The effect of fungal infection and nitrogen fertilization on the carbohydrate composition of Rumex obtusifolius leaves

Abstract

The effect of infection by the rust fungus Uromyces rumicisand fertilization by different concentrations of nitrate or ammonium solutions on the concentrations of alcohol-soluble carbohydrates, fructans and starch in Rumex obtusifolius leaves was investigated. In leaves from healthy plants there was an increase in concentration of alcoholsoluble carbohydrates and fructans as the concentration of nitrate given was decreased, with the exception of nitrogen-stressed plants (those fed less than 10 mM l 1 nitrate) which had a lower concentration of alcohol-soluble carbohydrates than plants fed 10 mM l 1 nitrate. There was an increase in fructan and starch concentration in leaves as the concentration of ammonium solution given was decreased. The concentration of alcohol-soluble carbohydrates was reduced in infected leaves and increased in healthy leaves on infected plants, while the fructan concentration increased in infected leaves, compared to healthy leaves. The effects of infection were consistent over the range of nitrogen concentrations used, and thus were additive to the effects of fertilization. These results confirm the known effects of fertilization or fungal infection, singly, and indicate that, when combined, nitrogen deficiency and fungal infection may produce an additive stress on the plant.