Kumar and Saritha

fig. 3 and 4: Effects of Pb concentration on catalase activity, and

Phenylalanineammonialyase activity

Effect of Pb on Phenylalanineammonialyase activity

Increased Phenylalanineammonialyase activity could be a response to the

cellular damage provoked by higher Pb concentrations. Unsurprisingly,

phenylalanineammonialyasewasmoreactivatedbythepresenceoflead.Significant

increase was observed by 20% to 48% in all the plants in compared with controls.

Parthenium histocarpus showed highest increase in phenylalanineammonialyase

activity by 48% and lowest is seen in Ipomea purpurea (20%) followed by

Anisomilius molabarica (46%), Calotropis procera (42%), Eichornia fasculata

(37%) and Bromus tectorum (36%) compared with controls (Fig. 5). Overall

phenylalanineammonialyase activity was elevated in all plants. Activation of PAL

and lignin content increase is considered as common plant responses to various

stress factors, including heavy metals (Yang et al., 2007; Kovacik and Klejdus

2008). So it seems that in weed plants the increase of PAL activity is efficient in

catalyzing deamination reaction of the amino acid phenyl alanine at the gateway

from the primary metabolism into the important secondary phenylpropanoid /

phenolic metabolism in plants (Hahlbrock and Scheel, 1989). Overall, Pb had

the high inducement on Phenylalanineammonialyase. Similar observations were

recorded in previous study under Nacl stress according to Simaei et al., (2012) in

Soybean Plants, rice under cadmium toxicity (Ting Hsu and Huei Kao, 2004) and

Luffa cylindrical under lead toxicity (Jiang et al., 2010).

Effect of Pb on Ascorbic acid oxidase activity

In our experiment, the exposure of plants to lead doses resulted, in decreased

ascorbicacidoxidase content from 68% to 6% in all the plants compared with

18

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