不同磷水平下植物体内镉的积累、化学形态及生理特性(英文)

ACCUMULATION, CHEMICAL FORMS AND PHYSIOLOGICAL CHARACTERIZATION OF CADMIUM IN PLANTS AFFECTED BY PHOSPHORUS *

在控制条件下 ,将玉米、小麦植株在含有不同浓度磷 (c(P) 0 ,0 .12 ,0 .6 ,3.0mmol/L)和镉 (c(Cd) 0 ,4.0 μmol/L)的营养液中培养 2 1d ,研究植株体内各种镉的形态、生理特性和酶活性的变化 .选择三种主要镉的形态 ,即氯化钠可提取态 (镉与蛋白质或多肽结合态 ) ,醋酸可提取态 (镉与磷酸盐的结合态 )和去离子水可提取态 (水溶性、有机酸盐镉的形态 )作为优势态镉加以分析和研究 .结果表明 ,提高介质中磷的浓度 ,降低了与蛋白质结合态镉的含量 ,而增加了镉 -磷酸盐的含量 .与缺磷或低磷供应比较 ,在c(P) 0 .6～ 3.0mmol/L下的两种作物根系脱氢酶的活性明显提高 ,根系K+的透性减小 ,玉米叶绿素的含量明显升高 ,硝酸还原酶活性增大 .但高磷 (c(P) 3 .0mmol/L)处理的植株 ,各项生理指标不如 0 .6mmol/L磷处理组植株好 ,表明在磷 -镉的拮抗中 ,外施磷浓度并非越高越好 .相反 ,过量的磷会抑制植物的生长与干物质的积累 .小麦植株对镉的耐性大于玉米 .图 5表 4参

Corn and wheat cultivated in hydroponic culture solution with supplies of cadmium ( c (Cd)0, 4.0 μ mol/L) and phosphorus ( c (P)0, 0.12, 0.6, 3.0 mmol/L) under controlled growth conditions in relation to the chemical forms of Cd, growth and physiological parameters, and enzyme activities of 21-day-old plants were investigated. The three predominant forms of Cd were NaCl-extractable Cd (related to Cd-binding proteins or polypeptides), acetic acid-extractable Cd (CdHPO 4, Cd 3(PO 4) 2, or Cd-polyphosphates), and water-extractable Cd (organic acid complexes). Increasing application of P tended to reduce the percentage of Cd combined with proteins and increase the amount of Cd-phosphates. Decreased cell plasma membrane permeability and K + leakage of Cd-treated plants were observed with the P supply of 0.6 mmol/L. The moderate supply of P (0.6 mmol/L) also improved the contents of chlorophyll pigments, the activities of root dehydrogenase and leaf nitrate reductase in Cd-treated plants, whereas supply with an excess of P (3.0 mmol/L) showed not to be more effective in the alleviation of Cd toxic to plants. Results showed that wheat was more tolerant to Cd toxicity than corn. Fig 5, Tab 4, Ref17