Abstract:
Banana shoots were cultured on the medium containing either one of the three gelling agents agar, gelrite and gellan gum for 13 weeks. The concentrations of the nutrient elements especially macro-elements, were higher in gelrite than in agar and gellan gum. Each of the three gelling agents had an optimal concentration for plant growth, but as a whole, shoot growth and multiplication was higher on the medium solidified with 0.9 g L-1 gelrite as compared with those on the medium solidified with 4-8 g L-1 agar or 2-6 g L-1 gellan gum. This may be attributed to the availability and uptake of water and mineral nutrients. Most of the shoots cultured on 0.7 g L-1 gelrite or 4 g L-1 agar and on the liquid medium showed poor growth and multiplication due to vitrification. The higher concentrations of gellan gum (6 g L-1) and agar (8 g L-1) did not support shoot growth and this was explained by reduced water and mineral salt uptake. At the concentration of each gelling agent that gave the best shoot growth and proliferation (gelrite 0.9, agar 6 and gellan gum 2 g L-1) the water potential of the medium was about -0.5 MPa and the medium with a water potential of about -0.6 MPa did not support plant growth. We concluded that the growth of banana plants in vitro was affected by the type and concentration of gelling agent mainly due to the difference in the physical properties of the medium
