SCHIZOGENOUS SECRETORY CAVITIES OF CITRUS-LIMON (L.) BURM. F AND A REEVALUATION OF THE LYSIGENOUS GLAND CONCEPT

The lysigenous appearance of Citrus limon (L.) Burm. f. secretory cavi ties is the result of fixation artifacts. The glandular epithelial cel ls of lemon glands undergo rapid destructive swelling when immersed in commonly used fixatives. The swelling is most evident with mature gla nds, causing a false impression that the epithelial cells undergo auto lysis as they complete their development. Epithelial cells of secretor y cavities sliced open during tissue preparation show more extensive s welling than those left intact during fixation, indicating a possible cause for inconsistencies among reports of Citrus gland development. A queous primary fixation of intact secretory cavities results in suffic ient epithelial cell swelling to give a false impression of precocious senescence; osmium vapor-fixed glandular cells show less swelling, co ntain intact organelles, and appear living at gland maturity. Although the concept of lysigeny is very old, recent evidence for lysigeny is based on investigations that used standard aqueous fixatives. Since fi xation requirements for glands from other species of plants could be s imilar to those for Citrus glands, we suggest that lysigeny, in genera l, could be a false category of gland development, representing misint erpretation of artifacts.