玉米幼苗根系对Cr(Ⅲ)的吸收动力学特征及途径探讨

Kinetic characteristics and pathways of Cr(Ⅲ)uptake by maize seedling roots

为探讨玉米幼苗对Cr(Ⅲ)的吸收途径,通过水培试验方法,研究了不同Cr(Ⅲ)处理浓度(0~20 mg·L^(-1))对玉米幼苗Cr(Ⅲ)的吸收动力学特征的影响,以及ATP酶抑制剂、离子通道抑制剂、Fe(Ⅲ)对玉米幼苗根系Cr(Ⅲ)吸收的影响。结果表明:玉米幼苗根系吸收Cr(Ⅲ)的最大吸收速率(V_(max))为121.4 mg∙kg^(-1)∙d^(-1),显著高于地上部的16.3 mg·kg^(-1)·d^(-1)(P<0.05);根系吸收Cr(Ⅲ)的离子载体与离子的亲和力(K_(m))为12.2 mg·L^(-1),显著低于地上部分的180.8 mg·L^(-1)(P<0.05)。ATP酶抑制剂Na_(3)VO_(4)显著抑制了玉米幼苗根系对Cr(Ⅲ)的吸收(P<0.05)。Ca^(2+)通道抑制剂LaCl_(3)和K^(+)通道抑制剂C_(8)H_(2)0CIN均不抑制玉米幼苗根系对Cr(Ⅲ)的吸收(P>0.05)。与正常营养液相比,缺Fe(Ⅲ)处理下的玉米幼苗根系吸收Cr(Ⅲ)的V_(max)增加了20.0%,K_(m)数值仅减少了5.0%,但Fe(Ⅲ)处理下的玉米幼苗根系吸收Cr(Ⅲ)的V_(max)减少了46.0%,K_(m)数值减少了56.0%。研究表明,玉米幼苗吸收的Cr(Ⅲ)主要富集在玉米幼苗的根部,只有很少被转移到地上部分;玉米幼苗根系对Cr(Ⅲ)的吸收存在主动吸收的过程,进入细胞膜的途径与Ca^(2+)和K^(+)通道无关,Fe(Ⅲ)抑制了玉米幼苗根系对Cr(Ⅲ)的吸收。

The aim of this study is to explore the absorption pathway of Cr(Ⅲ)in maize seedlings.The effects of different Cr(Ⅲ)treatment concentrations(0–20 mg·L^(-1))on the Cr(Ⅲ)absorption kinetics of maize seedlings and the effects of an ATPase inhibitor,an ion channel inhibitor,and Fe(Ⅲ)on the absorption of Cr(Ⅲ)in maize seedling roots were determined using hydroponics culture.The results indicated that the maximum absorption rate(V_(max))of Cr(Ⅲ)by maize seedling roots was 121.4 mg·kg^(-1)·d^(-1),which was significantly higher than the V_(max)of the aboveground parts of the seedlings(16.3 mg·kg^(-1)·d^(-1),P<0.05).The affinity between the ion and ionic carrier(K_(m))of Cr(Ⅲ)absorbed by the roots was 12.2 mg·L^(-1),which was significantly lower than the K_(m)of the shoots(180.8 mg·L^(-1),P<0.05).The ATPase inhibitor,Na_(3)VO_(4),significantly inhibited the uptake of Cr(Ⅲ)by maize seedling roots(P<0.05).Neither the Ca^(2+)channel inhibitor,LaCl_(3),nor the K^(+)channel inhibitor,C_(8)H_(2)0CIN,inhibited the uptake of Cr(Ⅲ)by maize seedling roots(P>0.05).Compared with the uptake of a normal nutrient solution,the V_(max)of Cr(Ⅲ)uptake by maize seedling roots with Fe(Ⅲ)deficiency increased by 20.0%,but the K_(m)only decreased by 5.0%.However,under Fe(Ⅲ)treatment,the V_(max)of Cr(Ⅲ)uptake decreased by 46.0%and the K_(m)decreased by 56.0%.These results indicate that Cr(Ⅲ)mainly accumulated in maize seedling roots,and the transfer ability to the aboveground parts of the seedlings is relatively poor.The absorption of Cr(Ⅲ)by roots occurres via an active absorption process and is inhabited by Fe(Ⅲ).Cr(Ⅲ)uptake is not related to Ca^(2+)or K^(+)channels.