Fig. 1.

Experimental set‐up designed to test the movement of water to plants by arbuscular mycorrhizal fungi (AMF) hyphae. (a) AMF permitted ¹⁸O + dye microcosms (‘+AMF’) where AMF are able to access a no‐plant compartment, and ¹⁸O‐labeled water and fluorescent dye lucifer yellow carbohydrazide (LYCH) injected into the no‐plant compartment. (b) Arbuscular mycorrhizal fungi excluded ¹⁸O + dye microcosms (‘−AMF’) where AMF are not able to access the no‐plant compartment, and ¹⁸O‐labeled water and fluorescent dye LYCH injected into the no‐plant compartment. (c) Arbuscular mycorrhizal fungi permitted ¹⁶O + no dye microcosms (‘¹⁶O’) where AMF are able to access the no‐plant compartment, and unenriched water without a fluorescent dye is injected into the no‐plant compartment. In (a–c): 1, Avena barbata shoots; 2, A. barbata roots; 3, AMF Rhizophagus intraradices; 4, Plant compartment filled with ½ sand : ½ clay mixture; 5, 3.2 mm air gap; 6, No‐plant compartment filled with ½ soil : ½ sand mixture; 7, Syringe illustration of injection of solutions into the no‐plant compartment.