Subcellular distribution and chemical form of Pb in hyperaccumulator Arenaria orbiculata and response of root exudates to Pb addition

• Published in: Frontiers of environmental science & engineering 2015-04, Vol.9 (2), p.250-258
• Main Authors: Zu, Yanqun, Li, Yuan, Min, Huan, Zhan, Fangdong, Qin, Li, Wang, Jixiu
• Format: Article
• Language: English
• Subjects: absorption; Accumulation; Acetic acid; Amino acids; Arenaria; Arenaria orbiculata; Cell culture; Cell walls; chemical forms; Citric acid; Drug tolerance; Earth and Environmental Science; Environment; Ethanol; Exudates; Exudation; Fractions; free amino acids; hydrochloric acid; Hydrogen chloride; hydroponic culture; Lead; Low molecular weights; Malic acid; Molecular weight; Organic acids; Research Article; root exudates; Roots; Shoots; Sodium chloride; Soil ecology; subcellular distribution; subcellular fractions; Sugar; sugars; Tartaric acid; 亚细胞分布; 亚细胞组分; 低分子量有机酸; 化学形态; 根系分泌物; 游离氨基酸含量; 超富集植物; 铅含量
• ISSN: 2095-2201; 2095-221X
• DOI: 10.1007/s11783-014-0643-3

Solution culture was conducted in order to understand accumulation characteristics and chemical forms of Pb in Arenaria orbiculata （A. orbiculata） and the response of root exudates to Pb addition. The results showed that： 1） Pb contents in the shoot and root of A. orbiculata increased with increasing in Pb concentrations in solution. 2） The contents of Pb chemical forms under Pb addition followed as： HAc extractable fraction＇（FriAC）〉 HC1 extractable fraction （FHcl）〉 NaCl extractable fraction （FNacl） 〉 ethanol-extractable fraction （FE） 〉 water extractable fraction （Fw）. 3） Increased Pb level in the medium caused increases in Pb contents in the four subcellular fractions of shoots and roots, with most accumulation in FIV （Fraction ＇IV, sbluble fraction） in shoots and FI （Fraction I, cell wall fraction） in roots. 4） Contents of soluble sugar and free amino acid of root exudates increased with increasing Pb concentration in solution. Significantly positive correlations between Pb and contents of soluble sugar and free amino acid were observed. 5） With Pb concentrations in solution, low molecular weight organic acids （LMWOAs） contents followed the tendency： tartaric acid 〉 acetic acid 〉 malic acid 〉 citric acid. Significantly positive correlation was observed between Pb and citric acid contents. The results indicate that soluble sugars, free amino acid and citric acid in root exudates of A.orbiculata facilitate the absorption and accumulation of Pb, which exist in NaCl-, HCI- and HAc- extractable Pb forms, FI and FIV fractions, resulting in tolerance of A.orbiculata to Pb.