Influence of Mycorrhizal Fungi on Cytokinin Production in Sour Orange

Abstract

Abstract Nonmycorrhizal or mycorrhizal ( Glomus fasciculatum , G. etunicatum , or Gigaspora heterogama ) sour orange ( Citrus aurantium L.) seedlings were fertilized with 3 phosphorus levels applied in the irrigation water. At 0 mg P/L fertility, dry weight and cytokinin production of mycorrhizal plants were more than twice those of the nonmycorrhizal plants. Concentrations of P in leaves of mycorrhizal plants also were greater than the concentrations of P in the nonmycorrhizal plants. At 50 mg P/L fertility, concentrations of P in leaves were similar whether or not plants were mycorrhizal. Dry weight and cytokinin production of the mycorrhizal plants, however, were still twice those of the nonmycorrhizal plants. At 100 mg P/L fertility, dry weight and cytokinin production did not differ between nonmycorrhizal plants and plants infected with 2 of 3 mycorrhizal fungi. In G. heterogama- infected plants, cytokinin production was greater than that of nonmycorrhizal plants despite similar dry weights and P concentrations in the leaves. Enhancement of cytokinin production seemed to be associated with mycorrhizal infection rather than with increased P uptake.