Study On Introduction And Seedling-breeding Of Rock Elms From America And Its Physiological Characters Under Water-and-salt Stress

This paper overviews the studied statesquo of physiological characteristics for some plants under saltstress and waterstress, based on this ,we proceeded to have the seedling-bred experiment on Ulmus pumila in China, Ulmus thomasii and U. Crassifolia from the United States,under the glasshouse condition three kinds of one-year seedlings were proceeded the plant-potted experiment through salt-and-water control, physiological and biochemical indexs reflecting salt-and-drought resistence were periodically measured, then analyzed, finally synthesized to assess them. 1 .In the course of seedling-bred experiment, three trees above were respectively measured height growth, ground diameter growth, anti-diseases-and-insect pests ability, the ability of outside power-resistence to roots etc.the research showed: the growth amount of ground diameter and the ability of outside power-resistence to roots for one-year Ulmus thomasii and U. Crassifolia outgrew in China, but its height growth and the ability of control to some diseases and insect pest were more interior ,buds sprouting, seed budding,and autumn defoliage time were put off from two to three weeks or so ,compared with U.pumila; its average angle between bark and branch was generally at 60 °or so, and U.pumila, at 65 °-70 °. 2. the potted elm seedlings of three kinds above were respectively proceeded to handle 7 salts level CK(0.0%), A(0.1%), B(0.2%), C(0.3%), D(0.4%), E(0.5%) and F(0.6%), arranged 6 repetition.The physiology indexs measured periodically included free proline in leaves ( pro), dissolube sugar(ds), malondialdehyde ( MDA), chlorophyll, electric conductivity, survival rate, and photo-synthesis under saltstress etc.the results showed: 1) along with the exaltation of the salt density and the prolong of time,pro ,MDA and ds inside leaves of three kinds elms all went up, the electric conductivity was reported the aggrandizement trend, the chlorophyll content and net photosynthesis were reported to descend, and the descent of survival ratio was rather obvious.The tree species were classified into two sorts of tolerance to salt stress.type 1 species Ulmus pumila was moderately resistant to salt stress (salinity between 0.1%~0.4%. type 2 species, Ulmus thomasii and U. Crassifolia were resistant to salt stress (salinity between 0.3%~0.5%) ,under 0.6% salinity circumstance there still had some of Ulmus thomasii and U. Crassifolia seedlings surviving, but Ulmus pumila in China had been dying out. 3. the potted elm seedlings of three kinds above were respectively proceeded to treat 6 water level,namely not supplied water within 6 days,12 days,18 days,24 days,30 days and 40 days, arranged 6 repetition.The physiology indexs measured periodically included Pro, dissolubility sugar, MDA, chlorophyll content, electric conductivity, survival rate, CAT activity ,soil water content and leaf water content under water stress ,and photosynthesis some time in the fields etc.the results obtained by the experiment indicated that:l) with the prolong of waterstress time, pro ,MDA ,CAT activity and ds inside leaves of three kinds elms all went up, the electric conductivity showed the aggrandized trend, the chlorophyll content, and net photosynthesis were reported to descend, and the descent of survival ratio was rather obvious .Ascension and descent ranges of different trees were different. Three tree species had stronger dry-resistance ability, but growth potential of rock elm and southern rock elm was stronger than U.pumila; the latter could grow normally under the situation of continuious 50 days' not-watering ,meanwhile the former two could still survive under the situation of continuously not-watering for 60 days. Finally, The results of subordinate function & comprehensive appraisal of the ability of three elm seedlings bearing drought and salt enunciated: rock elm ,and southern rock were all stronger than U.pumila ,but there still exsited obvious difference in its individuality.Based on this,we drew such a conclusion that the salt -and-drought tolerance of three varieties was in order of rock elm > southern rock elm > U.pumila. Therefore, rock elm and southern rock elm are all fit to be cultivated in China, especially used as the first reference to ecosystem type in the limestone mountain areas to be recovered vegetable covers.