French bean (Phaseolus vulgaris L.) cotyledons lost most of their reserve substances during several early days of germination and turned green. In cotyledon mesophyll cells of one-week-old seedlings, plastids were represented predominantly by amyloplasts (starch grains) and chloroamyloplasts, and the cells appeared to be metabolically highly active. Cell heterogeneity associated with distance of the cells from cotyledon vascular bundles was evident. Only mesophyll cells near to the bundles were rich in plastids. In two-weeks-old intact bean plants, the cotyledons were yellow and shrunken, and their cells were nearly "empty". The plastids in them were represented by senescent plastids (gerontoplasts) only. In the gerontoplasts as well as freely in cytosol, fluorescent lipoid inclusions were accumulated. This cotyledon development was more or less independent of irradiance. In "decapitated" bean plants, senescence of mesophyll cells and plastids was slowed down considerably, and the life span of the cotyledons was prolonged. and J. Kutík, N. Wilhelmová, J. Snopek.
A proper understanding of tissue and cell structure is of great importance for correct biological inferences, and particularly so in organisms used as research models. Nothobranchius spp. are short-lived freshwater fish species which are promising model organisms for toxicology, evolutionary ecology, aging and regeneration research. Nevertheless, studies examining Nothobranchius histology have focused exclusively on a few specific organs and associated functional impairments, and there is a lack of reference material on the natural state and appearance of tissue structure. Here we present a detailed histological map of the major body organ systems, which was built from 300 Nothobranchius spp. specimens. This overview offers baseline material for comparative histological studies and provides insights into functional and anatomical aspects of organs related to the unique life cycle of Nothobranchius spp.