A comparison of visualization techniques for recording arbuscular mycorrhizal colonization

The extent of arbuscular mycorrhizal colonization was assessed in 10 field- collected plant species, representing three annual forbs, three perennial f orbs, three perennial grasses and one annual grass. Each root system of eac h plant was split into four portions, and for each portion, mycorrhizal str uctures were revealed with epifluorescence microscopy (under which only arb uscules are generally visible) and three commonly used stains (Chlorazol Bl ack E, Acid Fuchsin and Trypan Blue). The aim of the study was not to evalu ate the efficacy of each method, but to compare results obtained by each un der standard laboratory conditions. The recorded colonization levels of arb uscules, total arbuscular mycorrhizal fungal material and total fungal (arb uscular mycorrhizal + non-arbuscular mycorrhizal) material differed signifi cantly between visualization methods in a number of species. However, there were also interactions between stain and plant species, indicating that th e performance of a stain is dependent on the plant species being examined. In some cases (e.g. Plantago lanceolata), each visualization method produce d the same colonization level, while in others (e.g. Dactylis glomerata), e ach method gave a different result. These data therefore suggest that the l evel of mycorrhizal colonization recorded in any particular plant species a t a particular time is dependent on the technique employed.