Effects of Grafting on Stipe Elongation and Pileus Expansion in the Mushroom Flammulina Velutipes

In fruitbodies of Flammulina velutipes growing on nutrient-supplemented sawdust the pilei were replaced on whole stipes and pilei with stipe apices (2 mm) were grafted in various ways to subapical stipe portions at the beginning of rapid elongation. Hyphal regeneration and fusion occurred in 84–100% of the grafts attempted but stipes and pilei resumed growth in only 28–94%. In whole stipes with replaced pilei elongation almost equalled that of intact fruitbodies, while pileus expansion virtually ceased for two days before resuming. In all other successful grafts rapid growth of both stipe apex and pileus resumed after a delay of 2–3 days, while all stipe portions below the top graft union stopped growing early as did unsuccessful grafts and controls without pilei. Pilei and stipe apices grafted on inverted stipe segments to the base grew as much as with normally oriented ones. Killed segments stopped all apical growth. No primordia regenerated on grafted specimens.The effects of the various grafts are explainable in terms of acropetal transport of mycelial metabolites through living hyphae under the influence of the pilei. Results are also discussed in relation to the control of stipe elongation by the lamellae.