An investigation on the activity of root xylem exudate of cucumber (cucumis sativus l. ) seedlings in various bioassays related to plant growth hormones

II SUMMARY Master Thesis AN INVESTIGATION ON THE ACTIVITY OF ROOT XYLEM EXUDATE OF CUCUMBER (Cucumis sativus L. ) SEEDLINGS IN VARIOUS BIOASSAYS RELATED TO PLANT GROWTH HORMONES Songül ÇANAKÇI Fırat University Graduate School of Natural and Applied Sciences Department of Biology 1994, Page : 41 6 days old Cucumis sativus L. seedlings were exposed to cigarette smoke in a closed system for 24 hours and later growth parameters were determined, Subsequent to smoke application, the seedlings were decapitated and root exudates obtained by collection was seperated from treated and untreated seedlings were seperated in to various fractions by solvent partitioning and chromatography. Using specific hormone bioassays, the activities of these fractions were determined. The basic water phase was assayed with radish cotyledone expansion method for cytokinins. The neutral-acidic ethyl acetat phase, on the other hand, was assayed with wheat coleoptile straight growth method for auxins and ABA, and with lettuce method for gibberellins. Our results showed that the stress caused by cigarette smoke application gave rise to an increase of ABA and to a decrease of cytokinin levels in root exudate along with growth inhibition in the seedlings. The.gibberellin activity could not be determined in the exudate due to the failure of the chromatography in the isolation of them in a certain Rf zone. KEY WORDS: Cigarette smoke, plant growth substances, seedling growth, inhibition, root exudate, bioassay.