Differences in Copper Absorption and Accumulation between Copper-Exclusion and Copper-Enrichment Plants: A Comparison of Structure and Physiological Responses

Abstract

Differences in copper (Cu) absorption and transport, physiological responses and structural characteristics between two types of Cu-resistant plants, Oenothera glazioviana (Cu-exclusion type) and Elsholtzia haichowensis (Cu-enrichment type), were investigated in the present study. The results indicated the following: (1) After 50 μM Cu treatment, the Cu ratio in the xylem vessels of E. haichowensis increased by 60%. A Cu adsorption experiment indicated that O. glazioviana exhibited greater resistance to Cu, and Cu absorption and the shoot/root ratio of Cu were significantly lower in O. glazioviana than in E. haichowensis. (2) An analysis of the endogenous abscisic acid (ABA) variance and exogenous ABA treatment demonstrated that the ABA levels of both plants did not differ; exogenous ABA treatment clearly reduced Cu accumulation in both plants. (3) The leaf stomatal density of O. glazioviana was significantly less than that of E. haichowensis. Guard cells in E. haichowensis plants were covered with a thick cuticle layer, the epidermal hair was more numerous and longer, and the number of xylem conduits in the root was small. (4) The transpiration rate and the stomatal conductance of O. glazioviana were both significantly lower than those of E. haichowensis, regardless of whether the plants were treated with Cu. Taken together, these results indicate that the differences in the structural characteristics between these two plant species, particularly in the characteristics related to plant transpiration, are important factors that govern whether plants acquire or exclude Cu.

Copper Toxicity on Photosynthetic Responses and Root Morphology of Hymenaea courbaril L. (Caesalpinioideae)

“…These anatomical changes in leaves and roots possibly influenced the negative effect on gas exchange and, mainly, the root morphology of this tree. However, up to 200 mg kg −1 , Cu stimulates cuticle production in the leaves, which would possibly help these plants survive under stress conditions, such as drought due to decreased transpiration.This result resembles those found by Fu et al (2015).…”

“…Fibers are important in plants that are inserted in environments with metals, since lignin has adsorption sites of heavy metals (Lin et al 2005). Fu et al (2015) reported that the increase in Cu provided an increase in xylem vessels by 60% in E. haichowensis, which corroborates the increase in xylem vessels in the leaves of the studied tree.…”

Proteomic analysis on roots of Oenothera glazioviana under copper-stress conditions

“…Root samples were collected and immerged in 25 mM EDTA-Na solution for 15 min to desorb metal ions on root surfaces. Next, root and leaf samples were washed thoroughly with tap water, rinsed with deionized water, cleaned with tissue paper, dried in an oven at 120 °C for 0.5 h to deactivate enzymes, and stored at 80 °C for 24 h. Next, these samples were ground to a fine powder, and 0.2 g was separately digested using an acid mixture of HNO 3 /HClO 4 (87:13, v:v) 67 . The digests were dissolved in 5% HNO 3 for Cu analysis using a NOVA 300 atomic absorption spectrophotometer (Analytik, Jena, Germany).…”

Thirteen decades of antimicrobial copper compounds applied in agriculture. A review

“…The level of adherence of these compounds on plant surfaces depends on a number of factors including the type of leaf surface (smooth versus rough) and weather conditions in Cu solubility by forming weak acids that lower the pH of the water on the plant surface, which increases Cu solubility and availability (Arman and Wain 1958). In addition, differences in the structural characteristics of plants-including stomatal density, cuticle layer thickness, and epidermal hairs density-affect the absorption of Cu ions by leaf surfaces (Fu et al 2015).…”