超富集植物李氏禾根系对Cr(Ⅵ)吸收机制的研究

Mechanism of Cr(Ⅵ)Uptake by Hyperaccumulator Leersia hexandra Swartz

通过盆栽试验,研究了超富集植物李氏禾根系对C(rⅥ)的吸收特征。结果表明,解偶联剂2,4-二硝基苯酚(DNP),ATP酶抑制剂(Na3VO4)和低温(2℃)处理均显著地抑制了李氏禾根对C(rⅥ)的吸收(P<0.05)。其中,低温处理的抑制作用最明显,李氏禾根中铬的浓度较对照降低69.8%,说明李氏禾根对C(rⅥ)的吸收是需要能量的主动过程。此外,李氏禾根系对C(rⅥ)的吸收符合Michaelis-Menten方程,其米氏常数(Km)为91.08μmol·L-1。在5 mmol·L-1SO2-4处理下,该米氏常数是对照的1.27倍;而在SO2-4缺失的条件下,李氏禾根对C(rⅥ)吸收的米氏常数较对照减少了24.3%。这种拮抗关系表明李氏禾根对C(rⅥ)的吸收可能与硫酸根吸收体系有关。

Leersia hexandra Swartz, present in Southern China, has been found to be a chromium hyperaccumulator. Under hydroponic con- ditions, the mechanisms of Cr（ VI ） uptake by roots ofL. hexandra were studied at 30 txmol Cr（ VI ） .L-1. Absorption of Cr（ VI ） by the plant was significantly reduced by uncoupler 2, 4-dinitrophenol （DNP）, ATPase inhibitor（Na3VO4） and low temperature （2 ℃ ）, with the greatest inhibition（69.8% reduction） by low temperature, implying that Cr（Ⅵ） uptake by roots of L. hexandra was an active process associated with energy metabolism. In addition, Cr（ VI ） absorption followed Michaelis-Menten kinetics and was competitively inhibited by sulfate. Sulfate （SO4^2-） did not affect the maximum absorption rate ofCr（Ⅵ）（0.143~0.148 μmol·g-1 DW·h-1）, but increased the constant Km values by 27.6% compared with the control（the plants grown in 25% Hoagland solution）. However, sulfate-deficiency decreased the Km by 24.3%. This result suggested that the Cr（ WI ） uptake by the roots ofL. hexandra may be partially carried via sulfate transporters.