1995 Volume 45 Issue 3 Pages 301-307
Immature pollen grains of an Indica type rice cultivar IR24 were isolated and cultured to regenerate green plants without preculture of anthers. Either low-temperature pretreatment of panicles at 10'C in the dark or exposure to sugar starvation in the beginning of culture were necessary for induction of cell division of the grains. Low-temperature pretreatment was more effective treatuent than exposure to sugar starvation. It was found that there was a complementary relationship between the effects of low-temperature pretreatuent and of exposure to sugar starvation the pollen grains required shorter period of exposure to sugar starvation to start cell division as low-temperature pretreatnent was prolonged. The optimal condition for induction of cell division of the pollen grains was 21 days of the pretreatuent with I day of sugar starvation or 28 days of the pretreatment without sugar starvation. Though 2, 4-D was not necessary for induction of cell division, the development of the derived colonies followed by shoot regeneration was observed only in the presence of 2, 4-D. Reduced nitrogen source in the induction medium also affected the frequency of both colony formation and plant regeneration. The medjum containing 20mM KN03 and 5mM glutamine as nitrogen sources gave the highest frequency of colony formation at 0.20/0 and its frequency reached 2.0 times higher than the control R2 medium containing 40mM KN03 and 2.5mM (NH4)2S04. On the other hand, the calli which were formed in the medium containing 20mM KN03 and 5mM alanine had the highest regenerating ability. In addition, the calli which were formed in the medium containing 20mM KN03 and 5mM alanine showed marked higher frequency of green plant regeneration than ones in any other media tested, when 21 days of low-temperature pretreatment without exposure to sugar starvation was applied as induction condition.