Root uptake capacity of ammonium, nitrate, and glycine in red and white oak seedlings colonized by different species of ectomycorrhizas

While plant nitrogen (N) status often correlates positively with the extent of root mycorrhizal colonization in mature trees, fungal effects on nutrient status of seedlings are less understood. Furthermore, whether mycorrhizal species differ in their effects on seedling N uptake is not known. Here, we examined the effects of six ectomycorrhizal species on root uptake capacity of ammonium, nitrate and glycine in red and white oak seedlings. Acorns were germinated and subsequently individual seedlings were infected with one of the six species of fungi for four months before uptake studies were conducted. Regardless of species of plants or fungi, colonization decreased uptake capacity of inorganic N forms. Across mycorrhizal species root uptake rates of red oak decreased by an average of 57 and 39% for ammonium and nitrate respectively. This negative effect of colonization was even more pronounced in inorganic N uptake of white oak averaging to a decrease of 72 and 61% for ammonium and nitrate respectively. Root colonization had an opposite effect on amino acid uptake i.e., glycine uptake rates were on average 39% greater in mycorrhizal than control plants in red oak with no significant effects in white oak. The results have significant implications for understanding mycorrhizal control of N capture during early stages of plant development.