Similarly, the appearance and behaviour of chromosomes at preleptotene decondensation is indistinguishable from that normally seen at mitotic telophase. The appearance and behaviour of chromosomes at preleptotene condensation stage is the same as that displayed by chromosomes at mitotic prophase. The nature and possible significance of preleptotene chromosome condensation and decondensation are discussed. Thereafter chromosomes underwent decondensation and elongation and eventually passed into leptotene without first entering any other stage. At this stage the appearance of the chromosomes was indistinguishable from that of late prophase or prometaphase chromosomes at mitosis. At maximum chromosome contraction the diploid chromosome number (2n = 24) could often be counted, but no evidence of association of chromosomes was seen. All the p.m.cs within an anther loculus underwent preleptotene chromosome condensation stage with a degree of synchrony not less than that found at early first meiotic prophase. 'Black Beauty' p.m.cs entered preleptotene chromosome condensation stage from G2 of premeiotic interphase having completed DNA synthesis.

A brief illustrated description is given of the appearance of p.m.cs at various stages of preleptotene chromosome condensation in both methylene blue stained anther sections, and in Feulgen stained anther squashes. chromosomes during preleptotene condensation and decondensation was essentially the same as that described by Walters (1970, 1972) for the corresponding stages in Lilium longiflorum cv. Moreover, the preleptotene condensation and decondensation stage was apparently shorter in e.m.cs (about 0.7 days) than in p.m.cs. However, the maximum degree of chromosome contraction at the preleptotene condensation stage was much greater in p.m.cs than in e.m.cs. Preleptotene chromosome condensation and contraction also occurred in embryo sac mother cells (e.m.cs) of 'Black Beauty'. The duration of this period was estimated to be about 1.16 days in pollen mother cells (p.m.cs) of plants grown at 20 degrees C.

A period of chromosome condensation followed by decondensation occurs between premeiotic interphase and leptotene in Lilium hybrid cv.

Vickers m41 photoplan