Respiration of developing castorbean seeds

The rate of oil synthesis in the developing castor oil seed increased from 0.02 mg oil.day −1 .100 mg −1 (dry weight) at 6 days after fertilization to 3.84 mg.day −1 .100 mg −1 30 days after fertilization. Thereafter, it decreased with no oil synthesis occurring in seed 54 days after pollination. The rate of respiration of the seed was generally correlated with the rate of oil synthesis and peak respiratory rates of 71 μl O 2 and 125 μl CO 2 .h −1 .100 mg −1 (fresh weight) were observed in seeds 27 days after fertilization. The respiratory quotient increased from 1.2 in seed 12 days after fertilization to 1.7 to 1.9 during the period of most rapid oil synthesis. The C 6 /C 1 ratio was always less than 0.5 and indicated that the pentose phosphate pathway was operative at all stages of castor oil seed development.