Study On Screening For N And K Efficiency Rice Genotype And Its Physiological Mechanisms

In this study,screening N and K efficiency rice genotypes from 18 rice varities through hydroponics culture experiment twice. Root morphological characteristics and physiological characteristics were studied through hydroponics method and NR activity, antioxidant enzyme, resistance physiological mechanism, photosynthetic physiological mechanism and their correlation with yield were studied at tillering stage,jointing stage, booting stage, full panicle stage, maturing stage through soil culture method in different N efficient rice, in order to verify that the relationship between yield and morphological, resistance physiological, photosynthetic physiological indexes, and the suitable period and indirect indexes to screen double N and K efficiency rice varities, which can provide theoretical significance for the high-efficient and high-yield cultivation.The main results of this study were as follows:1.18 different rice varieties were classified for low K stress(5mg/L) in hydroponic culture at seedling stage by adopting relatively low potassium tolerance index and variance and principal component analysis method.Result showed significant to very significant differences in 16 potassium efficiency related traits among 18 rice genotypes. Principal component analysis showed that theaccumulation contribution rate for first five principal components had reached 90.972%,which implied that they contained most of the information to reflect the all trait resource. The proportions of relative plant dry weight, shoot dry weight,root dry weight,root/shoot ratio, shoot potassium uptakeand plant potassium uptake in the five principal components were higher, so they can used as screening index of rice potassium efficiency germplasm resources screening at seedling stage.The comprehensive evaluation results showed that the highest score(2.2753) was “Zhanyou 2009”and the second was “Teyou 524”(2.2545), both were the best potassium tolerance rice varieties; Huangfengzhan, Huanghuazhan, Boyouwan3,Ⅱyou3550 et. were medium potassium tolerance varieties; the least score(-1.8583) was “Boyou043”, which was low potassium sensitive varieties.2. 8 K efficiency rice varieties were classified for low N stress(5mg/L) in hydroponic culture at seedling stage by adopting relatively low potassium tolerance index and variance and principal component analysis method. Result showed that very significant differences in 15 nitrogen efficiency related traits between two nitrogen treatment and among cultivars. Principal component analysis showed that 4 principal components were extracted according to the principle that characteristic value was more than 1, the first 4 principal components had an accumulative contribution rate of 91.287%, implying that they contained most of the information to reflect the overall trait resources.A comprehensive evaluation showed that Qi Huazhan had the highest score(1.6624) and the following was Huang Huazhan(1.5192) for nitrogen efficiency rice cultivars in the 8 tolerant low K rice cultivars; Te you524 had the medium score(0.4232) for nitrogen medium efficiency rice cultivars; Zhanyou2009 and Ⅱyou3550 respectively score-1.4041and-1.3087, which were nitrogen inefficiency rice cultivars.Different nitrogen efficiency type rice cultivars had significant difference in rice root physiology characterisitics, the indexs of relative root total absorbing surface area, relative root active absorbing surface area, relative total/active absorbing surface area in nitrogen efficiency rice cultivars were all higher than those in nitrogen inefficiency; however, relative total absorbing surface area/volumn had no obvious regularity. It was feasible to screen efficience rice cultivars of nitrogen and potassium, we can conformate preliminaryly that the nitrogen and potassium efficiency in rice was not controlled by the same gene and still need to verified this conclusion by using biology techniques.3.Studied the root morphological and physiological characteristics on double N and K efficiency rice(Qi Huazhan, Huang Huazhan) and K efficiency but N inefficiency rice(Zhanyou2009, Ⅱ you3550) by hydroponic experiment.Result showed that the differences of root morphological and physiological characteristics indexes were reached significant level among different N efficiency type,root dry weight, root volume, total absorption area,active absorption area and active absorption area ratio, amount of alpha NA oxidation of two kinds of N efficiency rice at low N stress were all lower than normal for N level, while the root-shoot ratio, specific surface area were the opposite trend.Relative root dry weight,root volume, relative total absorption area and active absorption area, relative active absorption area ratio and relative specific surface area of N efficiency rice were all higher than N inefficiency type, but the root morphology and physiological indexes were not all higher than N inefficient type, which showed that N efficiency rice type had higher relatively resistance on barren, but not necessarily efficient absorption type.4.Studied resistance physiological mechanism and photosynthetic physiological mechanism on double N and K efficiency rice(Qi Huazhan, Huang Huazhan) and K efficiency but N inefficiency rice(Zhanyou2009, Ⅱyou3550) by soil experiment. Result showed that the NR activity, POD, CAT activity and proline content, soluble sugar content, soluble protein content were decreased at low N and K stress, but the stress effect on N efficiency type rice was lower than that of N inefficient type; the content of MDA increased at low N and K stress and with the increase of stress level and strengthening, but the damage level of N efficiency type was lower than N inefficiency type. Correlation analysis showed that MDA content was negatively related with yield, and CAT activity was positively related with yield at different treatment in all growth stage the relationship between yield and other indicators were not all the same in different growth period.So CAT activity and MDA content can be as the indexes to screen N efficiency type of rice.Low N and K stress reduced photosynthetic rate(Pn), stomatal conductance(Gs), transpiration rate(Tr) and chlorophyll content and increased CO2 concentration of intercellular(Ci), but Pn, Ci, Tr, chlorophyll content were strongly influenced by low N stress and the Gs was greatly influence by the low K stress. The correlation analysis showed that the correlation rule between each photosynthesis index and yield was not consistent, but in the tillering stage, full panicle stage, mature stage is better and Pn, Gs,Tr,chlorophyll content were all positively correlated with yield, but Ci was negatively correlated with yield.Therefore, the photosynthesis indicators of tillering stage, full panicle stage, mature stage can be used to screen N efficiency of rice.