Changes of ascorbate free radical reductase in pea roots infested by Heterodera goettingiana


  • G. Zacheo
  • R. Arrigont-Liso
  • T. Blevo-Sacheo
  • R. Arrigoni-Liso
  • F. Lamberti


There is much evidence which correlates ascorbic acid with plant resistance to various pathogens (Tonzig and Bracci, 1951; Gerola and Laudi, 1956; Farkas et al., 1960; Maine and Kelman, 1961; Van Lelyveld, 1975). Van Lelyveld (1975 a) suggested that ascorbic acid may be involved in the hypersensitive reaction in plant and the formation of lesions; mango fruits showing lesions as a result of bacterial infection had a lower level of ascorbic acid than in healthy plants. Decrease in ascorbic acid obtained by the application of lycorine, an inhibitor of ascorbic acid biosynthesis, was associated with a reduction of plant resistance to nematodes. On the other hand, the application of ascorbic acid to susceptible tomato plants rendered them partially resistant to Meloidogyne incognita (Arrigoni et al., 1979). Moreover, it has been demonstrated that the synthesis of ascorbic acid increased in resistant plants attacked by nematodes (Arrigoni et al., 1979). It seems, therefore, that ascorbic acid is utilized by the plant to activate the biological mechanisms of defence; during the process large quantities of ascorbic acid are oxidized as it functions as an electrons donor in the cell. Oxidation of the ascorbic acid (AA) results in the formation of two compounds through the successive loss of two electrons: ascorbic free radical (AFR), an intermediate compound after the loss of the first electron, and dehydro ascorbic acid (DHA), the final product of the reaction. Of the two, only AFR can efficiently be reconverted into AA because of the action of the AFR reductase (EC present in the cells, which catalizes transfer of electrons from NADH (a-Nicotinamide Adenine Dinucleotide) to AFR (Arrigoni et al., 1981). The aim of the work described here was to determine differences in the AFR reductase activity between pea (Pisum sativum L.) lines susceptible or partially resistant to the pea cyst nematode, Heterodera goettingiana Wollenweber, and to ascertain if enzymatic activity varies during nematode attacks.