Physiology of Pea Fruits

Abstract

Changes in UDPG pyrophosphorylase and ADPG pyrophosphorylase and a number of other constituents were followed during the growth of the pea seed. At all stages of development of the seed UDPG pyrophosphorylase activity was much higher than ADPG pyrophosphorylase activity. During the period of starch formation there was a similarity in the changes in starch and UDPG pyrophosphory-lase and ADPG pyrophosphorylase. The maximum rate of starch synthesis coincided with the maximum activity of ADPG pyrophosphorylase. The results are consistent with the biosynthesis of starch from ADPG but do not preclude the participation of UDPG as substrate in this process. It is suggested that UDPG pyrophosphorylase may provide a source of glucose I-phosphate from sucrose for ADPG formation.