镉胁迫下稀土镧对蚕豆幼苗根尖细胞分裂和吲哚乙酸氧化酶的影响

重金属胁迫下稀土调节植物细胞分裂与增殖的生理机制至今尚不完全清楚。为此,将蚕豆幼苗分别培养于营养液、6μmol.L-1氯化镉(CdCl2)以及6μmol.L-1CdCl2与2~480μmol.L-1硝酸镧La(NO3)3]的复合溶液,14 d后检测与根尖细胞分裂和生长相关的部分生理指标。结果表明,添加2~120μmol.L-1外源La减少了根部组织对Cd的吸收,超过此剂量范围则促进了Cd的积累。同时,K、Zn、Fe等矿质元素含量,以及吲哚乙酸氧化酶同功酶及其活性呈现"U"型剂量效应的变化,而根尖细胞分裂指数和根长则呈现类似倒"U"型的剂量效应变化趋势。因此,矿质元素和吲哚乙酸氧化酶活性的失衡和干扰是La调节Cd胁迫下蚕豆幼苗根尖细胞分裂与生长的重要生理机制。

Effects of Rare Earth Lanthanum on Root Tip Cell Mitosis and Indole Acetic Acid Oxidases in Roots of Vicia faba L.Seedlings Under Cadmium Stress

Physiological mechanisms of rare earth element(s) on regulating plant cell mitosis and growth under heavy metal stress are not completely understood.In the present work,Vicia faba L.seedlings were hydroponically cultured for 14 days in nutrient solution,containing single treatment of 6 μmol·L-1 CdCl2,and combination of 6 μmol·L-1 CdCl2 and 2~480 μmol·L-1 of La,respectively.Some physiological parameters concerning cell mitosis and growth were then determined.The results showed that the addition of 2~120 μmol·L-1 of extraneous La contributed to decline of contents of Cd in the roots compared with the single Cd treatment,followed by Cd enhancement with the increase of La.The increase of La also led to nearly"U"-shaped enrichment of K,Zn,Fe or other mineral elements,and"U"-shaped alteration of indole acetic acid(IAA) oxidase isozymes and activities in the roots.However,root tip cell mitosis and root lengths changed like an inverted "U"-shaped dose response curve.In brief,the regulation mechanisms of La on the cell mitosis and growth of V.faba seedlings are attributed to unbalance and disturbance of some mineral elements and IAA oxidase under Cd oxidative stress.