Parental exposure to high and low temperatures during seed development modified the growth pattern of rice seedling in next generation. Whereas the after-effects of daylength given to parents on the seedling growth were not detectable, except the effect of daylength under high temperature. Shoot, root and mesocotyl growth of Japonica and Indica rice were increased by the parental exposure to high temperature, irrespective of the difference of photoperiod sensitivites among rice cultivars.
Conditioning by different temperatures during seed formation induced the greater fluctuation of the mesocotyl growth in Japonica than in Indica rice. Coleoptile growth of Indica rice and that of Japonica rice in southern part of Japan tended to be promoted by lower temperature pretreatments, while Japonica rice in northern part of Japan was not affected by temperatures. The relationships between the growth response of coleoptile and mesocotyl to the temperature during seed formation of parental plant and the habitats of rice ecospecies, Indica and Japonica, are discussed in this paper.