Study On Physiological Mechanisms Of Phosphorus Efficiency Of Maize

Phosphorus is one of the main limited crop yields factors of agricultural production in China and even the world. Lack of soil phosphorus has seriously hampered the crop yield and quality, although, application of inorganic phosphate fertilizers can improve the phosphorus nutrition of crops, but utilization efficiency of phosphate fertilizers is very low and phosphate is non-renewable resources, application of phosphate fertilizer is not only dependent on long-term plan. There are two main ways that increasing phosphate fertilizers use efficiency in crop: First, improve the soil for phosphorus conditions, second, improve crops use of the capacity of phosphate fertilizer. The lacks of phosphate plants have different tolerance; extensive studies show that the efficiency of phosphorus has difference between genotype.These study selected fields of soil lack of available phosphorus in the Southwest University of experimental farm, genotypic maize inbred lines are are sampled and analysised in five periods . Pre-screening of the P efficient genotypic maize inbred lines (48-2, 4419) and low-phosphorus efficient genotypic maize inbred lines (Ye107, 4065) are researched in low-phosphorus conditions, experimental results show that:1. For a period of time, chloroplast pigment content of different genotypic maize inbred lines research shows that with the time, chloroplast pigment content of different maize genotypic maize inbred lines decline under low-phosphorus treatment, with low-phosphorus; except June On the 25th the other time content of chlorophyll in the leaves was significantly lower than treatment of normal-phosphate, with the stress of extended time chloroplast pigment decline increased.2. Under normal phosphate content of MDA was slowly raising, there is little difference among these genotypic maize inbred lines, the results show that the variance of maize inbred lines have no significant difference. In low-phosphorus stress, the MDA conten in the plant leaves is higher than in normal phosphorus, with the stress of extended time, MDA has been elevated to the highest point, but there are differences within the MDA in the leaves of different species. In five times, genotypic maize inbred lines Ye107 and 4065 are very significant difference between low-phosphorus and the normal. It is show that the low-phosphorus efficient genotypic maize inbred lines are injured to the stress under the low-phosphorus, and can be used as characteristics response under low- phosphorus stress.3. Under the normal phosphorus proline content of different maize inbred lines changes inconspicuous. Under the low-phosphorus stress, proline content of different maize inbred lines is the more higher than normal phosphorus, with the stress of time preserved gradually increased; Proline content of phosphorus inefficient genotypic maize inbred lines (Ye107,4065) rise rapidly in low phosphorus.4. Under normal phosphate soluble protein content of maize genotype decline firstly, then rise and decline finally. Under low-phosphorus conditions, soluble protein content of all genotypic maize inbred lines first decline and then rise, the latter part of a small rate fluctuations, the soluble protein content of each genotypic maize inbred lines fall than in the early. Under the low-phosphorus stress soluble protein content of different maize inbred lines is the higher than normal phosphorus, low-phosphorus efficient genotypic maize inbred lines have difference significantly.5. Under normal phosphorus processing, SOD, POD, and CAT activitise of different genotypic maize inbred lines change consistent basically. Under low-phosphorus stress, SOD, POD, CAT activities of the maize inbred have increased slightly; SOD activity trend risingin in the first and then to the highest point, and then declined slightly or small fluctuations; POD activity are rise and then small decline in the latter; CAT activity increased after the first decline; it extend difference than normal phosphorus processing with the stress of time preserved gradually increased. Membrane protective enzyme activitis of different varieties maize genotype phosphorus efficiency change different direction and magnitude. SOD, POD and CAT activities of varieties maize genotype phosphorus efficiency relative stability in the trial period, and varieties maize low-phosphorus efficient genotypic maize inbred line are increased significantly in the early low-phosphorus stress. This shows that the resistance of plant relates with membrane protective enzyme activity, the absolute activity of membrane protective enzyme has nothing to do with low-phosphorus stress, but the variable trends of which related with low-phosphorus stress.6. Under low-phosphorus processing the APase activity of various maize inbred lines trend upward in five periods, the difference is that APase activities of the phosphorus efficient maize genotypic maize inbred lines are higher than the low-phosphorus efficient. Activity of genotypic maize inbred lines phosphorus efficient increased proportion large than the genotypic low-phosphorus efficient. It is the physiological adaptation features in the phosphorus stress that content of APase increases highly , is also more sensitive physiological stress indicators of plants in low-phosphorus.7. RNase activity of different genotypic maize inbred lines tends to increase in low-phosphorus stress, but increased in the different time. Under the circumstances of the normal-phosphorus and low-phosphorus, there is no relation between increasing trend of RNase activity and the phosphorus efficiency genotypic maize inbred lines, there was no significantly difference among the varieties of maize genotypes .it shows that the enzyme is not the characteristics of a low-phosphorus stress response but adversity stress.8. The relevant analysis indicated that the relevance between MDA content and SOD activity changed with time changing ,so do MDA and POD as well as MDA and CAT. Proline content and activities of POD, CAT, APase and RNase are positive correlation in each period. There was negative correlation between soluble protein content and APase activity.