What does ectodesmata mean?

Answer 1

Ectodesmata, sometimes referred to as ectoteichodes (or teichodes for short) are plant cell wall traversing areas. They are in fact the counterpart of plasmodesmata which are well established "open" membrane connections between the cytoplasm of adjacent cells. To demonstrate the presence of ectodesmata, plant tissues are fixed in a Hg-saturated fixative. Distinct Hg precipitates form on outer plant cell walls and show particular patterns on cross sections of wall fragments. It was assumed that these patterns are formed by non-uniform distribution of reducing agents along the walls. It was assumed further that the particular distribution of these reducing agents is a result of locally controlled excretion and/or extrusion. However, it has never been elucidated if ectodesmata are real physical structures. Research on this plant science subject started approximately in the 1930's and more or less ended in the 1970's as no one believed anymore that these "structures" were actually existent and had any biological significance. However, in 1995 a paper was published linking the presence of ectodesmata and deposits of callose in outer cell walls, thus resurrecting the incentive to re-address the possible biological significance of ectodesmata. ref: A relationship between callose and ectodesmata in epidermal cells of Allium cepa L. A.N.M. van Amstel (1995) Plant Cell Reports 15:707-711