Alleviation of drought stress by mycorrhizas is related to increased root H(2)O(2) efflux in trifoliate orange

The Non-invasive Micro-test Technique (NMT) is used to measure dynamic changes of specific ions/molecules non-invasively, but information about hydrogen peroxide (H(2)O(2)) fluxes in different classes of roots by mycorrhiza is scarce in terms of NMT. Effects of Funneliformis mosseae on plant growth, H(2)O(2), superoxide radical (O(2)(·−)), malondialdehyde (MDA) concentrations, and H(2)O(2) fluxes in the taproot (TR) and lateral roots (LRs) of trifoliate orange seedlings under well-watered (WW) and drought stress (DS) conditions were studied. DS strongly inhibited mycorrhizal colonization in the TR and LRs, whereas mycorrhizal inoculation significantly promoted plant growth and biomass production. H(2)O(2), O(2)(·−), and MDA concentrations in leaves and roots were dramatically lower in mycorrhizal seedlings than in non-mycorrhizal seedlings under DS. Compared with non-mycorrhizal seedlings, mycorrhizal seedlings had relatively higher net root H(2)O(2) effluxes in the TR and LRs especially under WW, as well as significantly higher total root H(2)O(2) effluxes in the TR and LRs under WW and DS. Total root H(2)O(2) effluxes were significantly positively correlated with root colonization but negatively with root H(2)O(2) and MDA concentrations. It suggested that mycorrhizas induces more H(2)O(2) effluxes of the TR and LRs, thus, alleviating oxidative damage of DS in the host plant.