Potted experiments were conducted in the greenhouse of the College of Agriculture in Shebin El-Kom, Menoufia University, during the 2018 and 2019 seasons, to study the cultivation of (sensitive) tomato plants in a loading system with watercress plants (resistant) in a land contaminated with heavy metals. Treating the soil contaminated with heavy metals by growing voracious plants to absorb these minerals, which are watercress. Study the rate of absorption and transfer of lead and cadmium from soil to watercress plants in mg / kg soil. Study the effect of heavy elements on growth, water relations and chemical content, as well as yield and components of tomato plants. The use of growth promoters such as silicon and seaweed extract and how they affect tomato or watercress plants. Three levels of lead were used, which are 0 (control), 1000 and 2000 mg / kg of soil, and contamination using three levels of cadmium metal, which are 0 (control), 100 and 300 mg / kg of soil, each alone.
The characteristics of vegetative growth and some of the physiological and chemical characteristics such as photosynthetic pigments, water relations, total sugars, proline concentration, activity of some enzymes, total protein, plant content of some mineral elements, and some quantitative and qualitative characteristics of the crop were studied.
The soil contamination with lead and cadmium minerals at all levels of lead and cadmium contamination led to a decrease in vegetative growth characteristics, total and relative water content, plant pigments, nitrogen, phosphorous and potassium concentration, and lack of yield and its components for tomato plants. While it led to an increase in proline concentration and the enzymatic activity of peroxidase and phenol oxidase.
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. In addition, there is a lack of the remaining heavy elements in the polluted soil.
Spraying with silicon and seaweed extract on tomato plants increased the vegetative growth characteristics, total and relative water content, plant pigments, nitrogen, phosphorus and potassium concentration, yield and its components for tomato plants. While it led to a decrease in the concentration of proline and the enzymatic activity of peroxidase and phenol oxidase. Also, spraying with growth stimuli increased the efficiency of watercress plants' absorption of heavy elements.
From the above, it is clear that the use of heavy metals (watercress) to absorb heavy metals led to a decrease in the concentration of the two heavy metals, lead and cadmium, in the contaminated soil, and this led to better growth conditions for tomato plants grown in the loading system with watercress plants in soil contaminated with lead and cadmium.