| Maize is the third largest food crop in the world, and also the major crop for food, fodder and industrial material in China. The deficiency of P is one of the main problems that hinder the productivity of. maize. Fortunately, it could be solved through the improvement of P efficiency effectively and economically. In this study, 300 maize inbred lines of various genetic backgrounds from both domestic and abroad were screened at seedling stage with soil culture, and some inbreds were tested in full-life stage with block experiment in the field. Thus, some inbreds of low-P resistance and low-P sensitive were obtained. Meanwhile, sortie typical lines were selected to study their nutritional characters and physiological mechanism for low-P tolerance. Based on the studies, we expected to lay some theoretical foundations for the improvements of P efficiency and provide materials for such studies. The main results of this study were summarized as follows:1. Though seedling screening and full-life identifying with soil culture to gain some typical low-P tolerant and low-P sensitive maize genotypes. The methods were not only practical but also time and labor economic. The results yielded were reliable.2. P concentration for seedling screening and related indicators were proposed by multi P concentration gradient tests. The study revealed that the concentration of 0.10g/Kg is suitable for low-P treatment and 0.25 or 0.30g/Kg is proper for normal P treatment in the seedling screening in serious P deficiency soil. The synthesized index for seedling screenings was firstly presented and verified to be reliable and comprehensive. It was defined as the mean of relative P-deficiency symptom and relative dry weight. The field test showed that the reliability of this method could reach 76.9%.3. Characteristics of growth and development of certain stages were studied for different maize genotypes. It was illustrated that under low-P stress, P-tolerant lines had higher dry weight, showed no or slight P-deficiency symptom compared with that of P-sensitive lines at seedling and steming stages. The dry weights of upper leaves and stems were significantly less affected than P-sensitive lines at earing stage. At silking stage, some other indicators such as ear height, number of staminate flower branches and areas of functional leaves were observed to be significantly different among of different lines besides plant dry weight. The relative values for such indicators of P tolerant lines were much higher than that of P sensitive lines. In mature stage, yields of P-tolerant lines were higher as well. The results of this paper also showed that the P deficiency could also influence the growth stages by delaying tasselling, heading, pollen-shedding and silking stage for P sensitive line 99152S, while P tolerant lines such as 99180T and 99239T were less or non affected.4. Characteristics of P uptake, utility and distribution are found to be different for different lines in all stages. At seedling and steming stages, the efficiency of P uptake is the main contributor to low-P tolerance. And the P uptake amounts of P-tolerance lines 99180T and 99239T are significantly higher than P sensitive line 99152S under low P stress. At earing stage, the characteristics of low P tolerance are represented by the higher P accumulated amount in upper leaves. When come to the silk stage, P uptake and redistribution efficiencies of 99180T and 99239T are still significantly...
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