A STUDY BY CRYOSCANNING ELECTRON-MICROSCOPY OF THE INITIATION AND EARLY DEVELOPMENT OF AN INFLORESCENCE IN GLASSHOUSE CELERY (APIUM-GRAVEOLENS L VAR DULCE (MILLER) PERS) GROWN UNDER INDUCTIVE CONDITIONS

The morphology of flower initiation and early development in glasshous e celery (Apium graveolens L. var. dulce (Miller) Pers.) cv. Celebrity was studied by means of apical dissections and cryo-scanning electron microscopy. Easily recognisable morphological features were used to d efine seven stages in the early development of the inflorescence. A hi ghly significant linear regression was established between the logarit hm of the apical diameter (measured diametrically across the apical do me between the two most recently initiated leaf or inflorescence primo rdia) and these discrete floral stages. There was no strong evidence t hat either the origin or the slope of the regression varied with diffe rent combinations of temperature (viz. 10 degrees C or 14 degrees C) a nd daylength (viz. natural, short or long) which were conducive for th e initiation and development of an inflorescence. It is suggested that both apical diameter and floral stage may be used as parameters for a ssessing the influence of environmental factors such as temperature an d daylength on the floral development of glasshouse celery.