Effects of Various Carbon Sources and Their Combinations onin vitroGrowth and Photosynthesis of Banana Plantlets

The effects of various carbon sources, sucrose, glucose and fructose alone or in combination on the in vitro growth of banana plantlets were studied. Banana plants were cultured on the media supplemented with these carbon sources at 0.08 M for 13 weeks. The water potential of the medium was the highest in the medium supplemented with sucrose + glucose (-0.3 MPa), and was significantly lower in the medium supplemented with fructose alone or in combination with other carbon sources (-0.7 to -1.0 MPa) than in the other media. The leaf water potential was also the highest in the plants cultured on the medium supplemented with sucrose + glucose, and lowest in the plants cultured on that with fructose. The leaf water potential of plants cultured on sucrose + glucose, sucrose and glucose correlated well with their growth and photosynthetic activity, but the correlation was not observed in the plants cultured on fructose alone or in combination with other carbon sources. Plants cultured on fructose had a lower chlorophyll content (400 ptg dm-2) and lower photosynthetic rate (3 μmol02 m-2 s-1) than those cultured on sucrose + glucose (15,950 μgdm-2 for chlorophyll and 8.5 μmol02 m-2 s-1 for photosynthesis), and these differences were statistically significant. Both chlorophyll content and photosynthetic oxygen evolution were the highest in the plants cultured on sucrose + glucose, and the superior growth of plants on this medium was attributed to their high photosynthetic efficiency.