It has been observed that under control conditions, the abscission of flowers in Phaseolus vulgaris proceeds via the breakdown of both the middle lamella and the primary wall of the cells in the abscission layer of the pedicel. However, under conditions of water stress, the dissolution of the middle lamella occurs much faster than the breakdown of the primary wall. The difference in the integrity of the cell wall of the abscising cells under these two conditions is discussed in relation to differential enzyme activation of the separation process.