Effect of Ethylene on the Growth of Vesicular-Arbuscular Mycorrhizal Fungi and on the Mycorrhizal Formation of Trifoliate Orange Roots

Abstract

The effect of ethylene on the growth of vesicular-arbuscular mycorrhizal (VAM) fungi and the VAM formation of trifoliate orange roots was investigated. Spore germination and hyphal growth of VAM fungi were stimulated at concentrations ranging from 0.01 to 0.1 ppm ethylene. At 0.2 ppm and above, however, hyphal growth was severely inhibited. The rapid hyphal growth noted at 0.07 ppm ethylene treatment was severely retarded by ethylene absorbents. VAM development in trifoliate orange trees was markedly enhanced at 0.05 ppm ethylene, but was depressed at 1 ppm. At 0.05 ppm, tree growth was vigorous and leaf P content was high. Thus we propose that very low levels of ethylene play an important role in the hyphal growth of VAM fungi and in the infection and spread of the mycorrhizae.