Lead tolerance and physiological adaptation mechanism in roots of accumulating and non-accumulating ecotypes of Sedum alfredii
- 541 Downloads
Background, aim and scope
Lead (Pb) accumulation in soils affects plants primarily through their root systems. The aim of this study was to investigate early symptoms of the loss of membrane integrity and lipid peroxidation in root tissues and physiological adaptation mechanism to Pb in accumulating ecotypes (AE) and non-accumulating ecotypes (NAE) of Sedum alfredii under Pb stress in hydroponics.
Methods and results
Histochemical in situ analyses, fluorescence imaging, and normal physiological analysis were used in this study. Pb accumulation in roots of both AE and NAE increased linearly with increasing Pb levels (0–200 μM), and a significant difference between both ecotypes was noted. Both loss of plasma membrane integrity and lipid peroxidation in root tissues became serious with increasing Pb levels, maximum tolerable Pb level was 25 and 100 μM for NAE and AE, respectively. Pb supplied at a toxic level caused a burst of reactive oxygen species (ROS) in root cells in both ecotypes. However, the root cells of AE had inherently higher activities of superoxide dismutase (SOD), guaiacol peroxidase (POD), and lipoxygenase (LOX) in control plants, and the induction response of these antioxidant enzymes occurred at lower Pb level in AE than NAE. AE plants maintained higher ascorbic acid and H2O2 concentrations in root cells than NAE when exposed to different Pb levels, and Pb induced more increase in dehydroascorbate (DHA), catalase (CAT), and ascorbate peroxidase (APX) in AE than NAE roots.
Discussion and conclusion
Results indicate that histochemical in situ analyses of root cell death and lipid peroxidation under Pb short-term stress was sensitive, reliable, and fast. Higher tolerance in roots of accumulating ecotype under Pb stress did depend on effective free oxygen scavenging by making complex function of both constitutively higher activities and sensitive induction of key antioxidant enzymes in root cells of S. alfredii.
KeywordsHistochemical localization Phytoremediation Lead Roots Oxidative stress Sedum alfredii
Lead accumulating ecotypes of Sedum alfredii
5,5′-Dithiobis 2-nitrobenzoic acid
Lead non-accumulating ecotypes of Sedum alfredii
Reactive oxygen species
This work was supported by National Natural Science Foundation of China (30871589), the National High Technology Research and Development Program of China (2009AA06Z316), and Shanghai Tongji Gao Tingyao Environmental Science & Technology Development Foundation (7th winner, 2010). Authors are also grateful to two anonymous referees who made valuable suggestions on the manuscript.
- He B, Yang XE, Ni WZ, Wei YZ, Long XX, Ye ZQ (2002) Sedum alfredii: a new lead-accumulating ecotype. Acta Bot Sin 44(11):1365–1370Google Scholar
- Malecka A, Jarmuszkiewicz W, Tomaszewska B (2001) Antioxidative defense to lead stress in subcellular compartments of pea root cells. Acta Biochim Pol 48(3):687–698Google Scholar
- Rodriguez-Serrano M, Romero-Puertas MC, Zabalza A, Corpas FJ, Gomez M, Del Rio LA, Sandalio LM (2006) Cadmium effect on oxidative metabolism of pea (Pisum sativum L.) roots. Imaging of reactive oxygen species and nitric oxide accumulation in vivo. Plant Cell Environ 29(8):1532–1544CrossRefGoogle Scholar