Graviresponding sites in shoots of normal and‘lazy’rice seedlings

We have examined the graviresponding sites in the shoots of seedlings of rice ( Oryzasativa L.) and their relation to the agravitropic growth of a‘lazy’line. The graviresponding sites of the seedling shoots of a japonica type of rice. cv. Kamenoo. shifted from the mesocotyl/coleoplile region to the leaf‐shealh base when the shoots grew in the dark. A lazy line ot rice. lazy‐Kamenoo. showed gravicurvature in the mesocotyl/ coleoptile region at the early stage of growth, hut eventually lost its graviresponse as the seedlings grew. The loss of graviresponsiveness of lazy‐Kamenoo was attributed to a reduced response of the coleoptile and a diminished response of the leal‐sheath base to gravity. Later. the leaf‐sheath base of lazy‐Kamenoo became gravitropically incompetent. causing agravitropic growth of the shoots. Thus, shoots of lazy‐Kamenoo lose graviresponsiveness in an organ‐dependent fashion.