Impact of egyptian broomrape (Orobanche aegyptiaca (Pers.) parasitism on amino acid composition of carrot (Daucus carota L.).

The relationship between the organic nitrogen status of Egyptian broomrape and one of its hosts, carrot, was studied by comparing amino acid profiles of leaf and root tissues of nonparasitized and broomrape-parasitized carrot plants and by analyzing amino acid profiles of broomrape at different growth stages. Total N concentrations, expressed as a percentage of the dry weight of the tissues, were similar in leaves of nonparasitized and parasitized carrot plants but were lower in parasitized roots than in nonparasitized roots. In both dry and germinated broomrape seeds, N concentrations were lower than or similar to those in broomrape tubercles, shoots, or callus. Individual amino acid concentrations in hydrolysates of leaves of parasitized carrot plants tended to be similar to or greater than those in hydrolysates of nonparasitized carrot plants. Roots of parasitized plants tended to have similar or lower amino acid concentrations than roots of nonparasitized plants. Dry and germinated broomrape seeds had similar amino acid profiles, but individual amino acid concentrations were lower than in the other broomrape tissues examined. The broomrape shoot tended to have lower amino acid concentrations than the tubercle and callus. Free amino acid profiles of leaves and roots of parasitized plants paralleled those of nonparasitized plants, respectively. Individual free amino acids tended to occur at similar or lower levels in dry and germinated broomrape seeds than in the tubercle, shoot, or callus. Free amino acid composition of the broomrape tubercle was similar to that of the parasitized root. Arginine and alanine concentrations in broomrape callus were dramatically higher than those of other amino acids in this or other tissues investigated. These results indicate that changes in the composition of both free and bound amino acids in carrot are associated with broomrape parasitism.