Abstract:
Effects of gamma irradiation on thrips disinfestion and physiological changes ofDendrobium Sonia 'Bom#17' were studied. In the first experiment, effects of gamma irradiationat 0, 1 .O, 1.5 and 2.0 kGy on thrip disinfestation and tissue were examined. At doses of 2.0 and1.5 kGy, all thrips were dead after 2 and 4 days of irradiation, respectively compared tountreated flowers in which thrips survived for 14 daysS. canning electron microscope (SEM)was used to examine the irradiated flower tissue. Flowers were most damaged by 2.0 kGyirradiation. In the second experiment, physiological changes of dendrobium after gammairradiation were studied. Gamnla irradiation had effect on water uptake, fresh weight change,respiration, ethylene production, reducing sugar and vase life but no effect on petal colourchange. Water uptake and fresh weight of flowers treated with 2.0 kGy were the lowest but thehighest of respiration rate, ethylene production and reducing sugar content were observed.These flowers had 5 days of vase life and more flower-drop and failure of buds to opencompared to control flowers (13 days of vase life). In the third experiment, the relationshipsbctwcen gainma irradiation (0, 1.0 and 2.0 kGy) and added sucrose (4, 10 and 15% wlv) wereexainined. Gamma irradiation and sucrose concentration had no effect on water uptake, petalcolour change and reducing sugar content in buds and flowers. These treatments, however,affected respiration rates and ethylene production. At dose 1.0 kGy and 15% sucrose, the lowestrate of respiration and ethylene production were observed. Flowers treated with 1.0 kGy and 4%sucrose caused increase in fresh weight. Non-irradiated flowers treated with 4, 10 and 15%sucrose had longer vase life (17 days) while, 2.0 kGy and 10 and 15% sucrose had the shortestvase life (4 days) with more flower drops and failure of buds to open.