Study On Olive Drought Resistance Physiology And Its Regulation

Olive(Olea europaea L.) is an oil producing evergreen perennial arbor, its fruit can be squeezed out a kind of high quality cooking oil, the olive oil. Olive has produced significant economic benefits since it was introduced into China, and the cultivated area has enlarged rapidly with time. Bailong river coast is one of the primary suitable districts of olive in China, and olive fruit and oil production has mounted to more than 90% of the total output in China. However, as olive is limited in a particular growth environment and ecological conditions, and olive in Bailong river coast was planted mainly in the poor mountain irrigation areas, the drought stress has become one of the important factors that restrict its the yield and the plant district. The study about the olive drought resistance physiology and relevant technology are still scarce nowadays, so this paper studied the following four aspects:The first part of this study aimed at using detached leaves of three olive cultivars of Olea europaea varieties(?Gordal‘, ?Chenggu32‘ and ?Frantoio‘) as experimental materials, we determined their physiological and biochemical indexes, to explore the mechanism on drought resistance of different olive varieties under 30% PEG stress. The results showed that:(1) With the time of osmotic stress prolonged, the water and chlorophyll contents in detached leaves of different olive varieties decreased, while the relative electrolytic leakage and MDA content increased significantly, the result indicated that, the osmotic stress caused deterioration of water conditions, decomposition of chlorophyll, aggravation of lipid peroxidation and damage of cell membrane of the leaves; meanwhile, relative content of bound water and free water, O2-. producing rate, SOD activity and regulatory substances in leaves of three olive varieties showed a rising trend.(2)Inter-species comparison, with the time of osmotic stress prolonged, MDA content of ?Frantoio‘ leaves was lower than that of ?Gordal‘ and higher than that of ?Chenggu32‘. In the same period, changes on the content of bound water and free water, superoxide anion production rate, SOD activity of different species leaves showed similar performance. In conclusion, the results indicated that the drought resistance of the three olive varieties was ?Chenggu32‘> ?Frantoio‘ > ?Gordal‘; furthermore, higher ratio of bound water content/free ware content, less O2-. producing rate, higher SOD activity and more regulatory substances of ?Chenggu32‘ under the osmotic stress can guarante the leaves of ?Chenggu32‘ had the strongest ability of osmoregulation and the strongest ability to endure dehydration and lipid-peroxidation under the osmotic stress, so the drought resistance of ?Chenggu32‘ was better than that of ?Gordal‘ and ?Frantoio‘.The second part of this study based on olive(variety Frantoio) annual seedlings as test materials, spraying 66.7 mg/L(PP333) on the surface of olive seedling leaves, each spraying quantity to 100 m L, and setting a contrast respectively(spraying the same amount of distilled water), then stop water, drought stress were taken 0, 2, and 7 days of olive leaves for the determination of the physiological and biochemical indexes and comparative analysis, in order to explore the influences of PP333 on olive seedling leaves‘ cell membrane protective systems under drought stress were studied in this paper. The results showed that cell membrane was damaged significantly under drought stress(stop watering 7d), but spraying PP333 on the olive seedling leaves significantly reduced the damage degree of the cell membrane, the data showed that its cell membrane‘s stability index was 41.5% higher than the contrast(the same amount of distilled water sprayed on the leaves) after stop watering 7d. The results also showed that spraying PP333 on olive seedling leaves relatively reduced the reducing range of chlorophyll content and carotenoid content, increased the content of proline and soluble sugar significantly, further improved the activity of SOD, POD and CAT, inhibited the increasing range of MDA content, O2-. producing rate and H2O2 content, and even improved the content of the two kinds of important antioxidants(Vc and reduced glutathione) under the drought stress significantly. So it can be concluded that through improving the activity of antioxidant enzymes, enhancing the content of antioxidants and osmotic regulation substances, reducing the decline of photosynthetic pigment content and the accumulation of active oxygen and free radicals, spraying PP333 on the olive seedling leaves promoted the protection on the cell membranes of olive seedling leaves under the drought stress.The third part discussed the resistance physiology and rhizosphere and soil environmental factors by soil scarifying of olive under drought stress. By measuring the physical and chemical index of rhizosphere soil, soil enzyme activity and soil microorganism content and the resistance of the olive leaf physiological indicators between soil scarifying and not soil scarifying, comparative analysis, in order to explore the soil scarifying of olive rhizosphere soil microenvironment and scarification improve olive physiological mechanism of drought resistance, to