Portal de Periódicos da CAPES

Biosystematics of Sisymbrium Irio Complex

1958; University of Florence; Volume: 11; Issue: 2 Linguagem: Inglês

10.1080/00087114.1958.10797039

2165-5391

T. N. Khoshoo,

Chromosomal and Genetic Variations

SUMMARY AND CONCLUSIONSA comparison of habitat preferences, morphological characters and pollen and seed fertilities of the various races within the Sisymbrium irio complex has been made.Pending cytological evidence, it could be concluded from the above comparisons that the various races have not arisen due to the autoploidy of the genome of the diploid. Had it been so, then there would be uniform differences of only quantitative nature among the five races. That these races have genomes completely different from one another, is also ruled out since there do exist some basic resemblances between all of them. However, the complex constitutes a single phylogenetic unit in which the different characters are shared by various races to varying extent. This has caused « reticulation » in relationship. It is clear that morphologically the diploid, triploid and hexaploid form a single group and the tetraploid and octoploid form the other group. There are, however, some differences among the members of each group. Furthermore, some tentative conclusions emerge with regard to the nature of ploidy in each case. The triploid though showing a close resemblance to diploid is not its autoploid. The tetraploid shows only a far-fetched resemblance to the diploid and the former is not an autoploid from the diploid. The hexaploid is not a complete autoploid of the diploid since like the triploid, it has features which are not found in the diploid. The octoploid is perhaps an autoploid from the tetraploid, because it shows mostly quantitative differences from the tetraploid.The four branching patterns within the complex appear to have an adaptive value. These differ in the extent of vegetative and reproductive portions. The races which occupy favourable habitats (diploid, caulis and hexaploid) have both systems equally well-developed, while subcaulis which occupies dry habitats shows reduction in vegetative portion of the mainstem. In this case the plant starts flowering almost directly after rosette stage since the selection would favour a quick-flowering and quick-maturing type. The acaulis type occurs in moist grazed ground and is acaulescent since a low- growing form would be at a selective advantage.