Cadmium induces hypodermal periderm formation in the roots of the monocotyledonous medicinal plant Merwilla plumbea.
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Date
2010
Journal Title
Journal ISSN
Volume Title
Publisher
Annals of Botany Company.
Abstract
Background and Aims. Merwilla plumbea is an important African medicinal plant. As the plants grow in soils
contaminated with metals from mining activities, the danger of human intoxication exists. An experiment with
plants exposed to cadmium (Cd) was performed to investigate the response of M. plumbea to this heavy metal, its
uptake and translocation to plant organs and reaction of root tissues.
Methods. Plants grown from seeds were cultivated in controlled conditions. Hydroponic cultivation is not suitable
for this species as roots do not tolerate aquatic conditions, and additional stress by Cd treatment results in
total root growth inhibition and death. After cultivation in perlite the plants exposed to 1 and 5 mg Cd L-1 in
half-strength Hoagland’s solution were compared with control plants. Growth parameters were evaluated, Cd
content was determined by inductively coupled plasma mass spectroscopy (ICP-MS) and root structure was
investigated using various staining procedures, including the fluorescent stain Fluorol yellow 088 to detect
suberin deposition in cell walls.
Key Results. The plants exposed to Cd were significantly reduced in growth. Most of the Cd taken up by plants
after 4 weeks cultivation was retained in roots, and only a small amount was translocated to bulbs and leaves. In
reaction to higher Cd concentrations, roots developed a hypodermal periderm close to the root tip. Cells produced
by cork cambium impregnate their cell walls by suberin.
Conclusions. It is suggested that the hypodermal periderm is developed in young root parts in reaction to Cd
toxicity to protect the root from radial uptake of Cd ions. Secondary meristems are usually not present in monocotyledonous
species. Another interpretation explaining formation of protective suberized layers as a result of
periclinal divisions of the hypodermis is discussed. This process may represent an as yet unknown defence reaction
of roots when exposed to elemental stress.
Description
Keywords
Cadmium--Environmental aspects., Merwilla Plumbea., Medicinal plants--South Africa.
Citation
Lux, A. et al. 2011. Cadmium induces hypodermal periderm formation in the roots of the monocotyledonous medicinal plant Merwilla plumbea. Annals of Botany 107 (2) pp. 285-292.