We study the avalanche dynamics of micron-sized starch-filled amyloplasts (statoliths) that sediment in some dedicated plant cells (statocytes) and play an important role in gravity detection by plants. Microscopic observations of wheat coleoptiles cuts show that, contrary to a classical granular material, a pile of statoliths flows easily, even in response to small inclination angles. This flowability is enhanced be any source of agitation in plants cells (e.g. thermal agitation, cytoskeleton activity) and might explain the high sensitivity of plants to gravity. The use of a "biomimetic" microfluidic chambers filled with silica micro-particles enables us to do direct comparison between motions of statoliths in wheat cells and inert particles of same dimension only submitted to thermal agitation. The dynamics of piles angles suggest that the high flowability of statoliths cannot be explained by the sole thermal motion and is mostly due to biological active motions in plant cells. This conclusion is also supported by the observed difference between single trajectories of statoliths and silica particles at the top of a pile at rest: the amplitude of statoliths motion in wheat cell exceed by a factor ∼10 those of an inert particle of the same weight.