Abstract
Summary: Results from experiments on clover (Trifolium pratense L.) and leek (Allium porrum L.) revealed that removal of extraradical hyphae from vesicular‐arbuscular mycorrhizal (VAM) plants had a detrimental effect on transpiration flux. The advantage of comparisons between VAM plants with and without extraradical hyphae rather than between VAM and non‐mycorrhizal plants is discussed in relation to this type of investigation. It is suggested that extraradical hyphae increase the root absorptive‐surface area, independently of an enhanced nutrient status.