Cadmium Uptake and Distribution to Edible Organs in African Indigenous Vegetables
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Date
2015
Authors
Onyuka, Enos
Husen, Wilhelm van
Nambafu, Godfrey N.
Bessler, Holger
Andika, Darius O.
Gweyi-Onyango, Joseph P.
Mwonga, Samuel
Ulrichs, Christian
Engels, Christof
Journal Title
Journal ISSN
Volume Title
Publisher
Tropentag
Abstract
Cadmium (Cd) is toxic to humans. The most important source for dietary intake is consumption
of plant products, whereby Cd concentrations in leafy vegetables are particularly high. In periurban
areas, soils are often contaminated with Cd. Thus, recommendations to increase vegetable
consumption should consider species-specific uptake and allocation to edible plant organs. Cadmium
uptake and distribution within plant was compared in various species to derive recommendations
for vegetable production on contaminated soils. Four African indigenous vegetable species (African
Nightshade Solanum scabrum, amaranth Amaranthus cruentus, cowpea Vigna unguiculata, spider
plant Cleome gynandra), and a standard species commonly grown in Asia (Pak Choi Brassica rapa
chinensis) were grown in nutrient solution at three Cd-concentrations: 0.1 (low), 1.0 (moderate)
and 2.5 μM Cd (high contamination). Biomass and mineral nutrient concentrations were measured
in roots, leaves, stems and lateral branches.
Growth was little affected by Cd supply with the exception of amaranth and cowpea. In these
species, growth of shoot organs was substantially reduced at moderate and high supply. Growth
depression was associated with low leaf iron concentrations indicating Cd-induced iron deficiency. In
all species Cd concentrations were higher in roots than in shoot organs, which is in accordance with
xylem loading being an important barrier for Cd distribution within plants. At moderate and high
supply, Cd concentrations in shoot organs strongly differed among species. Concentrations were
particularly low in cowpea, and high in amaranth and African Nightshade. Low Cd concentrations
in shoot organs of cowpea were associated with low apparent uptake and translocation rates of
Cd from roots to shoots. At all rates of Cd supply, Cd density in edible organs was significantly
influenced by species. Cadmium density was particularly low in cowpea and Pak Choi. Based on a
vegetable dish of 250 g fresh mass, best choice of species reduced Cd intake by 0.1 mg at low supply
(amaranth versus African Nightshade), 0.7 mg at moderate (cowpea versus African Nightshade)
and 1.7 mg at high Cd supply (cowpea versus
Description
A Conference Presentation
Keywords
Cd contamination, Cd toxicity, Dietary intake, Leafy vegetables, Peri-urban horticulture
Citation
Tropentag, September 16-18, 2015, Berlin, Germany