Abstract: To explore the response of root exudates to phosphorus (P) deficiency in stylo (Stylosanthes guianensis), in this study, the effects of normal P supply (+P) and P deficiency (-P) on the growth and root exudates of stylo variety Reyan No.5 were analyzed with hydroponic experiments. The results showed that P deficiency stress significantly decreased plant dry weight and toal P content of stylo. Subsequently, a total of 101 root secretory metabolites had been detectd out in the root metabolome. These metabolites belonged to seven categories, such as organic acids, amino acids, flavonoids, saccarides and alcohols. Among them, there were 25 differential accumulation metabolites between -P and +P treatments. The secretions of three organic acids:caffeic acid, 1-aminocyclopropane-1-carboxylic acid, and α-ketoglutaric acid were significantly increased under -P treatment;and among them, α-ketoglutaric acid was able to efficiently solubilize aluminum phosphate. By fluorescence quantitative PCR technique, it was revealed that the expression of SgICDH, a citrate dehydrogenase gene involved in α-ketoglutarate synthesis in stylo roots, was significantly increased under -P treatment. In summary, stylo roots promote the synthesis and secretion of α-ketoglutarate through up-regulation of SgICDH gene expression, thereby enhancing the utilization of insoluble P to adapt to low -P stress.

Key words: Stylosanthes guianensis, Phosphorus deficiency, Root exudates, Metabonomics, Organic acids

摘要： 为探索柱花草（Stylosanthes guianensis）根系分泌物对缺磷胁迫的响应，本研究以‘热研5号’柱花草为材料，通过水培试验，分析了正常供磷（+P）和缺磷（-P）处理对柱花草生长及根系分泌物的影响。结果表明，相对于+P处理，-P处理显著降低了柱花草植株干重和全磷含量。随后，代谢组共检测到101个根系分泌代谢物，可被分为有机酸、氨基酸、类黄酮、糖及醇类等七类，其中-P与+P处理间的差异累积代谢物25个。属于有机酸的咖啡酸、1-氨基环丙烷-1-羧酸和α-酮戊二酸在-P处理下的分泌量显著增加，且其中α-酮戊二酸对磷酸铝具有较强的溶解能力。此外，荧光定量PCR分析发现，柱花草根系中参与α-酮戊二酸合成的柠檬酸脱氢酶基因SgICDH在-P处理下的表达量显著增加。因此，柱花草根系通过上调SgICDH基因的表达，促进α-酮戊二酸的合成与分泌，从而增强对难溶性磷的活化利用，以适应缺磷胁迫。

关键词: 柱花草, 缺磷胁迫, 根系分泌物, 代谢组学, 有机酸