FUNCTIONAL-ANATOMY OF THE MECHANORECEPTOR CELLS IN TENDRILS OF BRYONIA-DIOICA JACQ

The ultrastructure of epidermal cells of tendrils of Bryonia dioica Ja cq. (Cucurbitaceae) was determined using microscopic, histochemical an d immunochemical techniques with focus on the tactile blep, the mechan oreceptor of these cells. Tactile bleps resemble bordered pits in stru cture and probably in formation. They contain cytoplasm rich in endopl asmic reticulum, dictyosomes, mitochondria and microbodies. The cytopl asm is highly vesiculated and usually contains lipid-body-like structu res. Cytoskeletal elements (microtubules, actin filaments) are uniquel y arranged in the tactile blep, and chlorotetracycline-fluorescence an alysis shows large amounts of membrane-associated calcium within the t actile blep. We propose a physically interconnected cytoskeleton-membr ane device as the immediate force sensor and transducer which creates a primary intracellular signal, for which calcium is a likely candidat e.