Effect of cations on germination & germ tube development of Puccinia coronata uredospores.

Previous work in this laboratory (20) showed that germ tubes of Puccinia coronata uredospores would form structures in vitro resembling those found in infected host plants (18). This so-called vesicle formation occurred on Difco gelatin in the pH range of 6.2 to 6.9 on addition of 14 to 22 X 10-5 M Zn. Under these conditions germ tube length was reduced, and in some cases the percentage germination was lowered. Other metals, including Cd, Cu, Fe, Mg, Ca, Mo, Co, and Mn, did not replace Zn. Several preliminary observations in Sharp's work (19) and in the present study indicated gelatin contained substances affecting the action of Zn on germ tube growth and differentiation. A. The extent of vesicle formation varied with different gelatin samples. B. The concentration of Zn required increased with the gelatin concentration. C. A water extract of gelatin with added Zn stimulated vesicle formation on an agar substrate at pH 6.3 to 6.5 D. When gelatin was purified by water extraction, adding Zn failed to induce vesicle formation, and Zn inhibited germination at much lower concentrations. This paper reports further study of the action of Zn and gelatin under better defined conditions and presents evidence that both germination and vesicle formation are subject to cation effects.