耐铝的和对铝敏感的玉米自交系根系的有机酸分泌

Organic Acid Secretion from Roots in the Al-Tolerant and Al-Sensitive Maize Inbred Lines

对玉米不同耐铝自交系在含Al3 + (0 .1mmol/L)的完全营养液和AlCl3 14.3μmol/L +CaCl2 2 2 7.5μmol/L溶液等两种溶液中根系有机酸的分泌特征进行了研究。铝胁迫下 ,耐铝自交系Z1的生长与正常偏离不大 ,表现出较强的耐铝性 ,而铝敏感自交系Z2的生长则受到明显抑制。 2种自交系根系分泌的有机酸种类包括苹果酸、柠檬酸、琥珀酸、马来酸、乙酸和草酸等 ,以苹果酸为主 ;其分泌量随铝处理时间而异。在两种溶液中 ,铝胁迫均可显著增加Z1苹果酸分泌量 ,且根系内苹果酸含量也显著增加。铝胁迫下 ,Z1根系NADP 苹果酸脱氢酶活性显著增加。从对试验结果分析得出 :根系分泌苹果酸可能是玉米耐铝自交系适应酸性土壤逆境的生理特性之一 ,而分泌的苹果酸可能是在根系中通过PEP→OAA→苹果酸途径合成的。

In this study, the character of root organic acid secretion in the 14.3 μmol/L Al 3+(in 227.5 μmol/L CaCl 2 solution) and in the 0.1 mmol/L Al 3+ (in nutrient solution) in two maize (Zea mays L.) genotypes , inbred line Z1 (Al-tolerant) and Z2 (Al-sensitive) was examined. The effects of 0.1 mmol/L Al 3+ stress on the root organic acid secretion and content in different period (after 1, 3, 7, 15, 20 days treatment) in Z1 and Z2 were comparatively studied, and relationships between malate dehydrogenase activity and root organic acid content or secretion were also examined. The results showed that the sensitivity of two inbred lines to Al was different. Z1 was found to be more tolerant to Al than that of Z2. After 3 days treatment, Z1 significantly exceeded Z2 in the relative biomass of roots and plant (Fig.1). Organic acid content and secretion from the entire root system were investigated via HPLC. The analysis showed that kinds of secreted organic acids, such as oxalic,malic,acetic,maleic,citric, succinic ect, were various in different periods, in which malic acid always remained(Table 1). The secreted malic acid of Z1 could be increased remarkably by Al stress, however Z2 kept low in different period in CaCl 2 solution (Fig.2A) and in nutrient solution (Fig.3). The root organic acids included malic,succinic,acetic, maleic ect, in which succinic acid was the highest in content. Aluminum stress increased root malic acid concentrations in Z1 and total root organic acid concentrations in both inbred lines (Fig.4). In the roots, NADP-malate dehydrogenases activity was increased significantly by Al stress in Z1, but decreased in Z2. NAD-malate dehydrogenase activity had a tendency of reducing in the both inbred lines. In the leaves, both enzyme activities were reduced by Al stress (Fig.5). The results suggested that the secreted malic acid was probably synthesized by the second way (PEP→OAA→Malate) in the roots.