Impact of active transport and transpiration on nickel and cadmium accumulation in the leaves of the Ni-hyperaccumulator Leptoplax emarginata: a biophysical approach

Abstract

Aims The primary aim of this study was to investigate the impact of active nickel and cadmium transport, transpiration and shoot biomass production on Ni and Cd accumulation in the leaves of the Ni-hyperaccumulator Leptoplax emarginata. A secondary objective was to observe the effects of various concentrations of nickel and cadmium in solutions on the plant growth and ecophysiological characteristics of these plants. Finally, the study sought to identify possible nickel and cadmium concentration gradients in solution as a function of the root distance. Methods The Intact Plant Transpiration Stream Concentration Factor (TSCF=xylem/solution solute concentration ratio) was determined for both Ni and Cd and for the selected intact transpiring Ni-hyperaccumulator Leptoplax emarginata, cultivated on two contrasting fertilized and Ni-Cd-contaminated sandy porous media (rhizotrons with central root compartments, linked to Mariotte tubes operated at −1 kPa). IPTSCF Ni and IPTSCF Cd were calculated as the ratios between the hyperaccumulator plant's nickel or cadmium mass in the leaves and the nickel or cadmium concentration in solution by the volume of water transpired during the period of culture. Plant growth characteristics and gas exchanges were also recorded.Results IPTSCF values were much greater than 1 (IPTSCF Ni =5.2±0.9 and IPTSCF Cd =4.4±0.6) whatever the amount of available Ni and Cd. This characterized a predominantly active plant metal uptake. Moreover, biological regulation was reported: plant growth and transpiration were significantly lower for hyperaccumulator plants cultivated in sand which was rich in available Ni and Cd, than for hyperaccumulator plants cultivated in topsoil, poor in available Ni and Cd. In the soil rhizosphere, capillary flow was related to transpiration and a depletion pattern was developed for Ni and sometimes for Cd. Conclusions Overall, the Intact Plant Transpiration Stream Concentration Factor appeared to be a relevant metal bioconcentration factor taking into account the predominant type of metal transport from roots to leaves, plant growth and transpiration coupling and metal availability. IPTSCF Ni and IPTSCF Cd values were much greater than 1 and similar whatever the amount of available Ni and Cd. This characterized a predominantly active plant combining Ni and Cd uptake and biological Plant Soil (2012) 350:99-115

Chrysotile Dissolution in the Rhizosphere of the Nickel Hyperaccumulator Leptoplax emarginata

“…But, most of the solubilized Mg and Fe were leached in the percolated solution, with L. emarginata absorbing a very small part of these elements (about 9% and 6% (estimation), respectively) in comparison with Ni (88%). These results suggested that the strong ability to hyperaccumulate Ni by L. emarginata as reported in controlled conditions 5,37 could act on chrysotile dissolution by inducing a sharp decrease of water-soluble Ni in the rhizosphere. We could not exclude that the release of Fe and Mg (only provided by chrysotile in the system and necessary for plant development) influenced initial chrysotile weathering process.…”

Role of transpiration in arsenic accumulation of hyperaccumulator Pteris vittata L.

“…Similar phenomenon was found for the nickel (Ni) hyperaccumulator Leptoplax emarginata (Bartoli et al 2012). In contrast, a significantly positive relationship is observed between the shoot Cd concentration and the transpiration of Phytolacca americana (Liu et al 2010).…”

“…We propose that, unlike the Ni hyperaccumulator L. emarginata (Bartoli et al 2012) or Cd hyperaccumulator S. alfredii, for the As hyperaccumulator P. vittata with its large biomass (∼9 t dry weight h m −2 year −1 ), transpiration is the main upward translocation process for As after the reduction of As(V) to As(III). This study aims to verify this hypothesis by investigating the role of transpiration in the As hyperaccumulation.…”

Tomato Accumulates Cadmium to a Concentration Independent of Plant Growth

“…Similarly, overabundance of Cd has been found to impede both shoot biomass and plant height in ornamental plants, as demonstrated by Liu et al [16] and Wu et al [17]. It is noteworthy that studies in wheat and Leptoplax emarginata have found that the transpiration rate affects plant height and shoot biomass, subsequently influencing the absorption of Cd [18,19]. This study aimed to examine the potential correlation between plant height and Cd accumulation in a sample of 31 tomato cultivars, and also to determine whether plants could influence Cd accumulation through physiological processes such as transpiration rate or photosynthesis.…”