Pollen Abortion in Chromosomal Types of Datura

Abstract

Data on the percentages of aborted pollen grains in various unbalanced and balanced chromosomal types of Datura are given. In each series pollen of 4 flowers from each of 3-4 plants of each type was studied, and the percentages of aborted grains are based upon a count of at least 500 grains from each flower. A large part, at least, of pollen abortion in Datura is due to abnormalities in chromosome constitution. In the balanced series the averaged percentages of abortive pollen grains were: haploid, 87.95; diploid, 1.16; triploid, 43.61; tetraploid, 5.16. In the pollen of haploids apparently all grains with less than the complete haploid chromosome complement abort, and the 12% of normal grains arise by non-reduction of the 1 n mother cells. Non-disjunction and detachment may account for the 1-2% abortion in normals, and also for the 5% in tetraploids, where these irregularities are more frequent. The Primary (2n + l) types show more abortion than normals, with 2.21-10.16%. Apparently, the unbalance of the extra chromosome renders the pollen grains less viable, the proportions depending upon which chromosome is extra. In all cases the Secondaries (2n+2/2) with the extra doubled-half-chromosome have more aborted grains than their Primaries, showing 3.50-20.80% pollen abortion; and here the unbalance is also greater. The 43% of pollen abortion in triploids is probably chiefly due to the unbalance in grains with more than 1 extra chromosome. Size and condition of the mature pollen grains may often indicate the chromosomal group to which the plant belongs.