NONINVASIVE IMAGING OF FUNGAL COLONIZATION AND HOST RESPONSE IN THE LIVING SAPWOOD OF SYCAMORE (ACER-PSEUDOPLATANUS L) USING NUCLEAR-MAGNETIC-RESONANCE

Non-invasive nuclear magnetic resonance (NMR) imaging techniques revea led anatomical features of healthy sycamore (Acer pseudoplatanus L.) s tems, the pathological anatomy of sooty bark disease [Cryptostrome cor ticale (Ell. and Everh.) Gregory and Waller] lesions, and the dynamics of fungal invasion and host response in excised lengths of living syc amore stems challenged with Ustulina deusta (Fr.) Petrak or Chondroste reum purpureum (Pers. ex Fr.) Pout. Infected wood and reaction zones c ould be distinguished clearly from healthy tissue in these images. Les ion development, observed by the sequential imaging of individual stem s, followed the course deduced from the destructive examination of a s et of similar stem lengths. U. deusta was unable to penetrate far into the living stem lengths, and responses chemically and morphologically similar to the reaction zones formed at the margins of naturally occu rring decay lesions were expressed at the interface between healthy an d colonized xylem. In contrast C. Purpureum rapidly invaded and killed excised stem lengths with little or no induction of characteristic re action zone responses. Calculated proton density (M(0)) images indicat ed that water levels in the reaction zones delimiting U. deusta lesion s were elevated by a factor of approximately 2.5-3.0. No such accumula tion of water occurred at the margin of C. purpureum lesions. The sign ificance of this in relation to xylem defence against fungal attack is discussed.