铅胁迫下杨梅根系分泌有机酸的研究

以1年生东魁杨梅Myrica rubra‘Dongkui’嫁接苗为材料,采用简单溶液收集法收集杨梅根系分泌物,用离子交换树脂从其中分离提取有机酸,用高效液相色谱测定其组成和质量分数。结果表明,在铅胁迫下能检测出酒石酸、草酸、柠檬酸和苹果酸,而对照只检测到酒石酸。杨梅根系苹果酸的分泌量随着铅浓度的升高而逐步增加,在6mmol·L^-1硝酸铅时,其根系分泌的苹果酸达到最高值（0.475±0.1360μg·g^-1）,表明铅胁迫能够持续刺激苹果酸的分泌,因而杨梅根系分泌苹果酸可能是抗重金属铅的重要机制之一;而杨梅根系酒石酸、柠檬酸和草酸的分泌量开始随硝酸铅浓度的升高而升高,在硝酸铅浓度为4mmol·L^-1时,分泌量达到最大值,随后随着硝酸铅浓度的升高,分泌量逐渐下降,特别是酒石酸的分泌量下降很快。

Organic acid exudates from Myrica rubra roots with lead stress

Organic acid exudates from one-year-old grafted Myrica rubra Dongkui roots with lead stress （0,2,4,6 mmol·L^-1） was studied using a simple solution collection method to collect root exudates,ion exchange resin to extract organic acids from root exudates,and high performance liquid chromatography （HPLC） to detect organic acid types and concentrations. Results showed that tartaric acid,oxalate,citrate,and malate were detectable with lead stress,whereas tartaric acid was only detected in the control（no lead）.Malate exudation increased as stress from Pb （NO3）2 concentration increased with a maximum from stress of 6 mmol·L^-1 Pb （NO3）2. As Pb （NO3）2 concentration increased, tartaric acid, oxalate, ann citrate from root exudation also increased reaching a maximum with 4 mmol· L^-1 Pb （NO3）2 and then gradually declining. Overall, lead continuously stimulated malate exudation from M. rubra roots. So, increased malate was probably responsible for M. rubra tolerance to lead stress.