<P> Plasmodesmata ( singular : plasmodesma ) are microscopic channels which traverse the cell walls of plant cells and some algal cells , enabling transport and communication between them . Plasmodesmata evolved independently in several lineages , and species that have these structures include members of the Charophyceae , Charales , Coleochaetales and Phaeophyceae ( which are all algae ) , as well as all embryophytes , better known as land plants . Unlike animal cells , almost every plant cell is surrounded by a polysaccharide cell wall . Neighbouring plant cells are therefore separated by a pair of cell walls and the intervening middle lamella , forming an extracellular domain known as the apoplast . Although cell walls are permeable to small soluble proteins and other solutes , plasmodesmata enable direct , regulated , symplastic transport of substances between cells . There are two forms of plasmodesmata : primary plasmodesmata , which are formed during cell division , and secondary plasmodesmata , which can form between mature cells . </P>
what are plasmodesmata and what is their function
microscopic channels which traverse the cell walls of plant cells and some algal cells , enabling transport and communication between them