Abstracts |
In recent years, interest has grown in cultivating Allium species with enhanced
health benefits and/or distinct flavor. Concentrations of phytochemicals determining these
desired characteristics may be influenced by nitrogen forms (ammonium or nitrate) and arbuscular
mycorrhizal (AM) fungi. We examined these relations with the test plant bunching onion (Allium
fistulosum L.). Three different ammonium-to-nitrate (NH4+ : NO3-) ratios were supplied in
combination with or without inoculation with an AM fungus (Glomus mosseae). The plants were
evaluated for dry weight, leaf number, and content of nutrients (N, NO3-, P, S), sugars (glucose,
fructose, and sucrose), and organosulfur compounds (measured as pyruvic acid). The experiment was
carried out under controlled conditions in a greenhouse. Plants were grown on perlite amended
twice a day with nutrient solution. In nonmycorrhizal plants, the application of nutrient
solution with predominant NO3- or NH4NO3 as N source supported adequate growth of Allium
fistulosum while predominant NH4+ supply resulted in decreased growth and occurrence of wilting
symptoms. Mycorrhizal inoculation significantly increased dry weight and leaf number of
predominantly NH4+-fed or NH4NO3-fed plants. While shoot P concentration increased with higher
NH4+ supply, shoot N concentration increased in predominantly NH4+-fed plants only. Nitrogen form
and AM colonization had little effect on shoot S or sugar concentrations. The total content in
organosulfur compounds was significantly affected by both, N form and AM colonization. The
optimal growth condition for a high formation of organosulfur compounds in this experiment was a
nutrient solution with predominant,NO3- supply, but when supported by AM fungi, Allium fistulosum
produced similar amounts of pyruvic acid in NH4NO3-fed plants. |