Iron (Fe) is an essential
element for plants; however, plants face Fe deficiency in neutral and alkaline
soils because ferric iron, despite being abundant in the Earth’s crust, is
almost insoluble and therefore unavailable to plant roots. A potentially important aspect of Fe deficiency is its relationship to
the availability and uptake of other metal ions. Copper (Cu) is also an essential
element for plants, being involved in various redox reactions, including electron
transfer; however, the toxicity of excess Cu to organisms has been widely
recognized because Cu produces reactive oxygen species such as hydroxyl
radicals, which cause oxidative damage to lipids, proteins and DNA, resulting
in cellular deterioration.
Hyoscyamus albus (Solanaceae, white henbane) is an annual or biennial plant growing on
the Continent, particularly in France and in Indian subcontinent, and used as a
source of hyoscyamine, which is an important anticholinergic drug of plant
origin.
In this paper, seedlings
of the medicinal plant Hyoscyamus albus
were supplied with an excess of Cu to examine the possible application in
phytoremediation. The seedlings were cultured in B5 medium supplied with basal
0.1 μM Cu and 200 μM Cu under various light conditions: short day (SD); long
day (LD); and continuous light (CL). In addition, the effect of supplying 200
μM Cu under Fe deficiency was determined, in order to elucidate the interaction
between Cu and Fe. All results were expressed as means and sd. Statistical
significance was assessed by ANOVA, followed by Dunnett’s multiple comparison
tests (Excel Statistics, SSRI, Tokyo, Japan).
The results
indicated that Fe-deficiency symptoms that developed in plants grown with basic
levels of Cu under LD almost disappeared when excess Cu was supplied. Plant
growth mainly depended on the photo irradiation period (SD < LD~CL); and 200
μM Cu did not inhibit growth at all when Fe was available, whereas in the
absence of Fe, CL caused damage to growth. Analysis of the Cu and Fe contents
of the plants revealed that Cu was distributed equally in both the aerial parts
and roots, whereas most of the Fe was found in the roots; under Fe deficiency,
Cu accumulation in the roots apparently increased. Cu was mainly distributed in
the soluble fraction, which included vacuoles and the cell-wall fraction.
In conclusion, these
results provide evidence indicating that H.
albus seedlings are tolerant of Cu present in excess. Furthermore, excess
Cu was able to compensate for Fe deficiency, depending on the light conditions.
Continuous light inhibited this effect, probably as a result of the induction
of Mn deficiency.
Article by Noriko
Tamari, et al, from Nagasaki University, Nagasaki, Japan.
Full access: http://mrw.so/5hg2p6
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