Re: Would heavy metal compounds alter development of green plant pigments

Complete question:

I am currently embarking on a school investigation into the affect of heavy 
metal compounds on plant development, specifically lead compounds with mung 
bean seeds. I am currently only looking at changes in dry mass compared to a 
control, but could also examine the affect on pigments (eg chlorophil) by paper 
chromatography. I would like to know if there is likely to be any affect with 
any heavy metals that would cause visible effects. Thanks for your help and 
time. 


Reply:

Lead is usually not absorbed in large amounts by soil-grown plants. Also, the 
lead that is absorbed mostly remains in the roots. Lead toxicity in plants is 
not common under natural conditions but may be an indirect effect of the lead 
reducing uptake of other cations, especially calcium. Bergmann (1992) notes 
that lead toxicity may disrupt calcium metabolism. However, calcium deficiency 
does not usually result in chlorosis. Bergmann has photos of leaf chlorosis 
symptoms for toxicities of cadmium, zinc, copper and nickel. 

Heavy metals that most affect chlorophyll are the essential heavy metals, such 
as iron, copper, zinc and manganese. Deficiencies of these usually result in 
chlorosis. Iron deficiency is termed "iron chlorosis" because of its major 
effect on chlorophyll synthesis. Iron deficiency is easy to induce in plants 
grown in hydroponics (solution culture); houseplants work well and can lower 
the nutrient solution pH by 3 or 4 units when they become iron deficient 
(Hershey 1995). 


References


Lead in the Home Garden and
Urban Soil Environment


Comparative Lead Uptake and Responses of Some 
Plants Grown on Lead Contaminated Soils

Bergmann, W. 1992. Nutritional Disorders of Plants. New York: Gustav Fischer.

Hershey, D.R. 1995. Plant Biology Science Projects. New York: Wiley.