IRRADIATION DOSE AND EFFECT ON GERMINATION AND GROWTH OF DESERT SHRUB NITRARIA TANGUTORUM BOBR. WITH TWO GAMMA IRRADIATION MODES

Abstract

The seeds of Nitraria tangutorum were exposed to different doses of gamma radiation from 60Co gamma rays based on the two irradiation modes of without dose rate and with dose rate of 25Gy/hr. The effects of different irradiation modes and irradiation dose on the seed germination rate, emerged seedling rate and phenotypic characters of seedling have been studied. The semi-lethal dose and critical dose were determined for different irradiation mode. It has been found that there were the differences of irradiation effects between the two irradiation modes. Promotion effect on the seed germination rate, emerged seedling rate, seedling height and ground diameter in lower dose treatment were observed, while inhibition in higher dose. As compared to control, the irradiation effects on the seed germination rate and seedling height and ground diameter present the very remarkable differences at above 1500Gy dose without dose rate mode, while above 2400Gy with dose rate mode. The negative relativity exists between the relative emerged seedling rate and irradiation dose, the emerged seedling rate decreased with increasing dose. The semi-lethal dose based on the emerged seedling rate was 985Gy and 1363Gy for the irradiation without dose rate and with 25Gy/hr dose rate, respectively. The Appropriate 60Co gamma irradiation dose for the Nitraria tangutorum seeds was ranging from 950 Gy to 1500Gy without dose rate irradiation mode, while 1300Gy to 2400Gy with 25Gy/hr dose rate mode.