Fine Structure and Cytochemistry of the Abscission Zone Cells of Phaseolus Leaves

Abstract

The fine structure of the separation zone cells from the basal abscission zone of bean leaves has been described. Examination of these cells revealed that fracture occurred primarily as a result of the dissolution of the middle lamellar region of the walls, leaving intact cells on the two newly exposed fracture surfaces. The cytoplasm and organelles within these cells appeared quite normal and showed no signs of autolysis or senescence. A comparison of the organelle numbers in these cells with cells from a similar region of a control plant revealed large increases in the number of Golgi bodies and the amount of rough endoplasmic reticulum. The significance of this finding is discussed in relation to the secretion of cell wall hydrolysing enzymes which are known to be produced in these cells.