1Allaway W H, 1968. Agronomic controls over the environmental recycling of trace element. Advance in Agronomy, 2: 235- 274.
2Alloway B J, Steinnes E, 1999. Anthropogenic additions of cadmium soils. In: Cadmium in Soils and Plants (Machlaughin M J, Singh B R, eds.). The Netherlands: Kluwer Academic Publishers. 97-118.
3Alloway B J, 1995. Soil processes and the behaviour of heavy metals. In: Heavy Metals in Soils (Alloway B J, ed.). London: Chapman & Hill.
4Amon D J, 1956. Chlorophyll absorption spectrum and quantitative determination. Biochimical and Biophysical Acta, 20: 449-461.
5Atta S, Maltese S, Marget P, Coussin R, 2004. (NO3)-N-15 assimilation by the field pea Pisum sativum L. Agronomy, 24: 85-92.
6Baszynski T, Tukendorf M, Ruszkowska M, Skorzynska E, Maksymiec W, 1988. Characteristics of the photosynthetic apparatus of copper non-tolerant spinach exposed to excess copper. Journal of Plant Physiology, 132: 708-713.
7Buchauer M J, 1973. Contamination of soil and vegetation near a zinc smelter by zinc, cadmium, copper and lead. Environmental Science and Technology, 7: 131-135.
8Chugh L K, Sawhney S K, 1999. Photosynthetic activities of Pisum sativum seedlings grown in presence of cadmium. Plant Physiology and Biochemistry, 37: 297-303.
9Das P, Samantaray S, Rout G R, 1997. Studies on cadmium toxicity in plants: A review. Environmental Pollution, 98: 29-36.
10Devi S R, Prasad M N V, 1998. Copper toxicity in Ceratophyl- lure demersum L. (Coontail), a free floating macrophyte: responses of antioxidant enzymes and antioxidants. Plant Science, 138: 157-165.