芘对黑麦草根系几种低分子量有机分泌物的影响

Effects of pyrene on low molecule weight organic compounds in the root exudates of ryegrass(Lolium perenne L.)

植物根系释放分泌物与有机污染物的植物修复机制密切相关,研究具有有机污染物修复潜力植物在污染胁迫条件下的根系分泌物特征有助于揭示其修复机制。以多环芳烃修复研究中常用的黑麦草为材料(Lolium perenne L.)为材料,在营养液栽培方式下研究了在芘胁迫处理下,黑麦草根系几种低分子量有机物分泌特征。结果表明,黑麦草对芘具有较强的耐受能力,芘胁迫处理下,生物量无显著变化。黑麦草根系分泌的低分子量有机酸主要为草酸。3、6 mg/L和9 mg/L芘胁迫处理下,低分子量有机酸的组成无明显变化,但含量随芘胁迫处理浓度上升而显著增加(P<0.05);总糖分泌量随着芘胁迫处理浓度升高而呈现先略微上升后下降的趋势,相对高峰值出现在芘胁迫处理浓度3 mg/L,但差异不显著;氨基酸分泌总量随着芘胁迫处理浓度的增加而显著增多,芘胁迫浓度在3、6 mg/L和9 mg/L时,根系氨基酸的分泌总量分别是空白的1.37、2.02倍和2.65倍,但根系分泌的氨基酸组成无明显变化,19种常见氨基酸分泌的数量变化情况却不相同,分泌量总体均随着芘胁迫处理浓度的提高而增加,其中苏氨酸、丝氨酸、脯氨酸、甘氨酸、丙氨酸、亮氨酸、组氨酸和鸟氨酸的分泌量显著增多,差异显著(P<0.05)。

Polycyclic aromatic hydrocarbons（PAHs） is one kind of persistent organic pollutants in environment,some previous researches have indicated plant could facilitate the dissipation of PAHs in contaminated soil.Phytoremediation is an important measure to remove organic pollutants from contaminated soil,and the root secretion of plant is considered to be closely related to the mechanisms of phytoremediation to organic pollutants.It is in favor of revealing the mechanisms of remediation by studying the characteristics of root exudates of plant with phytoremediation potential under the stress of pollutant.In the present research,pyrene and ryegrass（Lolium perenne L.） which has been testified to be tolerant to PAHs dtress were selected as studied objects.A solution culture experiment with series of pyrene concentration was conducted to investigate the effects of pyrene on low molecule weight organic compounds in the root exudates of ryegrass（Lolium perenne L.）.The series concentration of pyrene in culture solution were designed as 0 mg/L,3 mg/L,6 mg/L and 9 mg/L.The results showed that,ryegrass had stronger tolerance to pyrene stress and grew well in culture solution spiked with 9 mg/L pyrene.Despite the biomass raised appreciably at relative low pyrene concentrations treatment（3 mg/L） and reduced at relative high pyrene concentrations treatments（3 mg/L）,no significant changes of ryegrass biomass were found in all pyrene stress treatment（P0.05）.At the pyrene spiked levels of 3 mg/L,6 mg/L and 9 mg/L pyrene stress,the organic acids,including oxlic acid,lactic acid and malic acid,were found in the root exudates of ryegrass,such component of organic acid in root exudates of ryegrass was stabilization in all pyrene stress treatment,but oxlic acid was the main composition of organic acid in root exudates of ryegrass,with a percentage greater than 97%,and its content increased significantly with the increase of pyrene spiked level（P0.05）.Compared with control treatment（0 mg/L）,oxlic acid content in root exudates of ryegrass increased from 24.6 mg/kg to 53.7 mg/kg in 9 mg/L pyrene treatment.The content of carbohydrate in root exudates of ryegrass raised appreciably at relative low pyrene spiked level（3 mg/L） and reduced at relative high pyrene spiked level（3 mg/L）,the highest carbohydrate content in root exudates took on 3 mg/L pyrene treatment,but the differences of carbohydrate content in root exudates were insignificant in all pyrene treatments（P0.05）.Total amount of amino acids secreted increased significantly with the pyrene concentration increase,which were 1.37,2.02 and 2.65 times than that of control treatment（0 mg/L） under 3 mg/L,6 mg/L and 9 mg/L pyrene treatment,respectively.Data also indicated that 19 types of familiar amino acids were found in root exudates of ryegrass and the component of amino acids in root exudates of ryegrass was stabilization under all pyrene stress treatments,but the each content of 19 types of amino acids examined was different in those root exudates under the stress of different pyrene concentration.The contents of all amino acid in those root exudates was increased with the pyrene concentration increase,especially,the contents secreted of threonine,serine,proline,glycine,alanine,histidine and ornithine increased significantly among 19 types of amino acids and the differences were significantly among different treatments with different pyrene concentration（P0.05）.