ELSEVIER Plant Science 102 (1994) 41-47 plan cience Acid and enzymatic degradation of cell wall from epicotyls of Cicer arietinum L. A. Ramos, E. Labrador* Departamento de Biologia Vegetal (Fisiologia Vegetal), Facultad de Biologia, Campus Miguel de Unamuno, Universidad de Salamanca, Salamanca, E-37007, Spain Received 8 April 1994; revision received 15 July 1994; accepted 15 July 1994 Abstract In epicotyls of Cicer arietinum, there is a specific release of sugars when the cell wall is incubated at pH 1 (acid de- gradation). This process is distinct from the enzymatic cell wall autolysis which takes place at pH 5.5. The release is faster during the acid degradation and the products released are mainly polysaccharides with a high proportion of uronic acids, suggesting that this process may be due to a direct effect of protons on some pH-susceptible bonds be- tween galacturonic acid-rich pectic polysaccharides, bound by ionic forces mainly by calcium type linkages. The main neutral sugar released is arabinose with lesser amounts of galactose. These results indicate the involvement of different substrates than in the autolysis or enzymatic degradation where mainly galactose is released as a monosaccharide com- ponent. Cell walls previously subjected to an exhaustive enzymatic degradation, underwent the same degree of acid degradation as in the case in which the walls were intact, without prior enzymatic treatment, confirm that both substrates are not localized in the same polysaccharides. Thus, they would be two different and independent processes. Keywords: Autolysis; Cell wall; /~-Galactosidase; Pectins; Protons 1. Introduction The breakage of bonds between cell wall polysaccharides is responsible for the loss of wall rigidity that accompanies growth. Study of this bond breakage has been addressed from different points of view, although the phenomenon remains to be fully elucidated. Attempts have been made to correlate the breakdown of bonds between the wall polymers during cell extension with the * Corresponding author. hydrolysis of polysaccharides that occurs during the autolytic process of isolated cell walls. The enzymes and polysaccharides involved in this cell wall autolytic process have been identified in dif- ferent plant material. In monocotyledon plants, the cell wall autolysis is carried out by endo- and exoglucanases, which degrade a hemicellulosic mixed glucan. It is known that this polysaccharide is also involved in the processes of wall loosening and related to growth [1,2]. In other plants, e.g., the cell walls of tomato fruit [3], Pisum sativum epicotyls [4] and Cicer arietinum epicotyls [5], pec- 0168-9452/94/$07.00 © 1994 Elsevier Science Ireland Ltd. All rights reserved SSDI 0168-9452(94)03940-B