MORPHOLOGICAL FACTORS OF THE CENTRAL WHORL LEAF ASSOCIATED WITH LEAF SURFACE WETNESS AND RESISTANCE IN SORGHUM TO SHOOT FLY, ATHERIGONA-SOCCATA

Earlier studies showed that leaf surface water on the central whorl le af of sorghum seedlings is associated with resistance to shoot fly. In this study, the results of an experiment to determine if leaf surface wetness (LSW) originates from atmospheric condensation or from the pl ant are described. Morphological structures: trichomes, stomata, leaf cuticle and quantity of surface wax of the central whorl leaf were als o examined for their role in LSW production. The results suggest that LSW of the central whorl leaf originates from the plant and is not due to condensation of atmospheric moisture. The presence of trichomes wa s indirectly associated with LSW and resistance to shoot fly but stoma tal density was not associated with LSW production. The amount of wax extracted per 100 mg of fresh weight varied significantly between geno types and seedling age. It was more in susceptible than in resistant g enotypes; however, cuticular thickness was not associated with resista nce. It is suggested that LSW could be the result of some form of cuti cular movement of water to the leaf surface.