IRADIASI AKUT DENGAN SINAR GAMMA PADA PROTOKORM ANGGREK Dendrobium macrophyllum A. Richard DAN Dendrobium undulatum M. A. Clem & D. L. Jones

Increasing genetic variation in plants can be done by irradiation technique. The purpose of this study was to improve genetic variation in Dendrobium macrophyllum and D. undulatum orchids by gamma irradiation to obtain superior seeds. Accute Irradiation treatment was perfomed using orchid protocorms. Irradiation doses given: 0, 10, 20, and 25 Gy. The observed parameters were the number of explants, shoots, dead shoots, and leaves at five months after treatment (MAT) and number of roots in seven MAT. Calculation of Lethal Dosage (LD) 20 and 50 was carried out on three MAT. The results of Curve Expert analysis showed that different levels of radiosensitivity in D. macrophyllum were more sensitive than D. undulatum . D. macrophyllum showed LD 20 at an irradiation dose of 13,98 Gy, LD 50 at an irradiation dose 48,42 Gy, while D. undulatum experienced LD 20 at an irradiation dose of 195,67 Gy, LD 50 at an irradiation dose of 490,67 Gy. Acute irradiation effects were seen in protocorm D. macrophyllum at seven MAT in the presence of inhibition at 10 Gy irradiation doses, which was a decrease in the number of shoot of 2,66, decrease in leaf number 18,84 and decrease in root number 5,17 compared to control