| Abstract: | Concentrations of both free and conjugated indole-3-acetic acid(IAA) were studied during development of pod wall, dehiscencezone and seeds of Brassica napus pods. A decrease in auxin contentprior to moisture loss in the pods was observed specificallyin the dehiscence zone, which was correlated with a tissue specificincrease in ß-1,4-glucanase activity. Furthermore,treatment of the pods with the auxin mimic 2-methyl-4-chlorophenoxyaceticacid resulted in a delay of 10 d of ß-1,4-glucanaseactivity and con-comitant cell separation in the dehiscencezone. This indicates that the activity of hydrolytic enzymesinvolved in cell separation in the dehiscence zone is regulatedby auxin activity. Comparison of parthenocarpic pods with seeded pods pointed tothe seeds as the source of IAA. Levels in the dehiscence zoneof these pods were low over the entire sampling period, whilecell separation in the dehiscence zone was delayed by about4 d. These results indicate that a low level of auxins in thedehiscence zone is necessary for dehiscence to take place, butother factors may also be important. Key words: Brassica napus, pod dehiscence, auxin, cellulase |
