Involved in cell wall assembly during cell elongation. Endohydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans. Ubiquitous. By gibberellin (GA3) and brassinosteroid. Plants are dwarf with reduction in cell elongation and decrease in cellulose content. Belongs to the glycosyl hydrolase 9 (cellulase E) family.