Kumar and Saritha

enzymes and (II) it can intensify the processes of reactive oxygen species (ROS)

production leading to oxidative stress (Prasad et al. , 1999). Reactive oxygen

species produced can damage photosystem reaction center proteins by which

photosynthesis could decrease and cause viability loss in the cells.

Plants initiate a signal transduction pathway that triggers enzymatic and non-

enzymatic antioxidative systems that detoxify the cells (Dalton, 1995). In

this mechanisms a wide series of enzymes exist in plants that serve to remove

ROS, such as peroxidase, superoxidedismutases, ascorbate peroxidase, catalase,

phenylalanine ammonialyase, ascorbicacidoxidase etc. (Verma and Dubey, 2003)

thereby preventing the formation of OH radicals. These non-enzymatic and

enzymatic systems in plant together keep the reactive oxygen species in low levels

and not to be injured by accumulation of ROS. The purpose of this research is to

exploit the ability of various plant species to thrive in high lead environments and

its affect on antioxidative defense mechanism.

materials and methods

Study site

Lead contaminated industrial site (estimated production of about 12 tons per

annum) and Pb free site (nearby forest) located at Tirupati, India is selected as

a study site which is occupied by luxuriant natural vegetation. Selected weeds

with abundant growth (a) Calotropis procera (b) Ipomea purpurea (c) Eichornia

fasiculata (d) Parthenium histocarpus (e) Bromus tectorum (f) Anisomilus

molabarica were collected from lead contaminated industrial area and nearby lead

free site and samples of spoils were taken for laboratory analysis. Pb-contaminated

soils were collected from an industrial site. The soil was screened to pass through

a 1.0 cm sieve and thoroughly mixed before use. The following procedures were

used to characterize the soil. Soil p H was measured using 1:1 soil/ water ratio;

total soil Pb was determined by the atomic absorption spectrophotometer, organic

matter content was measured by the Walkley Black method and particle size

was measured by the hydrometer method. The selected physical and chemical

properties of the Pb-contaminated soils are presented in Table 1.

Total chlorophyll content

Chlorophyll extraction was done according to method described by Wintermans

and De Mots (1965) and expressed in mg g -1 FW.

TBARS assay

A TBARS(Thiobarbituricacidreactivesubstances)assaywasperformedfollowing

the method of Heath and Packer (1968).

14

Int. J. Bioinformatics and Biological Sci.: v.2 n.1&2, p. 13-22. March & June 2014