Forisome

Forisome (from Latin foris = " door " and the Greek soma = " body " ) are protein complexes from the sieve elements of the pea family. In wounding the phloem they experience a conformational change that results in the phloem sieve tubes to the closure of the affected.

Forisome provide a specific for the subfamily of Faboideae class of P- proteins; they consist of several subunits, the so-called Forisometten, which in turn are composed of several proteins. In differentiated sieve elements Forisome are as an elongated complex of about 30 microns in length. By increasing the Ca2 concentration or pH, as they occur in an injury of the vascular bundles, there is a conformational change of the normally crystalline to a dispersed form, which completely close within seconds the screen plates and thus a loss of transported in the phloem assimilates can prevent. The conformational change is reversible and does not require the presence of the cellular adenosine triphosphate energy storage. Also, abrupt changes in the osmotic value or the presence of detergents trigger the conformational change.