Morphological and cytological studies of colchicine-induced tetraploids inTorenia fournieri lind

The present paper concerns a morphological and cytological comparison between the naturally occurring diploid and the colchicine induced tetraploid ofTorenia fournieri Lind.Treatment of growing points of young seedlings with 0.20% aqueous colchicine for 10 hours on two successive days was most effective in inducing tetraploidy. The induced tetraploids showed the usual gigas characters associated with autotetraploidy. There was a significant reduction in pollen fertility and seed setting of tetraploids as compared to their diploid progenitors.The chromosome numbers of the diploids and the induced tetraploids were determined as n=9 and n=18, respectively. The diploids showed normal meiosis whereas tetraploids were characterized by a high frequency of unequal distribution of chromosomes at anaphase. The induced tetraploids possessed larger flowers. The variability in flower size of the tetraploids offers a good scope for evolving a better horticultural variety of this species.