Abstract
Phytoextraction of Cd is a growing biotechnology although we currently know few Cd hyperaccumulators, i.e., plant species able to accumulate at least 0.1mg Cdg(-1) dry weight in aerial organs. Owing their deep root system and high biomass, trees are more and more preferred to herbaceous species for phytoextraction. Assuming that conifers could be relevant models under cold climates, we investigated cadmium tolerance of the hybrid larch Larix × eurolepis Henry (Larix decidua × Larix kaempferi) and the efficiency of this species to store this metal. In vitro grown larches were chosen in order to reduce time of exposure and to more rapidly evaluate their potential efficiency to accumulate Cd. One-month-old plantlets were exposed for 2 and 4weeks to 250 and 500μM Cd. Results showed that they tolerated a 4-week exposure to 250μM Cd, whereas the content of photosynthetic pigment strongly dropped in plantlets growing in the presence of 500μM Cd. In the presence of 250μM Cd, shoot growth slightly decreased but photosynthetic pigment and total soluble carbohydrate contents were not modified and no lipid peroxidation was detected. In addition, these plantlets accumulated proline, particularly in shoots (two to three times more than control). In roots, Cd concentration in the intracellular fraction was always higher than in the cell wall fraction contrary to shoots where Cd concentration in the cell wall fraction increased with time and Cd concentration in the medium. In shoots, Cd concentration was lower than in roots with a ratio of 0.2 after 4weeks of exposure but stayed around 0.2mgg(-1) dry weight, thus a value higher than the threshold requested for Cd hyperaccumulators. Hybrid larch would thus be a relevant candidate for field test of Cd phytoextraction.
Highlights
Douglas fir (Pseudotsuga menziesii (Mirb.)) is a coniferous species native of the West Coast of NorthAmerica and is one of the most important worldwide timber species
The accumulation of Al in Pinus massoniana was mainly detected in roots (374 μg g−1 ), and only small amounts of Al were detected in the aerial parts (24.2 μg g−1 DW and 87.8 μg g−1 DW of stems and leaves, respectively) when treated with a concentration of 10 μM AlCl3 over 40 days [6]. These results are equivalent to the data reported. These results suggest that a concentration of 200 μM AlCl3 can be defined as the tolerance threshold for Douglas fir somatic plantlets, as higher concentrations lead to a drop in dry weight accompanied with a reduction in root elongation
This study showed, for the first time, that in vitro-grown Douglas fir somatic plantlets, exposed since germination to Al stress, tolerate relatively high Al concentration in the culture medium in comparison with crop species
Summary
Douglas fir (Pseudotsuga menziesii (Mirb.)) is a coniferous species native of the West Coast of NorthAmerica and is one of the most important worldwide timber species. In Europe, it is frequently used to satisfy an increasing demand for its wood, which presents outstanding mechanical properties and durability. This species has been largely planted since the mid-20th century [1]. In opposition to deciduous forests, large coniferous plantations might have deleterious effects on woodland, notably because the slow litter decomposition leads to an acidification of the soil, which, in turn, increases the mobility of some elements. Insoluble aluminum hydroxides (e.g., Al(OH)3 ), mostly present in neutral soils, give rise to the highly soluble Al3+ free species when pH drops to 5 or below.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
