中文摘要：

以‘广林9号’桉树幼苗为试验材料,采用水培和土培试验方法研究了桉树幼苗对难溶性磷酸盐的吸收及其在低磷胁迫下的根构型和根系的生理反应,以揭示桉树高效吸收磷素的机制。结果显示：（1）桉树幼苗在含磷酸铝的缺磷培养液中吸收的磷达4.24 mg/株,与供应水溶性磷和磷酸钙处理的相当。（2）土壤缺磷或仅在上土层（0～20 cm）施磷肥处理均有利于桉树幼苗浅层根的分布,使根表面积及根数在上土层与下层（20～40 cm）比值明显增高。（3）桉树幼苗根尖的H＋-ATPase活性在缺磷处理15 d后显著提高,其根尖周围的溴甲酚紫指示剂变黄,根基环境明显酸化;根尖分泌的酸性磷酸酶活性在低磷胁迫也显著提升,且随着处理时间（10、15、20 d）的延长而进一步提高;铝和低磷胁迫能明显诱导桉树根系分泌草酸,其分泌量显著高于对照和缺磷处理。研究结果表明,桉树幼苗具有较强的难溶性磷吸收能力,而在缺磷及磷铝胁迫下根系的浅层化、根尖酸化及根分泌的酸性磷酸酶及草酸量增加可能是桉树幼苗适应酸性土壤铝毒和缺磷环境的重要机制。

英文摘要：

In order to uncover the mechanism of phosphorus（P） efficiency in utilization in Eucalyptus,we investgated the sparingly-soluble phosphates uptake and physiological response of root system and architecture to P deficiency condition at seedling stage using ‘Guanglin 9’ by hydroponics and pot-culture experiments.It was suggested that：（1）P uptake by Eucalyptus seedlings root was up to 4.24 mg/plant under low P condition of AlPO4,which was similar to those under low P condition of water-soluble P and Ca3（PO4）2.（2）Formation of shallow root was induced by P deficiency and applying P fertilizer at the topsoil （0～20 cm）,which resulted in the obvious increasing ratio of root surface and root tip number between topsoil and subsoil （20～40 cm） compared with normal P treatment.（3）15 days after low P stress,H＋-ATPase activity improved significantly in Eucalyptus seedlings and the bromocresol purple indicator turned yellow at root tip.Secreting activity of acid phosphatase from root significantly improved under P deficiency related to normal P treatment,and further improved with the extension of low P stress （10,15,20 days）.Moreover,Al toxicity and P deficiency stress can significantly induced the secretion of oxalic acid from root,and the secreting amount of oxalic acid under both Al and P deficiency conditions was significantly larger than that under the control and P deficiency conditions.These results indicated that strong uptake ability of sparingly-soluble phosphates,shallow root system induced by P deficiency and both Al toxicity and P deficiency conditions,acidification of root tip and secreting acid phosphatase and oxalic acid from root possibly contributed to the mechanism of resistance to Al toxicity and P deficiency in acid soil in Eucalyptus seedling.