BIOCHEMICAL STUDIES ON THE EFFECT OF LEAD AND CADMIUM ON TOMATO PLANT

Abstract

The effect of lead and cadmium on tomato (Lycopersicom eseulentum Mill) type (Castle Rock ),seedlings was studied .Pb and Cd was added to the water suppling the plant , the nutrient water was treated with there heavy metals for 3 months during the growth period and it was stopped as soon as the fruits were developed . The following concentration were used I ,5 , I 0 ,50 , I 00 ppm . There are a general decreases in number of leaves ,number of branches per plant ,number of fruits per plant and fresh weight of fruits in tomato treated with lead and cadmium . lead accumulations in the roots ,response to 50 ,100 ppm Pb treatment were 66.6 and 94.2 ppm , while in the shoots were 30.65 and 36.35 respectively. The lead concentration increased to a great extent in the leaves in response to lead treatment which reachedl6.8, 38.7and 51.5 ppm on response to 10, 50 and IOOppm lead treatment, respectively. The lead concentration in the fruits increased from 0.24 ppm in the control plant ,and I 0.6 ,14.0 andl4.9ppm in response to 10 ,50 ppm and 100 ppm lead treatment , respectively. The accumulations of cadmium in different plant part of tomato plants cadmium accumulation in the roots ,response to 50 , I 00 ppm pb treatment were 81.6 and 212.1 ppm , while in the shoots were 16.24 and 50.54, respectively. The cadmium concentration increased to a great extent in the leaves in response to lead treatment which it reached 18.8 , 81.66 and 128.67 ppm on response to 10 ,50 and IOOppm cadmium treatment respectively. The cadmium concentration in the fruits increased from 0.82 ppm in the control plant to 2.11, 1.22 and 4.12ppm in response to I 0 ,50 ppm and I 00 ppm cadmium treatment respectively. The effect of lead and cadmium on chlorophyll (a , band the total ) contents in tomato leaves treatments at 50 and I 00 ppm caused a significant reduction in the chlorophyll a , chlorophyll b and total .Studying the chemical composition of the plant total carbohydrates total soluble sugars and reducing sugars and non reducing sugars content was decreased with increasing of lead and cadmium treatments . Lead and cadmium treatments had non significant effect on free amino acids in tomato fruits , but , increased some amino acids such as proline ,tyrosine ,valine ,lysine , and threonine Other amino acids ( Aspartic acid ,glutamic acid , serine ,arginine ,alanine , methionine , isoleucine ,leucine ,phenylalanine , histidine and glyceine ) • A general increase in peroxidase and polyphenol oxidase activity in all lead and cadmium treatments at I, 5 , I 0 , 50 and I 00 ppm increasing enzyme activity with increasing lead and cadmium treatments.