Effects of Freezing Time on Observation of Chromosomes in Exacum ritigalensis (Binara/Ginihiriya)

Abstract

In this study, freezing time at 0.01% colchicine was practiced to observe chromosome from Exacum ritigalensis. Fifty, two weeks old seedlings of E. ritigalensis were randomly selected and all actively growing root tips about 10mm in length were excised from each plantlets. These root tips were washed with tap water to remove the residues of the medium. Root tips treated with 0.01% colchicine solution were kept at room temperature for either two hours (control) or at at 4°C for either 1,1.5, 2 and 2.5hrs. The experiment followed a completely randomized design with ten replicates were used for each treatment Treated root tips were placed on glass slide and stained with one drop of carbolfuchsin solution and were observed for chromosomes under a microscope (Axio Lab A l), and photos were taken with the associated apparatus. Then they were ranked using a scale 0,1,2, 3, and 4 from 0 to 4 (very poor, poor, satisfactory, good and very good), according to the viisibility and for clearness of chromosomes in cells; Statistical analysis was performed by Wilcoxon sign rank test using SPSS statistics package (version 20). It was observed that Exacum ritigalensis diploid plants with 28 chromosomes and also results revealed that two hours freezing at 4°C gave the best picture of chromosome than other treatments.