Nutrient Foraging by Mycorrhizal Roots of Different Morphology: Are Roots and Fungi Complementary?

David M. Eissenstat and Roger T. Koide.
NSF IOS-1120482.
Duration: 2011-2015.

The traits of roots that influence nutrient foraging across plant families are poorly understood. In most plant species, roots form a symbiotic association with mycorrhizal fungi that may improve the ability of the plant to forage for nutrients. Species differ in the extent that mycorrhizas can benefit nutrient acquisition, and this is likely related to root morphology, including root diameter and root hair abundance. The PIs hypothesize that tree species with magnolioid-type roots (coarse and with few or short root hairs) primarily forage in nutrient-rich patches using mycorrhizal fungal hyphae and that tree species with graminoid-type roots (more rapidly growing and producing many long root hairs) do so primarily by proliferating roots, increasing root hair development and altering nutrient uptake kinetics. The project will be primarily conducted in a 14-year-old planting of 16 different tree species that vary widely in root morphology, although additional studies will be conducted in natural forest stands and in growth chambers. This study will improve the theoretical basis by which plant roots can be used for scaling the influences of vegetation on elemental cylces, needed for better predictions of vegetation responses and feedbacks to climatic change as well as improve the understanding of roots needed for managing crops for food and fiber. There will be a strong educational component to this research, including the training of three graduate students, undergraduate training in research and international exchanges.

Nutrient Foraging Project

Figure 1. Morphology of absorptive roots of co-occurring AM trees in central Pennsylvania. Top row, left to right: Magnolia acuminata (Maac), Liriodendron tulipifera (Litu), Juglans nigra (Juni). Bottom row, left to right: Fraxinus americana (Fram), Acer rubrum (Acru) and Ulmus americana. All roots are of the same magnification (2nd-order Maac is about 1 mm in diameter). We hypothesize that species with coarse absorptive roots primarily forage by mycorrhizal hyphae proliferation whereas species with fine roots forage primarily by root proliferation