| Upland (Gossypium hirsutum) and Sea Island cotton (G.barbadense) are two of important varieties for cotton.Among them, Sea Island cotton is of good quality, and upland cotton is better of high yielding. There's an important strategic position for cotton in Xinjiang Agricultural Production, whereas it has a serious influence on the normal growth of crops, development, quality and yield for the large area of saline land in Xinjiang.In this study, we see different cultivated species of cotton such as island cotton (Xinhai21 and Xinhai34) and upland cotton varieties (Xinluzao50 and Xinluzao57) for the test material, to culture it by the simulated condition of natural salt-stress via growth chamber of plants, then make a systematic study of the different varieties for cotton seed on the condition of salt stress, especially on the change rules of physiological and biochemical indexes for the cotton seed including the seeding emergence, biomass accumulation, parameters of photosynthetic gas exchange (Pn,Ci,Gs,Tr), activity of antioxidant enzyme (POD,SOD,CAT), and the content of osmotic adjustment substances, hope to reveal many differences on the mechanism of salt tolerance between cotton varieties of sea island and upland, provide theoretical references for the selection of salt-tolerant cotton and development of cotton cultivation on saline and alkaline soil. The main results as follows:1. Salt stress on different seedling cultivation of cotton growth and developmentIn the circumstances of 0.6% NaCl stress, the influence of salt-stress is lighter including emergence rate, plant height, fresh and dry weight, and leaf area compared with other treatment (0.8% and 1.0%), moreover both seedling of the cultivated species are in good growth, and the differences of growth status between them are not that much. Nevertheless each morphological index will decrease remarkably with the increase of salt concentration.2. Salt stress on different cotton cultivation of Seedling Photosynthesis in leavesOn the condition of low concentration for NaCl stress, the falling range of chlorophyll content in leaves is quite small in the cotton seedling of upland and island, but there's a greater influence for high salt stress on the chlorophyll content of leaves in upland cotton seedlings than in Sea Island. Salt stress could affect the normal regulations of Pn, Ci, Tr and Gs in the first true leaf from cotton seedling; in the circumstances of 0.6%-1.0% salt stress, it shows down first and then up for the cotton seedling of leaves Ci in both sea island and upland. The Ci of Xinhai 34, Xinluzao 57 and 50 started to rise in 0.8%salt stress; the Xinhai 21 began to rise in the condition of 1.0%.3. Salt stress on different cotton cultivation of seedling activity of antioxidant enzyme in leavesThe MDA content in seedling leaves of sea island and upland cotton tends to increase on condition of salt stress, and it will be increased with the increase of NaCl concentration, we found that MDA content of Xinhai 21 and Xinhai 34 are both lower than those of Xinluzao 50 and Xinluzao 57, and the increase is rather slight after being affected by salt stress. Afterwards the sea island and upland cotton seedlings being salt-treated, the activities of SOD, POD and CAT in leaves of which are all increased within a certain range, but the increase will be lessened with the increase of NaCl concentration.4. Salt stress on different cotton cultivation of seedling content of osmotic adjustment substancesUnder 0.6% salt stress, Xinhai34 and 21, Xinluzao57 and 50, the varieties of which are more sensitive and efficient in osmotic response, could be resisted from salt stress in highly effect.The Pro, SS and SP contents are all remained higher in Xinhai No.21 and 34 than in Xinluzao57 and 50.In summary, different responses of Sea Island cotton and upland cotton varieties to NaCl stress, Associated with the characteristics of their own genes. |
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