Distribution and chemical forms of copper in the root cells of castor seedlings and their tolerance to copper phytotoxicity in hydroponic culture

Abstract

The subcellular localization and chemical forms of copper in castor (Ricinus communis L.) seedlings grown in hydroponic nutrient solution were identified by chemical extraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The wild castor seeds were harvested from an abandoned copper mine in Tonglu Mountain, Daye City of Hubei Province, China. The results revealed that (1) the seedlings grew naturally in MS liquid medium with 40.00 mg kg(-1) CuSO4, in which the seedling growth rate and biomass index were 0.14 and 1.23, respectively, which were the highest values among all the treatments. The copper content in castor seedlings increased along with elevated CuSO4 concentration in the medium, reaching a maximum value of 16 570.12 mg kg(-1)(DW) when exposed to 60.00 mg L(-1) CuSO4, where 91.31% of the copper was accumulated in roots. (2) The copper existed in various chemical forms in the roots of the castor seedlings. Copper of 67.66% was extracted from the components of cell walls, such as exchangeable acidic polar compounds, cellulose and lignin, protein and pectin, and less concentrated in cell cytoplasm and nuclei. (3) Furthermore, the root cell walls were thickened when the castor seedlings exposed to CuSO4, with a large amount of high-density electron bodies, attached to the thickened cell walls. In the cell walls, most copper was bound to the carboxyl (-COOH) and hydroxyl (-OH) groups of acidic polar compounds, cellulose, hemicellulose, and polysaccharides. The conclusion showed that castor exhibited a strong tolerance to copper, the copper were accumulated mainly in the root cell, the root cell walls of castor were the major location of patience and detoxification in copper stress.

The effect of excess copper on growth and physiology of important food crops: a review

“…The mechanism of Cu uptake is initiated by the adsorption of Cu on the root surface from where it dissociates from its complex forms before absorption by plants ( Kabata-Pendias and Pendias 1992). The root apoplast is a major metal accumulation compartment in plants (Krzeslowska 2011).…”

Growth of Brachiaria decumbens in Latosol contaminated with copper

“…Fageria (2001) has found copper toxicity in soil treated with doses above 51 mg kg -1 for rice; 37 mg kg -1 , for beans; 48 mg kg -1 , for maize; 15 mg kg -1 , for soybeans; and 51 mg kg -1 , for wheat. The better growth and accumulation of biomass in seedlings of Ricinus communis L. was found in 40 mg L -1 of CuSO4, and the largest copper content in seedlings was found at a concentration of 60 mg L -1 CuSO4 (Kang et al, 2015).…”

Frugivorous bird characteristic of seed disperser in shrubland tropical forest West Java, Indonesia

“…It may be due to the thickening of the roots. Root thickening has been reported by some authors in response to metal toxicity, such as aluminum (Alvarez et al 2012), iron (Fu et al 2012), silicon (Fu et al 2012), and cadmium (Felici et al 2014), and copper (Kang et al 2015).…”