| By means of solution culture, sand culture, soil culture and field trial, this essay studied systematically the morphological, physiological and nutritional mechanisms of different wheat genotypes with varied K use efficiencies which had been screened through field experiment and pot trail, and compared the uptake and distribution differences of nitrogen, phosphorus, calcium, magnesium, iron, manganese, copper and zinc, etc., and finally discussed the suitable screening conditions and screening indices of efficient K genotypes. The results were as follows:1. Efficient K wheat genotypes tolerated potassium stress mainly by increasing the values of Root/Shoot ratio(R/S) than by changing the other index values. The R/S had a close relationship with nutrition stress time. The R/S differences among different genotypes under the same K level were very small, and even the R/S of inefficient genotypes was higher than that of efficient K genotypes. Therefore, R/S was not the main reason of K nutrition efficiency of different genotypes. The shoot percentage for efficient K genotypes under 2 K levels especially K stress was higher than that for inefficient K genotypes, therefore, the differences of K efficiency of different genotypes mainly existed in the shoot percentage and higher shoot percentage lead to the higher K efficiency. The root weight KO/K1% of inefficient K genotypes was largely higher than that of efficient K genotypes while for R/S KO/K1% the rule was different even to the contrary. Efficient K genotypes mainly tolerated potassium stress by the relative higher R/S not by the higher root weight. Nutrition yield should be chosen under sand culture but economics index and economics yield should be chosen to study the K efficiency differences.2. Aerating and applying K treatments affected greatly the nutritional efficiency of wheat, and the effects of aerating and applying K treatments were different. Aerating increased root length and chlorophyll content but reduced plant height, root number, root weight, root volume, shoot weight and R/S. However, applying K treatment reduced R/S and chlorophyll content but increased other indices. The K nutrition efficiency might have no relations to root length and R/S, have certain relations to the volume, number and weight of roots, and have close relations with shoot weight and plant height.3. The K nutrition efficiency of wheat had not direct relations with chlorophyll content, root total absorbing area and the active absorbing area. Efficient K wheat genotypes could normally grow under K stress mainly by increasing the root specific surface area.4. There was a difference among the dynamic curves of depletion by different genotype wheats, and the depleting speeds of efficient genotype were higher while the speeds of the inefficient genotypes were low. K+ uptake kinetics parameters Km and Imax were better index for getting wheat with high K efficiency, and could be used toevaluate the differences of tolerating low K stress abilities for different genotype wheats. The classifying results, according to K+ uptake kinetics parameters Km and Imax under different K levels, were corresponding with that of different K efficiency wheat screened. However, Km and Imax of different genotype wheat behaved variedly under different K conditions, the value of which was influenced by the nutrition condition of wheat itself. Some genotypes were influenced relatively largely and the others small, while there was still a law generally. The same genotype wheat might uptake K+ with different physiological mechanism under different K levels. K+ uptake kinetics could become a kind of effective way of absorbing K+ physiology mechanism to study K efficient genotype wheat.5. There were differences in wheat K nutrition efficiency under different growing conditions. Under water culture absolute or relative higher K content and KUE were the nutritional characteristics of efficient K efficiency; Under sand culture it was relative higher K content and absolute higher KA; Un... |
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