Comparison Of Drought Resistance Of Nine Camellia Oleifera Clones In Seedling Stage

Camellia oleifera Abel., belonging Theaceae, Camellia perennial woody oil plants, are evergreen small trees or shrubs. Camellia trees adapt to warm and humid surrounding, and are sensitive to cold weather. Since Camellia development, such as buds development, fruit enlargement, grease conversion, in July and August, requires a larger amount of water. Therefore, the rain water is important for Camellia trees. During this time Camellia trees cannot get enough water and leaves turn yellow or even drop, which affect yields of Camellia fruits. The Camellia forest covers a huge area of approximate 400 ha, which is widely distributed in southern China, such as Sichuan, Yunnan, Guangxi, Hunan, Hubei, Jiangxi, Fujian and Taiwan about 18 provinces and more than 1,100 counties. We selected 2-year-old seedlings of Camellia oleifera clones including ’Changlin3’,’Changlin4’,’Changlin8’,’Changlinl8’,’Changlin22’,’Changlin27’, ’Changlin40’,’Changlin53’, and’Changlin59’as experiment materials, through water-controlled method with Camellia planted in potted. We measured the physiological and photosynthetic indexes including active oxygen contents, antioxidant enzyme activities, osmotic substances contents, cell membrane permeability and photosynthetic parameters during the drought. At the same time, the drought resistance was comprehensively evaluated by correlation analysis, principal component analysis and subordinative function. The main results are as follows:1. The reactive oxygen species response of 9 Camellia oleifera varieties under drought stressWith the decrease of soil moisture, O2--and H2O2 contents of 9 Camellia oleifera varieties had always increasing trend. H2O2 contents of Changlin40, Changlin53 and Changlin59 at first rapidly increased drought 15d. After drought 20d O2--production rate of Changlin8, Changlinl8, Changlin27, Changlin53 and Changlin59 fast accelerated. Compared with other O2-·and H2O2 contents of Camellia oleifera varieties, those of Changlin8, Changlin18, Changlin27 and Changlin53 increased significantly.2. The antioxidant enzyme activities response of 9 Camellia oleifera varieties under drought stressDuring drought stress, the activities of SOD and POD increased at first, and then decreased. The antioxidant enzymes activities were highest after drought stress for 15d. However, CAT activities of 9 Camellia oleifera varieties had always increasing trend. Changlin8, Changlinl8, Changlin27 and Changlin40 showed rapid increasing trend, indicating that CAT activities of four Camellia oleifera varieties were more sensitive to drought stress.3. The osmotic substances response of 9 Camellia oleifera varieties under drought stressPro and soluble proteins contents with the drought stress extend showed were increasing trend. After drought 15d, Pro and soluble proteins contents of Changlinl8 rapidly rise. During drought stress, those of Changlin22, Changlin53 and Changlin59 were relatively steady increasing.4. The cell membrane permeability response of 9 Camellia oleifera varieties under drought stressAs the drought stress proceeding, relative electric conductivity and TBARS content were increasing. Compared with relative electric conductivity and TBARS content of other 6 Camellia oleifera varieties, those of Changlin4, Changlinl8, Changlin27 and Changlin53 increased significantly drought 15d.5. The photosynthetic parameters response of 9 Camellia oleifera varieties under drought stressNet photosynthetic rate, stomatal conductance and transpiration rate in leaves of Camellia oleifera were decreased along with stress time. Net photosynthetic rate and stomatal conductance of Camellia oleifera fell dramatically after drought 10d. Those of Changlinl8th decreased more dramatic, while Changlin53 relatively declined more slowly drought 25d. During drought stress, transpiration rate of the control group showed a slow increasing trend, while the transpiration rate of the treatment group decreased along with stress time. After drought 10d transpiration rate of Changlin18 drastically reduced. Drought 25d, transpiration rate of Changlinl8 was only 2.63% of the initial value. During drought 5d, water use efficiency of the control group still stabilized, but water use efficiency turned decreasing after drought 10d. Water use efficiency of 9 Camellia oleifera varieties lower than their initial value drought 25d. Those of Changlin3 Changlin22 and Changlin53 in treatment group had similar trend, at the first section decreased before drought 15d. The water use efficiency of Changlin8 and Changlin40 were always decline along with the stress time.6. Comprehensive assessment of drought resistance in 9 Camellia oleifera varietiesPlant drought resistance is a relative complex and integrative physiological process. There is a certain correlation between the indexes. So they overlap the information provided. At the same time, any single index is difficult to fully reflect the true of plant drought resistance. If these indexes of drought resistance were directly used, it would cause greater deviation. Therefore, the drought resistance of 9 Camellia oleifera varieties should be comprehensively evaluated by correlation analysis, principal component analysis and subordinative function. The order of drought tolerance was ’Changlin59’> ’Changlin22’>’Changlin4’>’Changlin53’ >’Changlin40’>’Changlin8’> ’Changlin3’>’Changlin27’>’Changlin18’.