铝胁迫下马尾松幼苗有机酸分泌和根际pH值的变化

以马尾松幼苗为试验材料,选用砂培法研究铝胁迫对马尾松根际pH值、有机酸分泌以及植株中铝累积变化的影响。结果表明,高浓度铝导致根际pH值增加,当铝浓度高于300μmol.L-1时,根际pH值则趋于平稳。在测试的5种有机酸(草酸、苹果酸、柠檬酸、琥珀酸、乙酸)中,当铝浓度由0升至300μmol.L-1时,草酸和苹果酸根系分泌量随之升高,与根际pH值呈正相关关系;而当铝浓度高于300μmol.L-1时,草酸和苹果酸分泌量则趋于平稳,草酸和苹果酸的分泌影响根际pH值的变化。其次,活性铝通过根系进入植株后,由于营养作用和运输机制,出现分布差异,根部铝积累量明显高于茎和叶。当根系接触的铝浓度低于300μmol.L-1时,植株铝积累量与根际pH值,以及草酸、苹果酸分泌量呈显著正相关。

Changes in Rhizosphere pH and Exudation of Organic Acids of Masson Pine (Pinus massoniana) Seedlings Under Aluminum Stress

Masson pine seedlings were used as subject in a sand culture experiment to study effect of aluminum (Al) stress on rhizosphere pH, organic acid exudation and Al accumulation of masson pine seedlings. Results show that during the growth of masson pine seedlings, rhizosphere pH increased simultaneously with Al concentration rising from 0 to 300 μmol·L~(-1), but leveled off when Al concentration exceeded 300 μmol·L~(-1). Among the five organic acids (citric, oxalic, succinic, malic and acetic acids) examined in this experiment, only oxalic and malic acids demonstrated a similar trend, and a positive correlation to rhizosphere pH. The exudation of oxalic and malic acids plays an important role in variation of rhizosphere pH. Besides, once entering masson pine seedlings through their root system, active Al ions accumulated unevenly in the plant as a result of nutrition and transport mechanism and were significantly higher in roots than in stems and leaves. Al accumulation within the seedlings was positively correlated with rhizosphere pH, root exudation of oxalic and malic acids when Al concentration in the soil was under 300 μmol·L~(-1).