Abstract
A number of diploid and polyploid species of wheat have been analysed for the sensitivity of their chromosomes to conditions of high temperature. A comparative estimate of deoxyribonucleic acid in the root-tip cells of different species has also been made by the autoradiographic technique. The diploid and hexaploid species differed greatly in temperature sensitivity of their chromosomes. The diploid, tetraploid and hexaploid species contained an increased amount of DNA in that order but the increase was not proportional to the chromosome number in these species. No simple correlation was found to exist between the amount of DNA in the cells of different species and the temperature sensitivity of their chromosomes.
