Studies in the Indian Scilleae

IV. The Cytology of triploid Urginea indica Kunth

Abstract

The existence of triploidy in Urginea indica, was suspected some years ago by the senior author. Triploids were now isolated from a heterogenous wild population. The diploid and the triploid have been studied on the basis of comparative morphology. The existence of a positive correlation between gigas characters and chromosome number has been confirmed.
A comparative study of the rate of growth of the floral scape has been made of the diploid and the triploid, and it was revealed that it is higher in the triploid than in the diploid. No discrepency was observed in respect of the time of flowering of the triploid and diploid. Both flower almost simultaneously. This is not in consonance with a few observed cases of retarded growth, exhibited by polyploid forms. The question is raised whether conclusions arrived at on the basis of the slower growth rate etc., of polyploids are to be accepted as universally true in the face of data, such as are presented in this paper and a few others, where there is no evidence for a slower rate of growth in the polyploids as compared with the diploid forms.
Meiosis in the triploid is described in detail. All the irregularities are described, like the elimination of chromosomes, formation of micronuclei and microcells, iameiosis, formation of restitution nucleus etc. The occurrence of unequal nuclei in pollen mother cells and their independent behaviour leading to the formation of tetrads of unequal size are also described. The possible origin of the triploid is also discussed in the light of the data on hand.