Monzer J, Haindl E, Kern V, Dressel K
Lehrstuhl fur Botanik, Technische Universitat Munchen at Weihenstephan, Freising, Germany.
Exp Mycol. 1994 Mar;18(1):7-19. doi: 10.1006/emyc.1994.1002.
The fruiting body of the basidiomycete Flammulina velutipes shows a distinct negative gravitropic response. Maturing fruiting bodies in the rapid elongation phase become graviresponsive with basidiospore differentiation. Lateral gravistimulation by horizontal arrangement of the fruiting body results in unilateral growth regulation. Elongation in the upper Stipe side decreases to 40% during gravitropic reorientation of the fruiting body. Overshooting of the gravitropic response during reorientation is precisely regulated. The graviresponsiveness is concentrated to the apical area of the stipe, the transition zone between pileus and stipe, which features a prominent elongation capability. The small size and low vacuolization of the transition zone hyphae compared with differentiated basal stipe hyphae correspond with this physiological function on the light and electron microscopical levels. Curvature experiments using intact and explanted fruiting bodies demonstrated the graviperceptive role of the transition zone. The excision of various amounts of pilear tissue, even the disruption of the whole pileus, had no severe effect on gravitropic curvature, until the transition zone was damaged. Removal of the transition zone resulted in a dramatic loss of graviresponse, whereas the decrease of elongation was less drastic.
担子菌金针菇的子实体表现出明显的负向重力性反应。处于快速伸长阶段的成熟子实体在担孢子分化时开始对重力产生反应。通过水平放置子实体进行侧向重力刺激会导致单侧生长调节。在子实体重力重新定向期间，菌柄上部一侧的伸长率降至40%。重新定向期间重力反应的超调受到精确调节。重力反应集中在菌柄的顶端区域，即菌盖和菌柄之间的过渡区，该区域具有显著的伸长能力。与分化的基部菌柄菌丝相比，过渡区菌丝的体积小且液泡化程度低，这在光学和电子显微镜水平上与该生理功能相对应。使用完整和离体子实体进行的弯曲实验证明了过渡区的重力感受作用。切除不同量的菌盖组织，甚至整个菌盖的破坏，对重力弯曲都没有严重影响，直到过渡区受损。切除过渡区会导致重力反应急剧丧失，而伸长率的降低则不那么剧烈。
