di Toppi Luigi Sanità, Marabottini Rosita, Vattuone Zulema, Musetti Rita, Favali Maria Augusta, Sorgonà Agostino, Badiani Maurizio
Dipartimento di Biologia Evolutiva e Funzionale, Sezione di Biologia Vegetale, Università di Parma, viale delle Scienze 11/A, I-43100 Parma, Italy.
Dipartimento di Agrobiologia e Agrochimica, Università della Tuscia, via SC De Lellis, I-01100 Viterbo, Italy.
Funct Plant Biol. 2005 Aug;32(7):611-618. doi: 10.1071/FP04237.
Total and cell wall-bound cadmium and the major antioxidants were measured in thalli of the lichen Xanthoria parietina (L.) Th. Fr. exposed to two Cd concentrations, namely 4.5 or 9.0 μm, in liquid medium during exposure periods of either 24 or 48 h. Total Cd in the thalli was within the range of previous field measurements and was proportional to the exposure concentration, but less than proportional with respect to exposure duration. More than half of the total Cd was immobilised by the cell wall. The adopted conditions of Cd stress caused: (i) no changes in dry weight and protein concentration; (ii) an increase in the level of ascorbic acid and a decrease in that of reduced glutathione, as well as an increase in guaiacol peroxidase activity; (iii) no changes or moderate decreases in the activities of superoxide dismutase, catalase, dehydroascorbate-, NADPH-dependent glutathione disulfide-, and monodehydroascorbate reductases and of ascorbate peroxidase; (iv) an increase of the level of thiobarbituric acid-reactive substances, assumed to reflect malondialdehyde formation arising from membrane lipid peroxidation. Thus, X. parietina might withstand realistic levels of Cd stress by: (1) intercepting the heavy metal at cell wall level, (2) the intervention of antioxidant metabolites, and (3) a moderate increase in guaiacol peroxidase activity.
在暴露于两种镉浓度（即4.5或9.0 μmol/L）的地衣石黄衣（Xanthoria parietina (L.) Th. Fr.）叶状体中，在24小时或48小时的暴露期内，测定了总镉和细胞壁结合镉以及主要抗氧化剂的含量。叶状体中的总镉含量在先前野外测量的范围内，并且与暴露浓度成正比，但与暴露持续时间的比例关系较小。总镉的一半以上被细胞壁固定。所采用的镉胁迫条件导致：（i）干重和蛋白质浓度没有变化；（ii）抗坏血酸水平升高，还原型谷胱甘肽水平降低，以及愈创木酚过氧化物酶活性增加；（iii）超氧化物歧化酶、过氧化氢酶、脱氢抗坏血酸还原酶、NADPH依赖的谷胱甘肽二硫化物还原酶、单脱氢抗坏血酸还原酶和抗坏血酸过氧化物酶的活性没有变化或略有降低；（iv）硫代巴比妥酸反应性物质水平升高，推测反映了膜脂过氧化产生的丙二醛形成。因此，石黄衣可能通过以下方式抵御实际水平的镉胁迫：（1）在细胞壁水平截留重金属；（2）抗氧化代谢物的干预；（3）愈创木酚过氧化物酶活性适度增加。
