Abstract
Emergence and establishment of seedling of paddy rice sown into flooded soil are poor but promoted when seeds are coated with O2 generator CaO2. It has been commonly understood that this is because CaO2 supplies O2 to the seed germinating in the anaerobic flooded soil. However, it is known that even in CaO2-coated seed, emergence of foliage leaf is restrained unless O2 is supplied from flooded water or air through coleoptile after seedling emergence. The effect of seed coating with KNO3, which generates no O2 by itself but oxidizes soil, on emergence and establishment of seedling of paddy rice sown into flooded soil was investigated. In KNO3-coated seeds, emergence and establishment of seedling began earlier, and the percentage of seedling emergence and of foliage leaf emergence were higher than in non-coated seeds. KNO3 showed much the same or a rather more conspicuous effect than CaO2 at lower temperature. These results suggest that the major cause of the poor emergence and establishment of seedling in paddy rice sown into flooded soil is not O2 deficiency in flooded soil. Thus, whether O2 supply to a seed is essential for, and why CaO2 is effective for, promotion of emergence and establishment of seedling would have to be examined in further more details.
