The effects on papaw (Carica papaya L.) shoot growth of the carbohydra
tes sucrose, fructose, glucose and ribose singly and combined, were co
mpared at a range of concentrations, in both autoclaved and filtered m
edia. Fructose (10 g L(-1)), when autoclaved together with other media
components, consistently promoted growth of shoots from buds on nodal
sections or buds excised with a wedge of stem tissue. This enhancemen
t was seen if the fructose was used singly or in combination with 10 g
L(-1) sucrose. By contrast, autoclaved media containing fructose redu
ced growth of small axillary bud explants. Decreasing the pH of fructo
se solution from 5.8 to 4.4 before autoclaving enhanced growth of buds
from nodal sections. Other sugars in the D-ketose group inhibited pap
aw shoot growth totally when autoclaved with other media components. A
radish cotyledon bioassay of solutions of fructose autoclaved singly
or with NH4NO3 (20 mM) showed no evidence of cytokinin effects.