DEHISCENCE OF FRUIT IN OILSEED RAPE (BRASSICA-NAPUS L) .2. THE ROLE OF CELL-WALL DEGRADING ENZYMES AND ETHYLENE

Pod shatter in oilseed rape is accompanied by the degradation of the cell wall at the site of fruit dehiscence. Cell separation is preceded by an increase in the activity of the hydrolytic enzyme cellulase (β 1,4-glucanase, E.C. 3.1.2.4), and this rise in enzyme activity is restricted to the dehiscence zone cells. In contrast, the activity of the cell wall degrading enzyme polygalacturonase (E.C. 3.2.1.15) exhibits no correlation either temporally or spatially with pod dehiscence. An analysis of the ethylene production profile by intact pods during maturation has revealed the existence of an ethylene climacteric and this is temporally correlated with the tissue-specific increase in cellulase activity. The major site of ethylene production by the fruit has been identified to be the developing seed. Since maintenance of intact pods in ethylene accelerates both the senescence and dehiscence of the tissue, it is possible that this gaseous regulator plays an important role in the process of pod shatter in vivo. © 1990 Oxford University Press.