Nitrate alters the flavonoid profile and nodulation in pea (Pisum sativum L.)

A rhizosphere application of NO_inf3^sup-and/or naringenin affected the Pisum sativum — Rhizobium leguminosarum biovar viciae symbiosis. NO_inf3^sup-(5 mM) lowered while naringenin raised the nodulation status (nodule numbers and weight) and nodule efficiency (C₂H₂ reduction activity). However, the inhibitory effect of NO_inf3^sup-was to some extent alleviated when applied in combination with naringenin. The plant biomass was increased by the application of NO_inf3^sup-and naringenin, either alone or in combination, while a higher root: shoot ratio was observed only in the naringenin-treated plants. Root flavonoids are known to regulate the expression of nod genes; their high-performance liquid chromatography profile was influenced in different ways by NO_inf3^sup-and naringenin.