Responses of secondary metabolism in plants to nutrient deficiency

Abstract

Since levels of some compounds related to secondary metabolism show a sensitive response to nutrient deficiency, we studied the relationship between nutrient deficiency and disorder of secondary metabolism to find a new method of deficiency diagnosis. Deficiencies of N, P and K stimulated phenolic metabolism in rice (Oryza sauva L.) plants. N-deficient plants showed the most sensitive response; levels of some phenolic acids increased in N-deficient plants. In particular, levels of p-coumaric acid and ferulic acid in tops increased noticeably under N deficiency. Addition of Si in the medium decreased sinapic acid level in barley (Hordeum vulgare L.) plants when other nutrient condition were normal. Addition of Si suppressed the increase of phenolic acid levels caused by Mn excess in barley plants. Phenolic acids were analysed in seed coats of (i) field-grown broad been (Vicia Java L.) considered Ca deficient and (ii) plants grown in nutrient solutions containing different Ca concentrations. Sinapic acid and caffeic acid in the seed coats of green seeds increased prior to visual appearance of the browning symptom. Level of p-coumaric acid in the seed coats of the plants grown in 0.5 mM Ca solution was markedly higher than in those grown in 2.0 mM Ca solution. The findings suggest that analysing compounds of secondary metabolism, such as phenolic acids, provides a method for diagnosing nutrient disorders prior to the appearance of visible symptoms.