Answer
Cellulose, lignin and suberin are the chemicals that provide rigidity to cell wall.
Step-by-step explanation
In plant two type of growth occurs, primary and secondary growth. in primary growth when new cells are formed they are bounded by primary wall whose composition in mainly of cellulose. in secondary growth accumulation of lignin in secondary wall, suberin in cork cell wall and lignin in xylem cell wall occurs which provide rigidity.