Polyploids are More Variable than their Original Diploids

Abstract

STUDYING the modification of a large number of experimentally produced polyploid plants of various species and families (Solanaceæ, Gramineæ, Compositæ, etc.) within the single plants and in the polyploid lines in respect to the modification of their diploid forms, when the plants grew in equal environmental conditions, I found the following regularities. Cell dimensions showed in the majority of the cases studied a greater modification in the tetraploid than in the diploid plants. Cell dimensions of the experimentally produced octoploids were more variable than the cell dimensions of tetraploid and diploid forms. The numbers of chloroplasts per pair of stomatal cells were more variable in the tetraploids than in the diploids and much more variable in the octoploids than in the tetraploids and diploids. Counting, for example, the chloroplasts¹ in 100 pairs of stomatal cells of each form of Nicotiana alata—diploid, tetraploid and octoploid, the following values for the standard deviations were respectively found: σ_2n = 1·81, σ_4n = 4·70, and σ_8n = 7·03. (It was found that polyploidy does not affect the size of the chloroplasts^{1 2}. It also does not significantly affect the variability of the chloroplast diameter.) The modification of the cell dimensions decreases somewhat gradually in the subsequent polyploid generations, that is, it decreases with the increase of the polyploid generations. But in the cases studied tetraploids still had more variable cell dimensions in the fifth generation than the corresponding diploids.