在综合了大量国内外磷营养效率研究结果的基础上，从多方面分析了磷吸收效率差异的可能生理机制，并进行了简要的评论，对今后的研究重点提出了建议。

本文在综合了国内外磷营养效率研究结果的基础上，从利用效率方面分析了磷营养效率差异的可能生理机制并进行了简要的评论，对今后的研究重点提出了建议。

本试验采用溶液培养和砂基培养的方法，研究了NO3-N和NH4+-N两种不同形态氮素对燕麦营养生长、氮代谢、根际pH 及磷素利用的影响。结果表明，在NO3-N和NH4+-N同时存在的条件下，燕麦生长明显优于单一NH4+-N 或NO3-N处理，且植株生长量特别是根系生长量随着NO3-N在氮源中比例的提高而增加。燕麦吸收NO3-N和NH4+-N对根际pH产生不同影响，吸收NO3-N，根际pH逐渐升高，而吸收NH4+-N使根际pH有所降低。当水溶性磷充足供应时，氮素形态对燕麦生长和磷素吸收利用的影响是一致的，但当供应溶解性低的磷素时，氮素形态对二者的影响是不一致的，生长量与磷素吸收利用率间没有显著的相关关系，而且根际pH与磷素吸收利用率间也没有显著的相关关系。

试验采用溶液培养的方法，研究了NO3-N和NH4+-N两种不同形态氮素对燕麦营养生长、氮代谢及根际pH的影响。结果表明：在NO3-N和NH4+-N两种形态氮素同时存在的营养介质中，燕麦生长明显优于单一供应NH4+-N或NO3-N处理，且植株生长量特别是根系生长量随着NO3-N在氮源中比例的提高而增加；燕麦吸收NO3-N和NH4+-N会对根际pH产生不同影响，吸收NO3-N时，根际pH逐渐升高，而吸收NH4+-N却使根际pH有所降低。

Low phosphorus availability induces the formation of cortical aerenchyma in roots. The adaptive significance of this response is unknown. We hypothesized that aerenchyma may be helpful to low-phosphorus plants by reducing root respiratory and phosphorus requirements, thereby increasing the metabolic efficiency of soil exploration. To test this hypothesis we investigated aerenchyma formation, root respiration and tissue phosphorus concentration in maize and common bean genotypes in response to phosphorus availability and ethylene treatments. Genotypes differed substantially in their ability to form aerenchyma in response to low phosphorus. Aerenchyma formation was disproportionately correlated with reduced root respiration: roots with 30% cross sectional area as aerenchyma had 70% less respiration than roots without aerenchyma. Aerenchyma formation was also proportionally correlated with reduced root phosphorus concentration. Variation in aerenchyma formation was correlated with root respiration and phosphorus concentration, regardless of whether such variation was caused genetically or by ethylene or phosphorus treatments. Results with isolated roots were confirmed by measurement of whole root respiration of intact maize plants. Our results support the hypothesis that aerenchyma formation reduces the respiratory and phosphorus requirements of soil exploration by roots, and thus, represents a useful adaptation to low phosphorus availability.