This experiment was carried out in Medicinal and Aromatic Plants Research Station at EL-Kanater EL-Khayria, Horticultural Research Institute, Agricultural Research Center, in two successive seasons; 1998 and 1999. The trace elements used in this experiment were Zn, B and Mo. Zn or B used at the rates of 0, 25, 50 or 100 ppm, while Mo at 0, 5, 10 or 20 ppm. The plants were treated with the microelements as foliar spray on April 22nd, July 7th and October 23rd. The obtained results can be summarized as follows: Spraying the plants with B at 100 ppm resulted in the greatest plant height and number of branches/plant as well as oil percentage in herb and leaves and N, K and B content in the herb. It increased herb and leaves fresh and dry weight/plant, oil yield of herb and leaves/plant as well as total carbohydrates, chlorophylls (a, b and total), carotenoids, P, Zn and Mo contents in the herb. Treating the plants with B at 50 ppm increased the vegetative growth, leaves and herb oil % and oil yield/plant, chlorophylls a, b and total, carotenoids, total carbohydrates content, N, Zn, B and Mo in the herb. Using B at 25 ppm led to an increase in the vegetative growth, oil% and yield in leaves and herb/plant, chlorophylls a, b and total, carotenoids, total carbohydrates content, Zn, B and Mo in the herb. However, it decreased P% in both seasons, compared to control plants.
Supplying the plants with Zn at 50 ppm resulted in the highest P% in the herb. It increased the vegetative growth as well as oil% and oil yield in herb and leaves/plant. It increased chlorophylls a, b and total, carotenoids, total carbohydrates content, N, P, Zn, B and Mo in the herb, compared to control plants. Application of Zn at 25 ppm resulted in an increase in plant height, oil% in the leaves, oil yield in leaves and herb/plant, total carbohydrates, chlorophylls a, b and total, K%, Zn, B and Mo content in the herb. However, it decreased herb and leaves fresh and dry weight/plant in comparison with untreated plants. Application of Zn at 100 ppm led to an increment in number of branches/plant, total carbohydrates, chlorophylls (a, b and total), carotenoids, N, Zn and B contents. While, it decreased plant height, leaves and herb fresh and dry weight/plant, oil% in leaves, oil yield of leaves and herb/plant and P % compared to control plants. Application of Mo at 10 ppm led to the greatest fresh and dry weights of leaves and herb/plant as well as oil yield of herb and leaves/plant, also total carbohydrates content in the herb. It increased plant height, number of branches/plant, oil percentage in both herb and leaves, N, K, Zn, B and Mo in the herb, chlorophylls (a, b and total), carotenoids content. It decreased P content in the herb, compared to untreated plants.
Spraying the plants with Mo at 5 ppm caused an increase in plant height, leaves and herb fresh and dry weights/plant, as well as oil% and yield of leaves and herb/plant, chlorophylls (a, b and total), carotenoids, Zn and B contents. However, P and K% in both seasons were decreased compared with control plants. Treating the plants with Mo at 20 ppm decreased all vegetative characteristics and the chemical determinations, except chlorophylls (a, b and total), carotenoids, Zn, B, and Mo contents which were increased compared to untreated plants.