| In recent years, the area of land with K-deficiency expanded unceasingly; increasing K-requiring and short of K mineral resources caused a sharp contradiction between K-deficiency of soil and sustainable agriculture. In this study, hydroponics culture experiment was conducted to screening K-efficiency rice genotypes from 296 rice varieties in 2007 and 2008, and then hydroponics culture experiment with different K levels was carried out to study the characteristics of morphology and physiology of roots, chlorophyll content and resistance physiology of leaves for high K-efficiency rice type. It is important to verify the uptake, transportation, distribution and utilization of K; thus, improve K utilization and relieve the lack of K resources. At the same time, it also provides an effective way and theoretical basis for varieties improvement. The main results were as follows:1. The coefficient of variance (CV) of K accumulation (KA) and use efficiency (KUE) of these varieties were higher than those of other indices in the whole growth period, and the maximum variance was up to 40%. There were significant differences in KA, KUE and varieties, K levels and the interaction. Through cluster analysis by using KA and KUE,3691, 3693 and T33, youmi(zhu) were found to be the most K-efficient and K-inefficient genotypes of rice. Under the low K condition, plant biomass and root morphology of K-efficiency rice genotype were significantly better than that of K-inefficiency rice genotype. Plant biomass, root total length, root volume, root average diameter and root surface area of K-efficiency rice genotype were 1.60～4.60 times,1.03～1.78 times,1.14～6.29 times,1.00～2.18 times and 1.27～5.01 times higher than those of K-inefficiency rice genotype.2. Root total length, root surface area and root volume of 3693 were significantly higher than that of youmi(zhu) under each K treatment. Root total length, root surface area and root volume of the two rice genotypes increased with the K concentration increased. However, the increase of 3693 was less than youmi(zhu), which indicated that root morphology of the former was less affected on K concentration than the latter. Root length with diameter in D≤0.5 (mm) and root surface area with diameter in D≤1.5 (mm) of the two rice genotypes under each K treatment was dominant, were 64.18%～90.31% and 86.45%～94.38% of the root total length and surface area respectively. But root length and surface area in the range of D≤0.5 (mm) and D≤1.5 (mm) of 3693 were higher than that of youmi(zhu). It was visible that K-efficiency genotype 3693 had a strong ability to root, and was mainly reflected in the lateral root growth. The total absorption area, active absorption area, active absorption area ratio and root oxidation of 3693 were 1.18～1.82 times,1.32～1.92 times,0.90～1.24 times and 1.35～3.36 times higher than that of youmi(zhu), which had laid a good foundation for the absorption of K. But the root K content of 3693 was less than youmi(zhu), which indicated that the former had a regulatory function of using less K to build more biomass. At the tillering stage, root exudates of 3693 contained mainly 5 species of organic acids:oxalic acid, malonic acid, acetic acid, citric acid and succinic acid while youmi(zhu) contained 4 species besides acetic acid. At the jointing-booting stage, malonate acid was not detected in root exudates of 3693, and acetic acid was also not detected in root exudates of youmi(zhu). Oxalic acid was the predominant organic acid in root exudates both of the two, contributed more than 20% to the total acids.3. Chlorophyll content of 3693 was significantly higher than that of youmi(zhu). The chlorophyll content of the two was increased as K concentration increased; indicating that the ability of chlorophyll synthesis in the normal K concentration was strongest, but the difference between genotypes was varies considerably. In addition, SOD, POD and CAT activity of 3693 was stronger than that of youmi(zhu) under each K treatment. The antioxidant enzyme system activity of the two changed differently with the K concentration increased; but generally, the diversification amplitude of 3693 was less than that of youmi(zhu), indicating that the latter was affected by K more seriously. SOD, POD and CAT activity of the two was decreased under each K concentration with the growth stages. MDA and proline content of 3693 was less than that of youmi(zhu) under low K conditions, indicating that low K stress caused greater lipid peroxidation of the latter. MDA of youmi(zhu) was increased with the K concentration increased; however, MDA of 3693 was increased firstly then decreased with the K concentration increased. And the difference between genotypes was significant with the growth stages. |
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