RADIOSENSITIVITY OF ALBIZIA PROCERA TO ACUTE AND FRACTIONATED GAMMA IRRADIATION AT TWO MOISTURE LEVELS

Radiosensitivity of Albizia procera was calculated by exposing the seeds to acute and fractionated doses (0, 200, 400, 800, 1200 and 1600 Gy) of gamma rays at two moisture levels (6.5% and 48%). ED50/20 (effective dose) was estimated for seed germination, survival, growth and biomass of seedlings. Chromosomal aberrations were also scored at mitotic anaphase. The number of abnormal cells increased with the increasing doses of gamma rays. Presoaked seeds were more sensitive to gamma rays than those air-dried. ED50/20 doses of dry seeds under acute irradiation were 540 Gy and 770 Gy for shoot and root lengths respectively. Corresponding values for presoaked seeds were 135 Gy and 140 Gy respectively. The fractionated mode of irradiation showed comparatively more reductions in values of different parameters than acute irradiation for both dry and presoaked seeds of Albizia procera. This information could be of significance in further planning mutation breeding strategies and changing the spectrum of induced mutations by altering the mode of irradiation and moisture level of seeds. Radiosensitivi Albizia procera dikira dengan mendedahkan biji benih kepada dos akut dan pecahan (0, 200, 400, 800, 1200 and 1600 Gy) sinar gamma pada dua aras lembapan (6.5% dan 48%). ED50/20 (dos berkesan) ditaksirkan bagi percambahan biji benih, kemandirian, pertumbuhan dan biojisim anak benih. Aberasi kromosom juga dicatatkan pada peringkat anafasa mitosis. Bilangan sel abnormal bertambah dengan bertambah-nya dos sinar gamma. Biji benih yang diprarendam lebih sensitif kepada sinar gamma daripada biji benih yang dikering udara. Dos ED50/20 anak benih kering di bawah sinar akut ialah 540 Gy dengan 770 Gy bagi panjang pucuk dan panjang akar. Nilai sepadan bagi biji benih yang diprarendam masing-masing ialah 135 Gy dan 140 Gy. Sinaran dengan mod pecahan menunjukkan lebih pengurangan dalam nilai perameter berlainan berbanding dengan sinaran akut bagi biji benih Albizia procera yang kering dan yang diprarendam. Maklumat berikut boleh mempunyai makna dalam cadangan strategi pembiakan mutasi dan mengubah spektrum mutasi teraruh dengan mengubah mod sinaran dan aras lembapan bagi biji benih.