Induced colchiploidy in Nicandra physaloides.

Abstract

Using colchicine (0.2%) as the polyploidizing agent colchiploid Nicandra physaloides was raised. The induced autoploids were evaluated on such parameters, as morphology, cytology, pollen and plant sterility. The colchicine was given either by soaking the seeds in the solution or by wetting cotton plugs with the solution placed on apical meristems. Treated plants initially showed impaired growth which later improved and ultimately showed gigantism. The pollen grains and stomata, however, were consistently bigger in size.Despite the presence of multiple homologues, the autotetraploids tended to avoid multivalent formation and produced exclusively bivalents which appeared to help normal disjunction of chromosomes at anaphase. Yet, abnormalities appeared due to the mutagenic effect of the chemical; the consequences of these being in-creased pollen sterility which lowered plant fertility. From the seeds of C1, C2 plants could be generated but majority of them showed reversion to the diploid state. The gigas characters of C1 also tended to lessen in C2 generation. Con-comitantly a general improvement in pollen and plant fertility was noticed in this generation.