A plasmodesma, plural plasmodesmata, is a membrane-lined connection crossing a plant cell wall between neighboring cells. It provides a route for intercellular exchange, including movement of some signaling molecules and macromolecules. A plasmodesma contains a tubular strand of endoplasmic reticulum within its enclosing cell membrane; it is an organized cellular interface, rather than simply a hole in the wall.[ref]
Architecture and permeability of post-cytokinesis plasmodesmata lacking cytoplasmic sleeves by William J. Nicolas and others. Abstract: exchanged material, plasma membrane lining and internal ER strand
Transport changes during development. A cotton fibre study followed a fluorescent tracer from the seed coat into elongating fibres with confocal microscopy. Access through plasmodesmata was observed early, blocked around day 10 and observed again around day 16. Reverse tracer movement supplied a complementary test, distinguishing transport connectivity from the mere presence of a channel in a section.[ref]
The control of single-celled cotton fiber elongation by developmentally reversible gating of plasmodesmata and coordinated expression of sucrose and K+ transporters and expansin by Y. L. Ruan and others. Abstract; Figures1–2: tracer movement at different developmental stages and in opposite directions
The apparent width in an image is not the whole explanation of permeability. A 2017 electron tomography study found newly formed plasmodesmata with no visible open cytoplasmic sleeve, yet observed macromolecular diffusion. Architecture and transport must therefore be measured together.[ref]
Architecture and permeability of post-cytokinesis plasmodesmata lacking cytoplasmic sleeves by William J. Nicolas and others. Abstract: post-cytokinesis structure and macromolecular permeability
New to topics? Read the docs here!