The development of polysomes in the seed of Pisum arvense.

1. Ribosomal preparations from dormant seed, cotyledon and growing tissue from Pisum arvense were examined. 2. Polysomes were obtained from growing tissues under all conditions used. 3. Such particles were obtained from seed immediately after imbibition only when 5mm-zinc sulphate was included in the medium used for extraction. 4. No polysomes were obtained from dry seed. 5. Extracts of dry seed showed limited incorporation of phenylalanine into protein. 6. Extracts of seed after imbibition showed enhanced activity in incorporation of phenylalanine amounting to 72% of the activity found in extracts of growing tissue. 7. A nuclear fraction from dry seed was able to incorporate ATP into acid-precipitable material. 8. It is concluded that the protein-synthesizing system of the dry seed is limited by the low concentration of functional polysomes.