M.A. Thesis:

Effect of multi-walled carbon nanotubes on shoot regeneration and in vitro rooting of stevia (Stevia Rebaudiana L.)

To evaluate the effect of carbon nanotubes on in vitro shoot regeneration and rooting of stevia plant, two separate factorial experiments in a completely randomized design with 4 replications were done in biotechnology laboratory of Islamic Azad University of Sabzevar. At the first, effect of application of carbon nanotubes and BAP concentration on shoot regeneration from stem single node cuttings was evaluated. Experimental factors consisted of multiwalled carbon nanotubes at three levels (0, 10 and 50 ?g/ml) and two concentrations of BAP (1 and 1.5 mg l-1). In this experiment, the MS medium was used as basal medium. After selection of the best medium composition for shoot regeneration, effect of carbon nanotubes application (0, 10 and 50 ?g/ml) and IBA concentrations (0.5, 1 and 1.5 mg/l) on in vitro rooting of shoots were studied. The results showed that carbon nanotubes concentrations had significant effect on all shoot regeneration characteristics. Application of carbon nanotubes in the culture medium decreased the percentage of shoot regeneration, that this reduction was more in 50 ?g/ml concentration. However, the concentration of 10 ?g/ml of carbon nanotubes improved shoots number and length compared with non-use of carbon nanotubes. The number and length of shoots decreased at the concentration of 50 ?g/ml of carbon nanotubes compared with control and 10 ?g/ml carbon nanotubes concentration. BAP concentration had no significant effect on the percentage of shoot regeneration and the number of shoots, but its effect on shoot length was significant. The longest shoot was obtained at a 1 mg l-1 BAP concentration.. The use of carbon nanotubes in the medium increased the rooting percentage and the number of roots per shoot. The highest rooting percentage and number of roots were observed at 10 and 50 ?g/ml carbon nanotubes concentrations, respectively. Increasing the concentration of IBA, increased the rooting percentage of shoots, so that the maximum percentage of roots was recorded at 1.5 mg/l IBA concentration. IBA concentration had no significant effect on root number per shoot

Keywords: Stevia, shoots, rooting, carbon nanotubes, cytokinin