EPICUTICULAR WAX OF THE FIRST LEAVES OF 2 BARLEY CULTIVARS STUDIED BYCRYO SCANNING ELECTRON-MICROSCOPY

Chemical fixation and critical point drying of plant tissue prior to s canning electron microscopy often degrades the outermost layer of the specimen, i.e. the epicuticular wax. Knowledge of the unaltered wax, i ncluding its morphology, is important because the wax constitutes the interface between the plant and its surroundings. Having worked previo usly with barley leaves (anatomy, infection biology of pathogens), we found it of interest to examine and describe the wax morphology on bar ley leaves and to determine whether or not there were differences betw een cultivars. Hence, the morphology of the epicuticular wax on the fi rst leaf of two spring barley cultivars has been studied by scanning e lectron microscopy following cryofixation. The wax on both cultivars c onsists chiefly of scales with a small proportion of rods and granules . There is little variation in wax morphology over each leaf side, and only minor differences between the abaxial and adaxial sides of the s ame leaf. Distinct differences are, however, observed between the two cultivars, especially regarding the thickness and the shape of the wax scales. The wax bodies cover the entire surface of a leaf except for pairs of trichomes and guard cells, and some scattered wax free areas. The morphology and distribution of wax are discussed in relation to s tudies made on barley leaves using different techniques. Also, the imp lications of wax morphology for disease resistance are briefly discuss ed.