 One product of this is reinforcement of the cell wall in an attempt to stop the invasion.The plant starts forming the papillae - a callose matrix (cellulose, suberin, protein, gums, calcium and silicon) which provides extra resistance to penetration, however this barrier does remain effective for long if the level of micro-organisms present is high.Wheat cells also release hydroxyproline glycoprotein (HRGP) in their cell walls.