| The shortage of potassium(K) resources is a problem that our country and the world need to solve. So studying the synergistic and substitution effects of sodium(Na) and K is an effective way to improve the efficiency of crop potassium. This research was conducted to study the interaction and substitution effects of Na and K on growth, nutrient uptake and utilization of different K-efficiency cotton genotypes(HG103 and LG122), and explore the difference between the two cotton genotypes. On the basis of the study, HG103 was selected to explore the effects of partial replacement of K by Na on seedling growth, photosynthetic performance, sugar metabolism, osmotic regulation and so on. In order to further elucidate the physiological mechanism of substitution effects of Na and K in cotton, aiming to provide a scientific reference, so as to provide theoretical basis for scientific use of potash in practical production. The main results were as followed:1. The root length, the dry matter weight of the shoot and whole plant of HG103 and LG122 were enhanced with addition of Na(K) in deficient or adequate K(Na). While the effect of Na and K interaction on root length, relative growth rate of stem length was significant.2. The K content of each part was reduced, but the Na content and accumulation of both genotypes were increased with addition of Na. While with addition of Na in deficient K, the whole plant K use efficiency of HG103 was significantly improved by 32%. And with addition of Na in adequate K, the K use efficiency was increased by 113% and 77% respectively. Meanwhile, the K content, K accumulation and Na use efficiency of both genotypes were significantly enhanced with addition of K, but the Na content was decreased. Na and K interaction also has a significant impact on Na use efficiency.3. Na application promote the synthesis of carbohydrate, protein and esters in leaves of HG103 and LG122 in deficient K, however Na has inhibitory effect in adequate K. Meanwhile, In deficient or adequate K, Na improves the number of stomata, but in deficient or adequate Na, K reduced the esters and protein content, the number of stomata, make epidermal cells more full.4. During cotton seedlings, Na can partly replace K. The whole plant dry matter weight of HG103 of 2/3K+1/3Na treatment is almost the same with the total K treatment, thus it indicates 1/3K can be replaced by Na. Meanwhile, The dry matter weights, K, Ca, Mg accumulation of each parts except root and stalk of 2/3K+1/3Na treatment is higher than 1/3K+2/3Na. So the effects of partial replacement of K by Na of 2/3K+1/3Na treatment is better than 1/3K+2/3Na.5. Compared with treatment K, the K use efficiency of 2/3K+1/3Na treatment of HG103 increased by 41%, is higher than that of LG122 by 24%. Meanwhile, the K use efficiency of 1/3K+2/3Na of HG103 enhanced by 118%, is also more than LG122. So HG103 is better than LG122.6. Under the addition of Na in 2/6K and 1/6K treatment, the leaf area of HG103 increased by 5% and 10%, net photosynthetic rate improved by 18% and 160%, the shoot dry matter weight enhanced by 12% and 7%. Therefore, in deficient K, supplement Na could improve leaf area, net photosynthetic rate, leaf starch content and promote the absorption of K and Na, so increasing the absorption of nutrients and dry matter accumulation, ultimately promote the growth of HG103.7. The effects of different proportions replacement of K by Na on leaf chlorophyll, soluble sugar and sucrose content of HG103 are different. The chlorophyll content of the low proportion replacement reduced, but soluble sugar and sucrose content increased. However, high proportion replacement in contrast. |
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