Abstract
Hydroponic experiments were conducted to investigate the variation of root exudates from the hyperaccumulator Sedum alfredii under the stress of cadmium (Cd). S. alfredii was cultured for 4 days in the nutrient solution spiked with CdCl2 at concentrations of 0, 5, 10, 40, and 400 µM Cd after the pre-culture. The root exudates were collected and analyzed by GC-MS, and 62 compounds were identified. Of these compounds, the orthogonal partial least-squares discrimination analysis (OPLS-DA) showed that there were a distinct difference among the root exudates with different Cd treatments and 20 compounds resulting in this difference were found out. Changing tendencies in the relative content of these 20 compounds under the different Cd treatments were analyzed. These results indicated that trehalose, erythritol, naphthalene, d-pinitol and n-octacosane might be closely related to the Cd stabilization, phosphoric acid, tetradecanoic acid, oxalic acid, threonic acid and glycine could be attributed to the Cd mobilization, and mannitol, oleic acid, 3-hydroxybutanoic acid, fructose, octacosanol and ribitol could copy well with the Cd stress.
Highlights
Root exudates from a plant are plant metabolites that are released to root surfaces or into the rhizosphere to enhance plant nutrient uptake or copy with environment stresses [1,2,3]
Greater tolerances of a plant to high concentrations of generally toxic metals, as well as hyperaccumulation of metals in aerial parts of a plant are typical characteristics of a hyperaccumulator [38,39,40,41]. These characteristics of S. alfredii were confirmed in this study, and the results presented are highly consistent with the results from the previous study [26,27,28,29,30]
An investigation on the components of root exudates was performed in S. alfredii and contrasted with that in different Cd exposed concentrations in order to reveal possible mechanisms of a Cd-hyperaccumulator
Summary
Root exudates from a plant are plant metabolites that are released to root surfaces or into the rhizosphere to enhance plant nutrient uptake or copy with environment stresses [1,2,3]. They are generally classified into two types, namely, high molecular weight (HMW) and low molecular weight (LMW) materials. The former includes mucilage (mainly polysaccharides and polyuronic acid) and ectoenzymes; the latter mainly consists of organic acids, sugars, phenols and PLOS ONE | DOI:10.1371/journal.pone.0115581. Phytoremediation has become a research focus recently because it is a costeffective and environment friendly technique [6, 8]
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