Banded Polytene Chromosomes in the Legume Phaseolus vulgaris

Abstract

GIANT chromosomes have recently been found in different cells in the ovule of some Angiosperms^1–3. The homologues are not paired and they have a granular structure without distinct bands, thus differing from the characteristic salivary gland chromosomes of Chironomus or Drosophila. They are more comparable with the primary polytene chromosomes in the ovary of Calliphora^4,5, or the salivary gland chromosomes of Dasyneura⁶. In Phaseolus coccineus the single giant chromosomes could only be identified in the suspensor cell nuclei, because of the uniformity of euchromatic and heterochromatic regions^7–9. In the Diptera the appearance of distinct bands sometimes depends on a low breeding temperature^4,10–12, and so we have investigated the influence of temperature on the structure of giant chromosomes in the Angiosperm Phaseolus vulgaris, which is known to have giant chromosomes in the suspensor cell nuclei similar to those described for Phaseolus coccineus. The plants, however, are smaller, fast growing, and self pollinating, and therefore readily cultivated in phytotrons.