In vitro polyploidy induction by colchicine in Poinssetia

In this experiment the mitotic inhibitore colchicine was evaluated for tetraploid induction of Poinssetia (Euphorbia pulcherrima var. pendora red). The regenerated shoot tip explants were induced with 0.00, 0.02, 0.05, 0.1, 0.2, 0.5 and 1% ( w/v) concentrations of colchicine for 6, 12 and 20 hours, respectively. The most effective treatment was 0.1% colchicine for 12 hours with polyploidy induction rate of 33.0%. The stomata size of tetraploids (18.23× 5.37μm) was significantly larger than that of diploids (12.1× 4.31 μm) but the stomata density of tetraploids (14.89 mm2 ) was significantly lower than that of diploids (23.10 mm2). Compared with diploids, tetraploids had thicker, wider, shorter, rougher and deeper-colorful leaves, fewer roots, shorter shoots and slower growth. Control plants that were considered as diploid  plants showed 2n = 2x =28 chromosome number whereas treated plants with 1 w/v % and 6 hours colchicine, showed doubled the number of chromosomes (2n = 4x = 56) who were identified as tetraploid plants. The leaf and the stoma characteristics and chromosome counting could be regarded as helpful indexes to identify colchicine-induced tetraploids in Poinssetia.