Growth and Rotation of Flammulina Velutipes Fruit Bodies and the Dependence of Stipe Elongation on the Cap

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Abstract
SUMMARY Flammulina velutipes fruit bodies were grown on potato dextrose agar under continuous light. Fruit body growth was better on mycelium transferred from 21 ± 1 C to 16 ± 1 C than in cultures maintained continuously at the higher temperature. However, large fruit bodies also formed at 21 ± 1 C. Growth curves are presented for stipe elongation and cap expansion at 16 ± 1 C, and spiral growth of the stipe was measured by the rotation of the cap. The maximum speed of rotation varied considerably (15-50°/12 hr), and, at least up to 3 cm fruit body length, the preferred direction of rotation was clockwise as viewed from above. Reversal from clockwise to counter-clockwise rotation was observed in 2 of 10 fruit bodies. Decapitation of fruit bodies at different lengths caused a rapid decrease in stipe elongation without recovery, and demonstrated that stipe growth depends on the cap during most of the growth period. This dependence was strongest in younger fruit bodies but was detectable even at 7–7.9 cm, the upper limit tested. Removal of approximately 5 of the cap, leaving only a narrow symmetrical cap slice with lamellae, reduced growth significantly in young fruit bodies of 1.5-2.4 cm length, but not at close to 3 cm. Growth studies after removal of either the lamellae or the cap trama from cap slices showed that stipe elongation depends on the lamellae and not on the cap trama. Unexpectedly, the stipes did not curve either in darkness or in light, despite continuing elongation, when half cap slices with lamellae were left attached to one side of stipes at 1.2-3.7 cm length. Half of the whole cap also failed to induce negative curvature. The findings for Flammulina velutipes are compared with those reported for Agaricus bisporus.