Double pot and double compartment: Integrating two approaches to study nutrient uptake by arbuscular mycorrhizal fungi

The double compartment technique has been commonly used in studies on nutrient uptake by mycorrhizas whereas the double pot technique has been used to assess the nutritional stress of plants grown in different soils. A combination of the double pot and the double compartment technique was used as a tool to understand the processes involving mycorrhiza and plant nutrition. Maize (Zen mays) and three species of the arbuscular mycorrhizal fungi in the genus Glomus were used to study phosphorus (P) uptake with and without mycorrhiza from the A and B horizons of an Oxisol. The plants were supplied from the lower pot with a nutrient solution without P. The upper pot had a double compartment with either a fine and coarse mesh screen to control the volume of soil explored by the roots, and thereby, limit the amount of soil P accessible to plants from the test soil. There were significant effects of time for plants grown in both soil horizons, and of mycorrhizas for plants grown in the A soil horizon. No effect of mesh size was observed. There were significant effects of horizon and mycorrhiza, but not of mesh size, on the dry weight and P contents of shoots and roots. The P concentration (P g kg(-1) of plant) for shoots and roots was similar in the A and B soil horizons. The results showed that the double pot - double compartment system was suitable for the experimental objectives. No differences in plant growth were observed when root growth was not limited vs root growth limited to the inner compartment because the non-mycorrhizal plants did not take up P. Consequently, responsiveness of the maize cultivar was wholly dependent on mycorrhiza for P uptake under these experimental conditions.