Phosphorus-efficient cultivars have an increased capacity to exploit the soil and/or to convert non-available forms of phosphorus (P) into available ones for root uptake. Preliminary field observations showed that nitrogen (N) inefficient maize cultivar ZD958 exhibited high tolerance to low P soil in the shoot performance than N-efficient cultivar XY335. However, it remains unknown whether ZD958 had a higher potential in acquiring sparsely soil P than XY335. In this study, three separate glasshouse experiments were carried out to explore the capacity of both cultivars in accessing soil P. The two cultivars grew for 40 days to evaluate functional root traits in soil columns (Expt.1) and for 20 days to examine root hair length in soil filled rhizoboxes (Expt.3) in a calcareous loamy soil amended with P (high P) or background soil (low P). The third experiment (Expt.2) cultured hydroponically the both cultivars for 15 days to determine the correlation between P uptake rate and P supply intensity. Results from Expt.1 showed that shoot P content of ZD958 was significantly higher than XY335. Higher capacity of the ZD958 to access soil P were not correlated with biomass allocation and root morphological traits, since ZD958 had a lower root mass ratio at two P supplies and a lower degree of total root length and root surface area at high P than XY335. Results from Expt.3 indicated that average root hair length was not associated with the improved P uptake by ZD958, since their root hair length remained the same under low P or high P supply. Therefore, changes in root morphological traits did not explain the improved P acquisition by ZD958 roots. Rhizosphere pH, malic acid concentration and acid phosphatase activity were similar between the two cultivars, while citric acid concentration was obviously higher in ZD958 than that in XY335 (Expt.1). These results suggested that the higher capacity of P acquisition by ZD958 might be attributed to the release more citric acids from roots. P uptake rate of ZD958 was significantly higher than XY335 with the solution P ranging from 12.5 to 250 μM (Expt. 2), indicating that the changes in P uptake rate largely explained the greater P acquisition by ZD958 than XY335. Taken together, ZD958 was identified as a P-efficient cultivar, with a better adaptation to low P environment by altering the exudation of citric acid and P uptake rate. The research findings highlight the importance of plant strategies in altering the root morphological and physiological traits for a better adaptation to the low P environment, and enhance our understanding of physiological mechanisms of plant P acquisition.

磷有效品种具有增加的利用土壤能力和/或将不可用形式的磷（P）转化为可利用的根系吸收能力。初步实地观察表明，氮效率低的玉米品种ZD958的苗期表现出对低磷土壤的耐受性高于氮效率的XY335品种。但是，尚不清楚ZD958是否比XY335具有更高的获取稀疏土壤P的潜力。在这项研究中，进行了三个单独的温室实验，以探索两个品种进入土壤P的能力。两个品种生长40天以评估土壤柱的功能性状（实验1），并在20天中检查根系。在石灰质壤土中，用P（高P）或本底土壤（低P）修正的土壤填充的根瘤菌（实验3）中的头发长度。第三个实验（实验2）对两个品种进行了15天的水培培养，以确定磷的吸收速率与磷的供应强度之间的关系。实验1的结果表明，ZD958的芽P含量明显高于XY335。ZD958较高的进入土壤P的能力与生物量分配和根系形态特征无相关性，因为与XY335相比，ZD958在两个P供给下具有较低的根质量比，在高磷下具有较低的总根长和根表面积。Expt.3的结果表明，ZD958的平均根毛长度与提高的P吸收率无关，因为在低磷或高磷供应下它们的根毛长度保持不变。因此，根系形态特征的变化不能解释ZD958根系对磷的吸收改善。根际pH 两个品种的苹果酸浓度和酸性磷酸酶活性相似，而ZD958中的柠檬酸浓度明显高于XY335（实验1）。这些结果表明，ZD958更高的P吸收能力可能归因于从根部释放出更多的柠檬酸。ZD958的P吸收率显着高于XY335，溶液P的范围为12.5至250μM（实验2），表明P吸收率的变化很大程度上说明ZD958的P吸收大于XY335。综上所述，ZD958被认为是一种磷效率高的品种，通过改变柠檬酸的渗出和磷的吸收速率，可以更好地适应低磷环境。