Investigations were undertaken on the effects of respiratory inhibitor upon the growth of rice plant. Constant volume of the solution saturated by H2S were added to the nutrient solution of water culture of rice plants. The external and internal changes in the root observed were as follows. 1) Root growth was inhibited by H2S and the parts severely injured showed necrosis 2) From the parts just above the necrotic portion, many lateral roots grew forming a bunch like a lion's tail in its appearance. 3) Occasionally in old roots the lateral roots were hindered, by the exoderm that had been strongly ligified, from protruding outside, and elongated themselves into the lysigenous intercellular spaces of the cortex. (Eig. 1 and 2). Such phenomena took place by solution cultures both with and without H2S. Therefore, it may be understood that the anaerobic condition of culture solution was the direct cause for the root injury, and H2S might have promoted it.