improve the drought resistance of olive production and to provide theoretical support. The results showed that: with the irrigation insufficiency caused by drought stress level increasing, olive leaf super oxygen anion generating rate, MDA and H2O2 content increased significantly, it suggested that drought stress can cause olive leaves oxidation. But under the condition of same irrigation, soil scarifying reduced the oxidation caused by drought stress and improved the leaves chlorophyll, carotenoid content and membrane stability index; The serious water shortage,(water-2) olive leaves, after soil scarifying SOD activity, POD activity, CAT activity, Vc content and glutathione content reduced, less pulverizing blade respectively increased by 1.00%, 20.96%, 54.50%, 17.82% and 20.02%, and increased the olive antioxidant enzyme activity and the enzymes of antioxidant substances content have resisted drought caused by oxidative stress; soil scarifying treatment also increased olive leaf soluble sugar and proline content under drought stress, it also has a role in improving drought resistance.The results also showed that soil scarifying treatment improved the olive rhizosphere soil water content and root activity, reduced the soil p H value; Under the condition of normal irrigation(water-CK), vehicle processing less scarification olive rhizosphere soil fertility of alkaline phosphatase, urease, invertase and catalase activity increased by 64.37%, 193.49%, 193.49% and 64.37% respectively, this shows that the soil scarifying can improve the effectiveness of the soil fertility; Soil scarifying also significantly increased the number of rhizosphere bacteria, fungi and actinomycetes, and these changes in biological and non-biological environmental factor, mineral nutrition and moisture condition have positive role for olive, especially in the case of the drought stress caused by insufficient irrigation. Visible, on the one hand, soil scarifying improved the rhizosphere microenvironment of olive under drought stress, on the other hand, strengthened the olive leaves enzyme peace-making non enzymatic antioxidant system, thus effectively improved the resistance of olive under drought stress as a whole.In fact, after soil scarifying ground surface soil is relatively dry, but due to soil watered by capillary action to prevent deep loss, relatively improved the rhizosphere soil moisture conditions, especially the ripper can influence the rhizosphere microorganisms and relative enzyme activity of soil fertility, which may be related to the reason that soil scarify is promoted the rhizosphere ventilation conditions. Visible soil scarifying improved soil water supply and improved the resistance of the olive physiology and it had a positive and effective role.The fourth part studied the 10 year old olive plants as experimental material, by controlling the soil water content of intercropping and interplanting bahia grass or not processed, the determination of olive rhizosphere soil physical and chemical indexes, soil fertility relative enzyme activity, microbial content and leaf physiological and biochemical indicators, comparative analysis, discussed the intercropping bahia grass and drought stress on the rhizosphere microenvironment and blade with a high resistance physiological effects. The results showed that with the degree of drought stress, olive leaf chlorophyll, carotenoid content and cell membrane stability index fell, the ultra oxygen anion producing rate, MDA content and H2O2 content raised, this showed that the drought stress caused the olive leaf oxidative stress; After intercropping bahia grass, on the one hand, the olive chlorophyll and carotenoid content and cell membrane stability index were improved and the super oxygen anion generating rate, the rise of MDA content and H2O2 content were inhibited, the soluble sugar, proline, Vc were increased and glutathione levels were reduced, the SOD, POD and CAT activity were enhanced. On the other hand, the olive root activity, soil organic matter content, soil moisture, soil enzyme activity and soil microorganism quantity were increased, the p H value of soil was reduced. Visible intercropping bahia grass can improve olive soil microenvironment and its antioxidant capacity, thus enhanced the drought resistance of the olive on the whole.To sum up, under 30% PEG osmotic stress solution, ’Chenggu 32’ leaves have stronger ability to resist dehydration, oxidation resistance and osmotic regulation ability, thus in overall stronger resistance to osmotic stress. Foliar spraying PP333 reduced the olive leaf chlorophyll, carotenoid content decreased, the proline and soluble sugar content, SOD, POD and CAT activity and MDA content, O2-. producing rate significantly increased and the amplitude of H2O2 content increased, Vc content improved and glutathione reduced. That two important contents of antioxidants effectively reduced the injuries of the olive caused by the drought stress. After treated with digging, interplanting bahia grass were significantly improved the resistance physiology of olive leaves and olive rhizosphere microenvironment, so this provided a technical support for the healthy development of olive industry, and illuminates the physiology and regulatory mechanism of olive under drought stress.