Surface Changes on Fresh Carnation Shoot Apices During Scanning Electron Microscopy

The general morphology of fresh intact shoot apices of carnation,Dianthus caryophyllus L. cv. Improved White Sim was studiedwith a scanning microscope. The changes in the surface withtime under the electron beam were: (1) individual cells beingvisible, (2) a smooth apex and (3) wrinkling until the specimenbecame unsatisfactory for study. As indicated by time coursestudies, the initial individual cell observations representthe true features of the intact apex. The observation of a smoothapex was related to a ballooning of the surface layer resultingfrom water vaporization. Incisions in the apex to prevent pressurebuild-up under the surface layer revealed the smooth characteristicof the apex surface was due to lifting of the cuticle from underlyingcells. Areas adjacent to a micropuncture in the apical domedid not exhibit ballooning.