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Diploidy, Polyploidy, and Winter Hardiness Relationships in the Flowering Plants

Wray M. Bowden
American Journal of Botany
Vol. 27, No. 6 (Jun., 1940), pp. 357-371
Stable URL: http://www.jstor.org/stable/2436450
Page Count: 15
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Diploidy, Polyploidy, and Winter Hardiness Relationships in the Flowering Plants
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Abstract

A problem involving the relationships between chromosome number and the degree of winter hardiness in the higher plants is outlined. A scale of relative degree of winter hardiness was constructed in order to compare the resistance to cold of related species belonging to families ranging from the temperate zone to the tropics. The data so far obtained have been arranged in an extensive table, and show the author's chromosome number determinations of 100 species and varieties of angiosperms, with a comparison of counts already reported in related species. In most cases the differences in the degree of winter hardiness of related species are not correlated with chromosome number differences. A wide range of variation in degree of winter hardiness was found within the diploid species of many genera, and several hardy species which are the northernmost representatives of tropical families proved to be diploids. In numerous cases, the same chromosome number was found in hardy and non-hardy species of closely related genera belonging to tropical families. Tetraploid species are either hardier, less hardy, or of the same degree of hardiness as compared with related diploid species. The whole range of hardiness has been demonstrated within the tetraploid species of a genus. In other genera striking differences in the degree of hardiness were found within both diploid and tetraploid groups of species. These data indicate that, in nature, genic mutation and inter- and intra-specific hybridization have been more important processes than chromosome doubling. The data do not support the theory that polyploids are usually hardier than diploids and are therefore better adapted to climatically unfavorable regions.

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