Abstract
The sclerotia of Pellicularia sasakii produced on rice plants at an early stage of development sink under water after dropping from the rice plants, but float on water surface with maturing within one month after formation. Experiments were carried out for elucidating the floating structure of natural and cultured sclerotia (PDA).
The structure of floating sclerotia has two distinct layers, inner and outer layers. The inner layer consists of mass of living cells and the outer layer of empty cells. The width of the outer layer is over 200μm. The outer layer of sinking sclerotia is narrow with less than 150μm and surrounded by hyphal cells. All sclerotia of this size sink under water but they float slightly with aging. The floated sclerotia has a wider outer layer and do not have a layer of hyphal cells. On the other hand, the outer layer of cultured sclerotia is narrower, and can not float on the water surface. On the part of the outer layer, the hyphal cells can be clearly seen.
From these results, it is concluded that the floating on the water surface of the sclerotium is associated closely with the structure of the outer layer.
