THE DURATION OF MEIOSIS IN DIPLOID AND AUTOTETRAPLOID BARLEY

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Abstract
The duration of meiosis and its constituent stages are given for diploid and autotetraploid Ymer barley grown at 20 °C in continuous light. In the diploid, the total meiotic time was about 39 ± 1 hr in both cultured anthers and on whole plants. In the tetraploid, the total meiotic time was about 31 ± 1 hr in cultured anthers. In both genotypes, each meiotic stage occupied about the same proportion of the total meiotic time as in other species.In unsampled anthers the tapetal nuclei divided synchronously while the pollen mother cells were at pachytene and each tapetal cell became binucleate. Normal development in the tapetum and archesporium was much more easily upset by sampling techniques during pachytene than at any other stage.The duration of meiosis in diploid Ymer agrees closely with our previous estimate for diploid Sultan barley. The shorter meiotic duration of the auto-tetraploid compared with that of the diploid is to be expected in the light of the decreased meiotic time of tetraploid Svalöf 4x rye compared wih diploid Petkus Spring rye (Bennett and Smith, 1972) and the interspecific comparisons of meiotic times made by Bennett (1971).The development timing differential between adjacent spikelets was much less during meiosis than at the primordial stage.Abnormal tetrads which occurred spontaneously at a low frequency in tetraploid Ymer are discussed. They were probably associated with spindle abnormalities.