Document Type : Original Article
Author
Horticulture Department-, Faculty of Agriculture- Damnhoure University.
Abstract
This experiment was conducted to study the response of tomato plants (Solanum lycopersicum L. cv. 'Thuria') to different levels of copper and to reduce the harmful effects of high levels. The plants were grown during two summer seasons between March and July (2022) and repeated between March and July (2023) on a private soilless farm in New Noubaria City, Beheira Governorate. The plants were grown in sandy and peat moss as substrate, copper was added to the tomato plants through the nutrient solution. The Cu concentrations in the nutrient solutions were: control 48 ppb (the Cu concentration in the standard irrigation solution), 96 ppb, 144 ppb, and 192 ppb. On the other hand, protective treatments tested as foliar sprays are proline (Pro1) 40 mmol, proline (Pro2) 80 mmol, melatonin (MT1) 50 µmol, melatonin (MT2) 100 µmol, and the control distilled water. The results obtained from the two seasons indicated that increasing the Cu concentration led to a significant decrease in the fresh weight of roots and aerial parts, fresh and dry weight of the tomato plant, number of fruits per plant, average fruit weight, and plant productivity in both seasons. The highest mean values for the previous characteristics were achieved by applying Cu at 48 ppb (control treatment). However, the lowest mean values were obtained with the application of Cu at 192 ppb. Regarding the elemental content of tomato plants, the results showed that leaf nitrogen, phosphorus, and potassium contents decreased. In contrast, Cu contents in roots, stems, leaves, and fruits increased with increasing Cu concentrations in the nutrient solution. The chlorophyll content in leaves increased from 48 ppb to 96 ppb copper, decreasing sharply with increasing Cu concentration up to 192 ppb. Meanwhile, the protein and proline contents of the leaves decreased as the Cu concentration increased. The roots and leaf's contents of hydrogen peroxide, MDA, catalase enzyme activity, and superoxide dismutase increased with increasing Cu concentration. However, using proline (Pro1) 40 mmol, proline (Pro2) 80 mmol, melatonin (MT1) 50 μmol, and melatonin (MT2) 100 μmol, led to the plant's leaves having more nitrogen, phosphorus, potassium, and chlorophyll, which was reflected in improved plant growth characteristics compared with the control under different copper levels. It also improved the antioxidant content in the roots and leaves, which helped increase the number of fruits per plant, average fruit weight, and plant productivity. The outcome of this research suggested the possibility of using 100 μmol melatonin (MT2) and proline(Pro2) 80 mmol to reduce the harmful effects of excess copper in tomato plants.
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