几种多环芳烃的植物吸收作用及其对根系分泌物的影响

采用水培试验方法,以多年生黑麦草(Lolium multiflorum Lam.)为供试植物,研究了芘、菲、苊和萘的植物吸收作用及其对根系分泌物的影响.结果表明,黑麦草能明显吸收富集多环芳烃(PAHs);随培养液中PAHs浓度的升高,其在黑麦草根和茎叶中的含量增大,且根的PAHs含量、富集系数要远大于茎叶.芘、菲、苊、萘污染胁迫下,黑麦草根系分泌物中可溶性有机碳、草酸和可溶性总糖的含量均高于无污染对照.供试污染浓度范围内,随着培养液中菲、苊、萘浓度提高,可溶性有机碳、草酸及可溶性总糖的分泌量增大;但在芘胁迫下,与污染对照相比,分泌量的增加幅度随着芘浓度的升高则呈先增大后减小的趋势.在较低污染强度下,供试PAHs对根系分泌物的促分泌效应由强到弱依次为芘、菲、苊和萘.4种PAHs对可溶性糖类的促分泌作用最强,其分泌量的增加幅度明显大于可溶性有机碳和草酸.

Plant uptake of polycyclic aromatic hydrocarbons(PAHs) and their impacts on root exudates

A hydroponic experiment was conducted to investigate the uptake of the representative polycyclic aromatic hydrocarbons (PAHs) pyrene, phenanthrene, acenaphthene, and naphthalene, by ryegrass (Lolium multiflorum Lam.) and their impacts on root exudates. The PAHs were obviously absorbed by ryegrass, and concentrations of tested four PAHs in plant root or shoot increased as their concentrations in solution increased. Root concentrations and root concentration factors (RCFs) of PAHs were much larger than those of shoots. Compared with the control treatments with no PAHs in solution, PAH contamination promoted the root exudation of soluble organic carbon, oxalic acid, and soluble carbohydrate, and the amounts of these root exudates increased with the concentrations of phenanthrene, acenaphthene, and naphthalene in solution. In contrast, with the increment of pyrene concentrations in solution, the amounts of these root exudates increased first and decreased thereafter. The promotion of root exudation of ryegrass by PAH contamination was in the order pyrene>phenanthrene>acenaphthene>naphthalene. More significant promotion by PAHs was observed for soluble carbohydrate than other root exudates including soluble organic carbon and oxalic acid.