Identification of Constraining Experimental-Design Factors in Mycorrhizal Pot-Growth Studies

Abstract

In the objective of testing the design of pot-growth experiments, we conducted two greenhouse studies of a “dwarf” sunflower cultivar and an arbuscular mycorrhizal (AM) fungus to determine how pot size and inoculum distribution affect plant growth and AM symbiosis. As predicted, large-potted plants developed a greater overall biomass and root colonization than small-potted ones which we attributed to the larger “rootable” volume. Furthermore, plants grown in a band of high density inoculum substrate showed a higher prevalence of fungal vesicles (sites of lipid storage) indicating a more advanced level of root colonization compared to those grown in a dispersed inoculum substrate; this likely being due to the higher frequency of interaction between roots and fungal propagules. In a second experiment, large-potted AM plants showed a greater tolerance to water deficit than non-AM control plants; however, this mycorrhizal effect was not detected among small-potted plants. We conclude that careful consideration should be made toward design parameters to limit result biases and ultimately facilitate comparison of findings between studies.