. After rewater, the contents of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid of RMW and RSW of Frantoio and Pichal recovered to the level of CK, the photosynthetic pigment content of Ezhi8completely recovered just in the condition of RMW, while the significant difference (P>0.01) between RSW and CK, that showed rewater helped the photosynthetic pigment content of olive leaves to recover, but Frantoio and Pichal achieved better than Ezhi8.(4). The content of Proline (Pro) and Soluble sugar (SS) of olive leaves increased with the high intensively water stress, the highest content of Pro and SS of Pichal Frantoio and Ezhi8showed in SW, were49.72μg-g-1FW,55.81μg·g--FW,27.05μg·g-1FW and24.61mg-g-1FW,22.51mg-g-1FW,28.73mg-g-1FW, respectively. Pro was the main substance of olive to resist water stress. Frantoio and Pichal showed better than Ezhi8.(5). Superoxide dismutase (SOD) and Peroxidase (POD) activity of3olive varieties were highest under moderate water stress, and SOD and POD activity were inhibited, but protective enzyme activity of Frantoio was always higher than Pichal and Ezhi8. The content of Malondialdehyde (MDA) of olive leaves increased with the high intensively water stress, the lowest increase amplitude was Frantoio, and highest one was Ezhi8. In this study, SOD and POD activity correlated with the content of MDA, higher SOD and POD activity were beneficial to inhibit the synthesis of MDA.According to study the photosynthetic, Physiological and biochemical of3varieties of olive trees Pichal, Frantoio and Ezhi8, photosynthesis was weakened under water stress, osmotic adjustment and antioxidation system could reduce the damage and enhance the adaptation. Analysisd the effect of3varieties of olive trees under water stress and rewater, indicated that the adaptation of Frantoio to water stress was strongerset, Pichal took the second place, Ezhi8was the poorest.