LOBLOLLY-PINE SEED DORMANCY .1. THE RELATIONSHIP BETWEEN PROTEIN-SYNTHESIS AND THE LOSS OF DORMANCY

Embryos from the mature unstratified loblolly pine (Pinus taeda L.) se eds used in this study were nondormant; however, they failed to germin ate in situ because of constraints imposed by the surrounding tissues. During a stratification period of 35 days of moist chilling at 2-degr ees-C, seed germinability increased from 19 to 76%. The total lipid co ntent of the megagametophyte did not change during stratification, whe reas the total protein content of both megagametophyte and embryo was more variable. The rate of synthesis of buffer soluble proteins in the se two tissues increased and electrophoretic analysis showed that whil e similar proteins were synthesized during the stratification period, changes in the patterns of synthesis of some proteins did occur. In bo th the embryo and megagametophyte the synthesis of a set of proteins w ith molecular masses below 46 kDa decreased markedly after 14 days of chilling (DOC). In the mega-gametophyte, the synthesis of a more diver se set of proteins with molecular masses ranging from 16 to 78 kDa inc reased after 14 DOC. It is noteworthy that these changes in the patter ns of protein synthesis coincided with the greatest relative increase in seed germinability of 35%.