| 40 maize iribred lines and 24 maize hybrids, collected from several Agricultural Universities and Institutes, were planted in pool and field, supplied with low (-P) and high (+P) phosphorus, to classify their phosphate efficiency (PE) at seedling and mature stage respectively. After classification, KH5 (a high PE genotype) and X502, Q201 (two low PE genotypes) were planted in pot and sand culture, with low (-P) and high (+P) phosphorus supply, to study the mechanism of PE discrepancy, which includes root morphology and physiology, P absorption and recycle, nitrogen and potassium absorption and distribution, light transformation and utilization, as well as excess excited energy dissipation, et al. Hybridization effects of PE and influence of P supply level on it were also analysised primarily. The results can be summarized in the follows:1. Genotypic difference in maize PE and classificationThere're significant genotypic differences in P accumulation and yield (biomass and harvestable yield) at seedling and mature stage, and the differences are affected by P supply level significantly. In field experiment, the ratio of dry matter distribute into grain among maize genotypes are almost the same, harvest index (HI) of hybrids are less affect by P supply, while HI of inbred lines have a great increase when P added. The ratio of P distributes into grain (PHI) show a significant genotypic difference, and altered variously in response to P supply, but it remains general stabilization among genotypes.Employing phosphate utilization efficiency (PUE) and relative yield (or rate of yield increase in +P) in -P regime as criteria, maizes can be classified into high phosphate efficient (PE) (more tolerant to low P) and low PE (less tolerant to low P) at seedling and mature stage in pool and field experiment respectively. The results of classification in these two stages are almost the same, suggesting that selection for maize's PE can be executed early in seedling stage. The result of classification in seedling stage shows there're only 6 inbred lines belong to high PE, and most of inbred lines (34 inbred lines) belong to low PE among 40 genotypes, reflecting the shortage of low P tolerant genotype among maize inbred lines in China.2. Hybridization effect of PE and influence of P supply on itThe increases in P accumulation, biomass and harvestable yield in maize inbred lines when P added are greater than those in hybrids generally. In seedling period, P accumulation, biomass and PUE exhibit various degree of heterosis, even some hybrids show over-high-parent heterosis, but it's affected by parent and P supply greatly. In mature stage, P accumulation, biomass, harvestable yield and PUE perform various degree of heterosis also, and low P condition is more favorable to heterosis performance. Heredity of maize PE is complicated, but hybrids with various sensitivity to P supply level still can obtain by selecting proper parents.3. Root characters and it relate to P absorption and biomass in different PE maizesLow P depressed root growth even before 4-leaf stage, and the depression increases along with the upgrowth. In high P condition, root characters of high and low PE genotype maize are close, but high PE maize possess a larger root volume and absorption area in low Pcondition, and it's helpful to uptake P from growth medium. Besides of root morphological differences, high PE maize hold a greater P absorption per volume (cm3) root system and P uptake efficiency than low PE ones significantly, regardless P supply level.For the reason of advantages in root morphology and P uptake efficiency, high PE maize has a significant greater P accumulation and net absorption than low PE maize, and lead to a significant difference in biomass, irrespective of P supply. Statistic analysis shows maize seedling's root volume is related to plant biomass significantly, and its contribution to biomass is the greatest one among the tested characteristics. In view of physiology, plant P accumulation is the final performance of i...
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