Plant‐induced pH changes in the rhizosphere of “Fe‐efficient” and “Fe‐inefficient” soybean and corn cultivars

Abstract

In intact root systems of soybean and corn cultivars differing in Fe efficiency the pH gradients at the soil‐root interface (rhizosphere) have been studied. For this purpose a combination of an agar technique (fluid agar + pH indicator) and a soil culture (sandy soil, pH 6.0) were used. In addition the rhizosphere pH was measured with antimony microelectrodes.

With this method, striking differences in rhizosphere pH could be observed both between the cultivars and within a cultivar along the root system. In general, the rhizosphere pH was higher in “Fe‐inefficient”; cultivars compared to “Fe‐efficient”; cultivars. Compared to the bulk soil (pH 6.0) the rhizosphere pH in the basal root zones of Fe‐inefficient cultivars (PI‐54169; ys₁/ ys₁) increased up to pH 7.5 and pH 6.8, respectively; the corresponding pH values for the Fe‐efficient cultivars (Hawkeye; WF9) were pH 6.8 and pH 5.6, respectively. Within the root system of the same plant the rhizosphere pH of apical zones was always more than one pH unit lower than in the basal root zones. The method presented in this paper for measuring pH changes in the rhizosphere offers a simple and rapid way for detailed studies of root‐induced changes in the rhizosphere in general.

Key words:

• Fe‐efficiency
• chlorosis resistance
• rhizosphere
• pH changes
• cation/anion uptake
• soybean
• corn