The effects of polyploidy on meiotic duration and pollen development in cereal anthers

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Abstract
The anther is useful for the study of development because it provides comparisons between mitotic and meiotic divisions; between nuclear behaviour during the sporophyte and gametophyte stages; and between cell cycles and divisions involving cells with different nuclear DNA contents. The duration of the period from the immediately premeiotic mitosis until the start of leptotene at 20 degrees C was estimated to be about 48 h in hexaploid Chinese Spring wheat (Triticum aestivum), and about 42 h in diploid Petkus Spring rye (Secale cereale). Comparisons of the durations of meiosis and of pollen maturation in wheat, in rye and in Triticale genotypes showed that in all three the durations of these stages of development decreased as ploidy level increased. Within each ploidy level, genotypes with higher nuclear DNA content had longer meiotic durations. Differences in both meiotic duration and pollen maturation resulted from proportional differences in the duration of all component stages. These results obtained from comparisons of a closely related group of species in the Gramineae are similar to the results obtained previously (Bennett 1971) from comparisons of plant species taken from widely different families. Data in animals showing positive linear relationship between meiotic duration and the duration of spermatogenesis are collected. Possible causes of the faster rates of development during meiosis and pollen maturation in polyploid cereal species, and of the constant proportions between the durations of all their constituent stages, are discussed.
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