缺磷白羽扇豆排根与非排根区根尖分泌有机酸的比较

采用根系分泌有机酸原位收集方法及高效液相色谱技术分析了供磷及缺磷后不同时间白羽扇豆(LupinusalbusL .)非排根区根尖和排根分泌有机酸的种类和数量 ,以及相应的根尖、排根组织 ,茎木质部、韧皮部汁液中有机酸含量的变化。结果表明 :(1)缺磷能够诱导白羽扇豆根系产生大量排根 ,根系的有机酸分泌量也明显增加。 (2 )无论在供磷或缺磷条件下 ,排根与非排根区根尖组织中的有机酸种类相同 ,但排根主要分泌柠檬酸和苹果酸 ,而非排根区根尖主要分泌苹果酸和乙酸。 (3)缺磷后非排根区根尖分泌苹果酸的量增加 ,至第 17天达到高峰 ;排根开始分泌柠檬酸的时间相对较晚。缺磷后排根分泌柠檬酸的量随缺磷时间的延长不断增加。 (4 )在缺磷的排根与非排根区根尖组织和茎木质部伤流液中含有大量柠檬酸和苹果酸 ,但在茎韧皮部汁液中则几乎检测不到这两种有机酸。上述结果表明 ,尽管排根和非排根区根尖组织中的有机酸种类相同 ,但它们向外分泌的有机酸种类不同。缺磷后排根及非排根区根尖增加向外分泌的有机酸主要在根中合成

Comparative Studies on Organic Acid Exudation by Tips of Proteoid and Non proteoid Roots of Phosphorus deficient White Lupin

The present study was based on a non destructive method for collecting root exudates. Organic acids exuded from tips of non proteoid and proteoid roots of white lupin ( Lupinus albus L.) grown in nutrient solution with or without P supply were analyzed qualitatively and quantitatively by HPLC. Organic acids in root tissues, phloem sap and xylem exudate were also extracted and analyzed. The results showed: 1. More proteoid roots were induced by P deficiency stress in white lupin. 2. The same organic acids were found in tissues of both proteoid and non proteoid roots (Figs.8, 9). Malic acid and acetic acid were the major organic acids excreted from the tips of non proteoid roots (Fig.4), while citrate and malic acid were the major ones from proteoid roots (Fig.6). Secretion of the organic acids by both tissues was enhanced by P deficiency. 3. Secretion of malic acid from the tips of non proteoid roots increased after the P deficiency, and reached the highest level on the 17th day (Fig. 5), while secretion of citric acid from the proteoid roots began later, and increased steadily with the prolongation of the P deficient period (Fig.7). 4. Large mounts of malic and citrate acid were found in tissues of P deficient proteoid and non proteoid roots, as well as in xylem, while in phloem saps almost no citrate and malic acids were detected, even under the P deficiency stress (Figs.10, 11). The results showed that, though the organic acids in tissues of proteoid roots and tips of non proteoid roots were the same, the organic acids exuded by the two root tissues were different. The increased amount of malic and citrate acids in root tissues as well as that exuded from roots to outside under the P deficiency stress were synthesized in roots themselves.