Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Ornamental Horticulture

The present study was conducted during two successive seasons of 2015 and 2016 in the Ornamental Horticulture Deprtment, Faculty of Agriculture, Cairo University and Experimental Farm of Medicinal and Aromatic Plant Research Department, Horticulture Research Institute, Agricultural Research Center, Dokki, Giza to study the effect of different saline water concentrations (tap water, 1500 and 3000 ppm), seaweed extract at concentrations of 0, 0.25, 0.5 and 1 g/l, and salicylic acid at concentrations of 0, 150, 300 and 450 ppm on Plectrunthus amboinicus plant. The most important results can be summarized as follows: Tap water treatment increased plant height, number of branches, leaves: stems fresh weight ratio, leaf area, fresh and dry weights/plant, essential oil yield/plant, pigments contents, total carbohydrates, N,P and K % in the two cuts of both seasons.Whereas salinity at 3000 ppm increased essential oil percentage, {u01A4}- cymene, Ý- caryophyllene and Ü- humulene contents in the oil, Na and proline contents. Seaweed extract or salicylic acid at different concentrations significantly increased plant height, number of branches, leaves: stems fresh weight ratio, leaf area, fresh and dry weights/plant, essential oil percentage, essential oil yield/ plant, pigments contents, total carbohydrates, N, P and K %, while decreased Na and proline contents in the two cuts of both seasons. Seaweed extract at 1 g/l or salicylic acid at (450 ppm) were the most effective treatments in this respect. Control treatment (tap water) combined with seaweed extract at 1 g/l or salicylic acid at 450 ppm gave the highest values of most charecteristics compared with salinity treatments without spraying seaweed extract or salicylic acid at different concentrations

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