| Insufficient potassium availability has seriously limited maize production. In order to make up the lack of K and improve the planting benefit of maize, studying the difference between crop varieties about K uptake and utilization and screening maize genotype of high ability to absorb K is one of the effective ways to improve the yield of maize. In the present study, different K efficient maize varieties were collected to cultivate in hydroponic culture, then set the levels of application potassium fertilizer and not application potassium fertilizer treatment under the soil culture condition. High and low K nutrition efficient maize varieties were gained by the final biomass and combined with K efficiency and potassium sensitivity. After this, the mechanism of K high uptake and utilization efficiency in different maize varieties were studied under the conditions of nutrient solution and quartz sand. The main results were as followed:1. Results in hydroponic culture and soil potted were both proved that Yuyu 23 was the best in absorbing K and tolerancing the low-K level, it was high-K nutrition efficient maize variety. With strong tolerance to low K stress, high yield potential, and suitable for the needs of development to agricultural resources restrictive,which was the ideal type screening test. Xingnong 998, which has low K uptake efficiency and low tolerance ability under K-deficiency, was the low-K nutrition efficient maize variety. Although Xingnong 998 was weak to tolerance the K-deficiency condition, but with a high yield potential, thus was suitable to plant on the soil with high fertility and K not limiting plant growing.2.For the potassium uptake mechanism, compared with the high-K level, the height, total green leaf areas, shoot, root dry weight and ratio of root to shoot of two maize in low-K level reduced; K conversion in the root, shoot and in the whole plant decreased; root length enhanced, root surface area, diameter and radius depressed; the rhizosphere pH, 2 genotypes were different; K~+ absorption ability and K~+ affinity were increased, the tolerance ability to the K-deficiency, Yuyu 23 enhanced and Xingnong 998 reduced; root anatomic structure, the catheter number, woodiness the degree, column in radial and cortical cells in the cavity diameter all reduced. There were significant differences between the two maize varieties. When lack of K, Yuyu23 had bigger biomass, because compared with Xingnong 998, Yuyu 23 had higher root length, root surface area and root volume, smaller root diameter, stronger root activity, larger K~+ absorption ability and K~+ affinity, stronger tolerance ability to K deficiency, more proton exudation, larger cortical cells in the cavity,and the cortex ventilation organization more developed, has more cortex cell number and the cell division exuberant; these advantages more help Yuyu 23 to the absorption of nutrients.3. For the potassium utilization mechanism, during the study periods, compared with the high-K level, plant dry weight, K absorption of root, K concentration in each organ, calcium absorption, K uptake efficiency and K amount transported in the xylem under the low-K condition were significantly depressed, while the K use efficiency and K amount retranslocated from leaves to the root by phloem increased. The two maize were different leaves activated the potassium mainly through the phloem cycle to the root, and by the xylem of new leaf upward transportation, but photosynthesis product and potassium transported to the up-leaves was not synchronous. The reason why low potassium with the weight of the Yuyu 23 plants are greater than that of Xingnong 998 because in Yuyu 23 there had high K absorption rate, potassium use efficiency and more developed roots, and in the xylem a greater percentage of the potassium assigned to the upper leaf and root for its growth and better distribution mechanism. |
