Biology and Agriculture Division, Bhabha Atomic Research Centre, Bombay-85
*Part of this work was carried out as research contract No. 497/R2/RB with the International Atomic Energy Agency.
Seeds of diploid Corchorus slitorius cv JRO 632 and a neutron induced, true breeding and fertile autotetraploid were irradiated with several doses of gamma rays and fast and thermal neutrons. The induced autotetraploid was found to be more sensitive than the diploid to all the three types of radiations. The RBE of fast neutrons for seedling height reduction was also low for the tetraploid. From the D50 doses of gamma rays and thermal neutrons for seedling height reduction, it was found that 1 rad of gamma rays produced the same effect as 2.71 × 109 nth/cm2 in diploid and 6.09 × l08 nth/cm2 in the tetraploid. Equivalent doses of thermal neutrons were calculated from these values for the gamma ray doses and the mutation rates when plotted against these doses showed that thermal neutrons are 2.5 to 3.5 times more efficient than gamma rays for the corresponding biological damage as measured by seedling height reduction.
