The Nature of Differential Reactivity in the Heterochromatin of Trillium and Paris spp

Abstract

1. The degree of differentiation attained after chilling varies from one H-segment to another in Trillium, both between and within the species. These can be grouped into four degrees:
1° Slight (e.g. T. stylosum)
2° Moderate (e.g. most Trillium segments)
3° HIGH (e.g. Paris polyphylla)
4° Extreme (e.g. T. undulatum and Japanese species)
2. H-segments lose their differential appearance when chilled chromosomes are blocked at metaphase and returned to normal temperatures. This would seem to be due to a synthesis of DNA by H-segments, which are regarded as being retained in an early prophase condition. There is evidence that all H-segments from metaphase to late anaphase are capable of such synthesis.
3. Differential reactivity in polyploid cells and plants is identical with that in its diploid counter-part.
4. Chemical treatment of Trillium chromosomes has failed to reveal H-segments. This might be due to the chemical treatments being nonspecific for heterochromatin. All the chemical methods suggested in the literature seem to be variable and therefore unreliable in their results.