外源一氧化氮对镉胁迫下长春花质膜过氧化、ATPase及矿质营养吸收的影响

重金属污染已成为全球范围的主要问题之一，其中土壤镉（Cd）污染已成为当今社会普遍关注的问题。镉是植物生长发育的非必需元素，极小浓度即可产生较大危害。一氧化氮（NO）是一种氧化还原信号分子和活性氮（RNS）, 参与植物对重金属镉胁迫的应答。长春花（Catharanthus roseus）是我国广泛栽培的兼具园林绿化和抗癌药源等有重要价值的多年生草本花卉植物。为了解镉胁迫下外源NO 对园林地被植物生理响应的调控机制，采用盆栽试验研究了外源NO（硝普钠SNP）对镉胁迫下长春花幼苗生长、 活性氧代谢、 质膜ATPase酶和5'-核苷酸酶活性以及矿质营养元素吸收的影响。结果表明， 25 mg/kg 镉胁迫严重抑制长春花幼苗的生长，显著增加地上部和根系镉的富集量，抑制对大量元素和微量元素的吸收。施加0.45、 0.90、 1.80 mg/kg 的SNP显著降低镉从根系向地上部的转运，缓解因镉胁迫对钾（K）、 钙（Ca）、 镁（Mg） 和 铁（Fe）、 铜（Cu）、 锌（Zn） 吸收产生的抑制效应，降低镉胁迫的毒害作用，促进植物生长。镉胁迫下，丙二醛（MDA）含量和活性氧（O2和H2O2）水平显著升高。施加低浓度 SNP 能够显著缓解细胞质膜过氧化，降低硫代巴比妥酸反应产物（TBARS）堆积，且对抗氧化酶和ATPase酶具有相同作用。添加0.45、 0.90、 1.80 mg/kg 的SNP 可提高镉胁迫下长春花地上部和根系的抗氧化酶［过氧化氢酶（CAT）、 超氧化物歧化酶（SOD）、 过氧化物酶（POD）］活性与抗氧化物（还原型谷胱甘肽GSH）含量，诱导质膜H+-ATPase、 Ca2+-ATPase和 5-AMPase 活性提升到正常水平（对照CK）。添加1.80 mg/kg 的SNP对镉毒害的缓解作用最有效，而添加3.60、 7.20 mg/kg 的SNP的处理则无明显效果。

Effects of exogenous NO on mineral nutrition absorption,lipid peroxidation and ATPase of plasma membrane in Catharanthus roseus tissues under cadmium stress

Heavy metal pollution has become one of the major problems in the world, and soil cadmium (Cd) pollution is the most widespread pollution. Cd is a heavy metal without biological functions and highly toxic to organism, and its accumulation in soil is becoming a severe threat to plant growth. Nitric oxide (NO) is an oxidation reduction signaling molecule and a reactive nitrogen species (RNS) with diverse physiological functions in plants. Recently, many researchers found that NO plays an important role in mediating some biotic and abiotic stress-induced oxidative stresses in plant kingdom. The valuable ornamental plant Catharanthus roseus is an important landscaping and anticancer drug source plant which is widely distributed in city gardens and on roadsides in China. Our objective was to investigate the effects of exogenous NO with the sodium nitroprusside (SNP, an exogenous NO donor) on the plant growth, reactive oxygen species (O₂ and H₂O₂), antioxidative enzymes, ATPase enzyme and mineral nutrition absorption in C. roseus seedlings under cadmium stress. A controlled pot-experiment was arranged with seven concentrations (CK, 0; Cd, 25 mg/kg Cd²⁺; T1, Cd²⁺+0.45 mg/kg SNP; T2, Cd²⁺+0.90 mg/kg SNP; T3, Cd²⁺+1.80 mg/kg SNP; T4, Cd²⁺+3.60 mg/kg SNP; T5, Cd²⁺+7.20 mg/kg SNP). Morphological, ecological, physiological indexes were observed during the growth of C. roseus. The distribution of Cd, macro (K, Ca and Mg) and micronutrients (Fe, Cu and Zn) in C. roseus plants was determined after harvest. The results show that the addition of 25 mg/kg CdCl₂ inhibits the growth of C. roseus seedlings, and dramatically increases accumulation of Cd in both shoots and roots, furthermore, the absorptions of macro and micronutrients are inhibited. Addition of 0.45 mg/kg, 0.90 mg/kg and 1.80 mg/kg SNP significantly decrease the transport of Cd from roots to shoots, alleviate the inhibition of K, Ca, Mg and Fe, Cu, Zn absorption induced by cadmium, reduce the toxicity symptoms, and promote the plant growth. The accumulation of ROS, including malondialdehyde (MDA) and superoxide radicals (O₂) generation rate, significantly is increased in C. roseus seedlings exposed to the cadmium stress, and is resulted in the lipid peroxidation, which is indicated by accumulated concentration of thiobarbituric acid-reactive substances (TBARS). Addition of 0.45 mg/kg, 0.90 mg/kg and 1.80 mg/kg SNP significantly decrease the levels of  O₂ and H₂O₂,  and lipid peroxidation. The activities of antioxidant enzymes also show the same changes. Addition of 0.45, 0.90 and 1.80 mg/kg SNP increase the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and glutathione (GSH) in C. roseus seedlings exposed to Cd. Simultaneously, addition of 0.45 mg/kg, 0.90 mg/kg and 1.80 mg/kg SNP can induce H⁺-ATPase, Ca²⁺-ATPase and 5′-AMPase enzyme activity of plasma membrane to normal levels in shoots and roots. Addition of 1.80 mg/kg exogenous SNP has the most significant alleviating effect against cadmium toxicity, while the addition of 3.60 mg/kg and 7.20 mg/kg SNP have no significant effects with cadmium treatments.