The changes in cell wall polysaccharides and selected cell wallmodifying enzymes were studied during the development of green bean (Phaseolus vulgaris L.) pods. An overall increase of cell wall material on a dry-weight basis was observed during pod development. Major changes were detected in the pectic polymers. Young, exponentially growing cell walls contained large amounts of neutral, sugar-rich pectic polymers (rhamnogalacturonan), which were water insoluble and relatively tightly connected to the cell wall. During elongation, more galactose-rich pectic polymers were deposited into the cell wall. In addition, the level of branched rhamnogalacturonan remained constant, while the level of linear homogalacturonan steadily increased. During maturation of the pods, galactose-rich pectic polymers were degraded, while the accumulation of soluble homogalacturonan continued. During senescence there was an increase in the amount of ionically complexed pectins, mainly at the expense of freely soluble pectins. The most abundant of the enzymes tested for was pectin methylesterase. Peroxidase, ␤-galactosidase, and ␣-arabinosidase were also detected in appreciable amounts. Polygalacturonase was detected only in very small amounts throughout development. The relationship between endogenous enzyme levels and the properties of cell wall polymers is discussed with respect to cell wall synthesis and degradation.The texture of processed vegetables and fruits is in part determined by the properties of the cell wall and the middle lamella (Stolle-Smits et al., 1997). The cell wall is not a static structure, it is dynamic in nature. Its composition and structure change continuously during plant development. Plant cell walls consist of cellulose microfibrils coated by xyloglucans and embedded in a complex matrix of pectic polysaccharides (Talbot and Ray, 1992;Carpita and Gibeaut, 1993). Pectic substances are abundant in fruit and vegetable cell walls and are considered to be important in determining the texture of processed vegetables. Cell wall pectin consists of two regions, a linear homogalacturonan (HGA) and a branched rhamnogalacturonan. Neutral side chains, mainly consisting of arabinosyl and/or galactosyl residues, are attached to the rhamnogalacturonan backbone in variable amounts. In addition, xylosyl units can be linked to the GalUA backbone, as was reported for branched apple pectins (Schols et al., 1995).RGII is a very typical branched pectin that occurs only in minor amounts and is suggested to function as a signal molecule (Darvill et al., 1978). The carboxyl and hydroxyl groups of the GalUA backbone can be substituted with methyl and acetyl esters, respectively. Pectin is believed be connected to other cell wall components or other pectins by ionic and covalent cross-links (Brett and Waldron, 1990). The exact nature of these cross-links is still unknown, but cross-linking esters are thought to be involved. The aim of this study was to analyze the modifications of cell wall composition in green bean (Phaseolus vulgaris ...