The Response To Six Species Or Varieties Of Hippophae Rhamnoides Under Drought Stress Conditions

Hippophae rhamnoides is a kind of Native Tree Species which are widely distributed in Northern China, the ecological benefit, social benefit and economic benefit are significant. With the deep research of Sea Buckthorn, the development and utilization of Sea Buckhorn Resource has drawn more and more attention of the whole society. But the current researches about Hippophae rhamnoidesare mainly focused on the ecological benefit, social benefit and economic benefit of Hippophae rhamnoides, the studies on the adaptability of Hippophae rhamnoides under adversity stress are few, especially the change law of physiological and biochemical index about different varieties of Hippophae rhamnoides under drought stress conditions need further study.Based on the above actuality, this paper select six species or varieties of Hippophae rhamnoides, that is Hippophae sinensis, LIAO FU 1, LIAO FU 2, HUN JIN, CHENG SE, QI JI, determine the change of photosynthetic rate, transpiration rate, leaf water content, critical saturation deficit, chlorophyll content, malondialdehyde(MDA) content, dissociative proline content, SOD activity, POD activity, cell membrane permeability under drought stress conditions. We also evaluate the drought-resistant ability using Membership Function Method and Principal Component Analysis, and classify the six species or varieties of Hippophae rhamnoides by using Clustering Analysis. According to the above research, we get the conclusions as follows:①The photosynthetic rate and transpiration rate of six species or varieties of Hippophae rhamnoides have obvious diurnal change. During early stage of stress in June, each variety's diurnal change of photosynthetic rate was double peak curve and a midday depression appeared. The photosynthetic rate reached two peaks at 11:00 and 15:00, and decreased to the lowest at 13:00. The change of transpiration rate was single peak type except CHENG SE, the peak values appeared at 11:00.Under drought stress, the photosynthetic rate and transpiration rate of each variety both decreased. The diurnal change of photosynthetic rate of LIAO FU 1, QI JI, HUN JIN, Hippophae sinensis was double peak curve, while LIAO FU 2 and CHENG SE was single peak type and the peak values appeared at 11:00. The diurnal change of transpiration rate of each variety was double peak curve, which reached two peaks at 11:00 and 15:00, and decreased to the lowest at 13:00. The photosynthetic rate and transpiration rate of LIAO FU 1 and LIAO FU 2 was the highest, while the HUN JIN was the lowest among six species or varieties.②As the drought stress was strengthening, the leaf water content of each variety decreased, and the critical saturation deficit increased. Under the stress, the leaf water content of all varieties was stable, maintaining at 46.68%~69.34%; the leaf drought content of HUN JIN, CHENG SE, QI JI is lower, and LIAO FU 2 is the highest. The critical saturation deficit of Hippophae sinensis is the highest, and QI JI is the lowest in the later stage, which indicates that it is easily affected by drought stress.③T he Chlorophyll a, Chlorophyll b of six species or varieties of Hippophae rhamnoides decreased with the drought stress aggravated; the Carotenoid content increased firstly then decreased afterwards. The above pigment of LIAO FU 1 is the highest and CHENG SE is the lowest.④The dissociative proline content of each variety increased continuously. The dissociative proline content of LIAO FU 1, LIAO FU 2, Hippophae sinensis is higher.⑤As the degree of drought stress was strengthening, the trend of SOD activity and POD activity are similar, which rises firstly and falls later. During the whole process, the SOD activity and POD activity of LIAO FU 1, LIAO FU 2, Hippophae sinensis is high while QI JI is weak. The SOD activity of LIAO FU 1, LIAO FU 2, Hippophae sinensis decreased slowly in the late stage, which indicates that they have strong ability of maintaining the SOD activity, and the drought resistant ability is better.⑥During the whole process, the malondialdehyde (MDA) content of all varieties accumulates with different degrees, and the increase amplitude of MDA content became larger with the strengthening of osmotic stress. It shows that the injury degree of membrane system was gradually strengthened. The MDA content of CHENG SE, HUN JIN, QI JI maintains a higher level, and the content of LIAO FU 1 and LIAO FU 2 is lower, showing that the injury degree of membrane system of this two varieties is gentle, and the drought resistant ability is stronger.⑦With strengthening of drought stress, the cell membrane permeability of all varieties increased continuously, the order of cell membrane permeability is ranged from low to high as follows: LIAO FU 2, LIAO FU 1, Hippophae sinensis, QI JI, HUN JIN, CHENG SE, this phenomenon shows that the drought resistance of LIAO FU 2 is the best, while the CHENG SE is the worst as the injury degree is the most serious.⑧I n this study, most indexes of all varieties under drought stress conditions exhibits that the index's value are close at the beginning of stress stage, and the amplitude and diversity became greater with the strengthening of stress. It indicates that the indexes of Hippophae rhamnoides change little at minor water aridity due to its adaptable function; but once the stress degree exceeds the limit, it will aggravate the injury degree. So the change becomes greater as the stress degree become severe. ⑨Using Principal Component Analysis and Membership Function Method , we came to the conclusion that the drought resistance of six cultivars is: LIAO FU 2 > LIAO FU 1 > Hippophae sinensis > CHENG SE > HUN JIN > QI JI. By using Cluster Analysis, the six species or varieties of Hippophae rhamnoides can be divided into two types: CategoryⅠwas LIAO FU 1, LIAO FU 2, Hippophae sinensis, and CategoryⅡwas CHENG SE, HUN JIN, QI JI. From the cluster analysis pedigree diagram, we can know that the drought resistance of LIAO FU 1 and LIAO FU 2 is very close, the drought resistance of Hippophae sinensis is worse than LIAO FU 1 and LIAO FU 2, but better than the other three varieties.Meanwhile, we discuss the selection of drought resistance evaluation index, the choice of drought resistance assessment method and fine varieties breeding of Hippophae rhamnoides, put forward that Drought Resistance Appraisement Index System should select the index follow the principle of multiple index, multi-angle, wide scope; in order to ensure the evaluation method is reasonable and the result is reliable, the drought resistance assessment method should strengthen the consideration of correlation coefficient between the indexes, and screened out the representative and important index, then evaluate them. The fine varieties breeding of Hippophae rhamnoides should comprehensively consider the all kinds of benefit, fruit quality, stress adaptability, so to reach stable and high yield and create better benefit.In the last part of this paper, we look into the future the utilization prospects of Hippophae rhamnoides.