Karyotype Analysis in Gymnospermae, I

Abstract

The karyotype analysis of Ginkgo biloba L. has been studied in the mitotic cells of young leaf meristems. The basic number (b) is twelve. A haploid chromosome complement in both sexes contains two submedian and ten subterminal chromosomes, of which the longest is submedian and has a trabant, and the eighth is subterminal and trabanted. The. chromosome with tandem trabants is occasionally found. The karyotype formula follows: K(2n)=24(2b)=2^tA^sm+2B^st+2C^sm+8D^st+2^tE^st+8F^st where t, sm, and st represent trabant-, submedian-, and subterminal chromosomes, respectively. Sticky chromosome bridges in ana- and telophases in mitotic cells have been met with in the young leaf meristem not infrequently. This irregularity was frequent in the young leaf shoots sprouted early in April, and decreased as the date elapsed and diminished at the end of May. It is suggested that these irregularities caused by the special physiological condition are probably due to cellular inclusions-certain organic substances extractable by water.