PHYSIOLOGICAL STUDIES ON THE HEAVY METALS RESISTANCE MECHANISMS IN TOMATO PLANTS GROWING UNDER INTERCROPPING CONDITIONS.

Abstract

Pot experiments were conducted in the greenhouse of the Faculty of Agriculture in Shebin El-Kom, Menoufia University, during 2018 and 2019 seasons, to study the cultivation of (sensitive) tomato plants in a loading system with watercress plants (resistant) in a soil contaminated with heavy metals. Three levels of lead were used, which are 0 (control), 1000 and 2000 mg / kg of soil, and three levels of cadmium metal, which are 0 (control), 100 and 300 mg / kg of soil, each alone. Use of growth inducers as nanoparticles silicon and seaweed extract and its affects on tomato or watercress plants under heavy metals stress. The characteristics of vegetative growth and some of the physiological and chemical characteristics such as photosynthetic pigments, water relations, activity of some antioxidant enzymes, Pb and Cd accumulation and some quantitative and qualitative characteristics of the yield were studied. The soil contamination with lead and cadmium minerals at all levels led to a decrease in all studied parameters. There was an increase in the accumulation of lead and cadmium metal within watercress plants by increasing the concentrations of lead and cadmium in the contaminated soil, and there was a decrease of the heavy metals residual in the polluted soil. Spraying with silicon and seaweed extract on tomato plants increased the vegetative growth characteristics, relative water content, plant pigments, yield and its components for tomato plants. While it led to a decrease in the concentration of the enzymatic activity of peroxidase and phenoloxidase. Also, increased the efficiency of watercress plants' accumulation of heavy metals.From the above, it is cleared that the use of hyperaccumulators plants (watercress) to accumulate heavy metals led to a decrease in the residual of the two heavy metals, lead and cadmium, in the contaminated soil, and this led to a better growth conditions for tomato plants grown in the intercropping system with watercress plants in soil contaminated with lead and cadmium.