The effect of cadmium and lead pollution on growth and physiological parameters of field beans (Vicia faba)

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Date
2019Author
Alle, V.
Osvalde, A.
Vikmane, M.
Kondratovics, U.
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Research on the impact of soil contamination on crops is important as plants directly
take up heavy metals from the soil through the roots, so heavy metals can enter the food chain.
The aim of this study was to investigate the impact of cadmium (Cd) and lead (Pb) pollution on
growth and physiological parameters of field beans. Plants in the vegetation experiment were
grown under controlled conditions. Changes in growth and physiological parameters were studied
at five levels of Cd (0–25 mg L
-1
) and at 6 levels of Pb in substrate: from (0–1,000 mg L
-1
) at the
first day of the experiment, to (0–2,000 mg L
-1
) at the end of the experiment after gradual Pb
additions after every sample collecting day. Methods used for analysing the plant material: the
content of amino acid proline and photosynthetic pigments were determined by
spectrophotometry; chlorophyll a fluorescence parameters – using continuous excitation
chlorophyll fluorimeter. The fresh weight of plant above-ground parts and roots was detected.
The growth and development of field beans was slightly influenced by increasing amount of Cd
and Pb in substrate only at the end of the experiment. The highest Cd treatments (Cd20 and Cd25)
caused 2.5 and 1.3 times increased proline concentration in bean leaves. The chlorophyll a + b
content and chlorophyll a fluorescence parameter Fv/Fm changed differently throughout the
experiment. In general, during the experiment, there was a tendency for the content of proline in
leaves for Pb treatments to be increased compared to control. At the end of the experiment the
content of proline in field bean leaves of the highest Pb treatments (Pb600 + 100 + 400 + 500,
Pb800 + 100 + 400 + 500 and Pb 1,000 + 100 + 400 + 500) was 1.66, 1.44 and 1.55 times higher,
respectively, than that of the control plant leaves. The negative impact of exposure to Pb on
chlorophyll a + b, chlorophyll a fluorescence parameter PIndex and Fv/Fm in bean leaves was less
pronounced compared to Cd. The obtained results confirm that field beans until their flowering
stage can grow and develop in the presence of a large amount of Cd and Pb in substrate without
significant growth inhibition and detrimental impact on physiological parameters, if optimal
cultivation conditions are provided.