The Root Cap as a Test System for the Evaluation of Golgi Inhibitors: II. EFFECT OF POTENTIAL INHIBITORS ON SLIME DROPLET FORMATION AND STRUCTURE OF THE SECRETORY SYSTEM

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Abstract
The effects of four potential inhibitors of dictyosome activity on the root cap secretory system were monitored by visual estimation of slime droplet reformation rates and by quantitative microscopy of the secretory cells. Only monensin was found to affect both droplet reformation and cell structure. While some of our structural observations on the effects of this drug, such as swelling of vesicles and dictyosome cisternae, agreed with those made previously, others did not. We are able to confirm a real increase in vesicle number, in addition to the numerical increase in vesicle profiles that follows from an increase in vesicle size. Formation of cup-shaped dictyosomes and separation of cisternae were found to be just as prevalent in the normal and in the solvent controls, especially when fixed with permanganate. Scopoletin, tunicamycin and 2, 6-dichlorobenzonitrile all affected droplet formation but had no significant effect on cell structure. It is suggested that these chemicals were affecting water flow into the slime droplet, rather than directly inhibiting Golgi-activity or release of carbohydrates by the secretory vesicles. The problems of using the root cap system for the identification of specific Golgi inhibitors are discussed.