Effects of 6-(3-methyl-2-buten-1-ylamino)-purine and α-naphthaleneacetic acid on root formation and cytology of root tips and callus in tissue cultures of Allium cepa var. proliferum

Tissue cultures of Allium cepa var. proliferum grown in liquid medium were treated with a cytokinin, 6-(3-methyl-2-buten-1-ylamino)-purine (2 iP) and α-naphthaleneacetic acid (NAA) in different concentrations. The formation and elongation of roots were stimulated by 2 iP, the optimum concentration of which varied with the age of the cultures. The mixoploid root tips of the control series showed a high percentage of polyploidy, but with 2 iP in the medium the cells were essentially 100% diploid. A similar effect was seen in cells of callus tissue. The effects of NAA were similar to those of cytokinin in that the root tip cells showed increasing diploidy to nearly 100% at the optimum concentration of 5 mg/l. However, in the NAA-treated series root formation and elongation were less pronounced than in the 2 iP-treated series.