| Studies on the germination and drought-resistance physiological mechanism inseabuck thorn under water deficit situationPostgraduate: Li lixia Tutor: Prof Liang zongsuo; Prof Zhang jishu(College of Life Science, Northwest Sci-tech University of Agriculture and Foresty ,Yangling,Shaanxi Province ,712100)Various physiological index and mechanism of seabuck thorn in two continuous growth cycle were studied with pot-cultured seedlings, which included effect of soil moisture of and wind speed on nursery stock and survival rate of one-year old seabuck thorn seedlings in sprout period ;the relationship among water content,endogenous hormone and sprout rate of two-year old seabuck thorn in dormancy stage and followed sprout period ; the effect of spraying exogenous GA3 in critical time being researched at the same time ; the growth and water use characteristics and the possible drought tolerance of seabuck thorn seedlings. We expected to discover the critical factor affected sprout of seabuck thorn seedlings and inquire into the water need regularity and drought resistance. These results provided scientific basis for the foster of young growth of seabuck thorn and anti-drought afforestation.The results are as follows:1. Different soil water content had obvious effect on water content,water potential and survival rate of one-year old seabuck thorn seedlings . Compared to higher level soil water content, lower soil level (12%) caused seedlings water content and water potential decreased evidently ,thereby the survival rate reduced .The effect of wind speed varied with the soil water content .When the soil water content was high, two kinds of wind speed had not different effect on the seedlings water content and survival rate. If soil water content was lower than 14.5%,wind speed in 6m/s led to the seedlings water content not reaching 1.2(on the basis of dry weight) ,water potential dropping to -2.6MPa and survival rate was only 26%. Even if seedlings can survival ,whose young shoot grew slowly. On the contrary , seabuck thorn seedlings can maintain higher water content and had a higher survival rate in 54% under the smaller wind speed(3m/s). So, the effective method of cutting out a section of stem or covering up the seedlings with earth should be adopted in afforestation ,in case of survival rate being decreased and growth being restrained due to seedlings′ transpiration too much.2. The relationship among water content,endogenous hormone and sprout rate of two years old china sea buckthorn under soil water stress. The effect of spraying exogenous GA3 in critical time was also researched. Water content and endogenous GA3 decreased due to water stress , in the meantime endogenous ABA increased evidently during dormancy stage in winter and sprout period in spring, which lead to the ratio of GA1/3/ABA fell and reached threshold value later. Seedlings under serious water deficit sprouted 25 days later compared to that of control and grew slowly after sprout. Sprout date of seedlings under medium water deficit was postponed about 10 days and growth after sprout was limited slightly. Spraying exogenous 80mg/L GA3 solution can increase endogenous GA1/3 and GA1/3/ABA of sea buckthorn with ABA content declining under serious water deficit, so sprout date and growth was promoted effectively. The method is simple and convenient and have an good effect.3. The research on water relations of seabuck thorn seedlings showed that: Transpiration rate (Tr) declined with the deepening of soil water stress, while the diurnal change of Tr had little change. They all displayed parabolic shape, which peak value was at 11:00. The decreasing range of water content and water potential was smller, and leaf growth rate of side shoot and photosynthesis rate (Pn) in a higher level under light stress and medium water stress, which showed the typical physiological character belonging to drought-enduring plant. Serious soil water stress made above index fell remarkably and 33.3% seabuck thorn seedlings died after long te... |
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