STRUCTURAL AND BIOCHEMICAL-CHANGES IN LOBLOLLY-PINE (PINUS-TAEDA L.) SEEDS DURING GERMINATION AND EARLY-SEEDLING GROWTH - I - STORAGE PROTEIN RESERVES

Quantitative and qualitative changes in the storage proteins of loblol ly pine (Pinus taeda L.) seeds were followed during germination and ea rly-seedling growth and were correlated with light-microscopic observa tions. In both the megagametophyte and the embryo, the cells of tissue s from fully stratified seeds appeared very similar to the cells of ti ssues from mature desiccated seeds. A change in the appearance of prot ein vacuoles. resulting from the hydrolysis of storage proteins, occur red in the seedling prior to the completion of germination (denoted by radicle emergence from the seed coat) and continued during early-seed ling growth. Within the seedling, storage proteins were mobilized more rapidly in the root pole, including the hypocotyl and radicle, than i n the shoot pole, including the cotyledonary whorl, and shoot apex or epicotyl. In both parts of the seedling, protein hydrolysis was first observed in the procambial and epidermal tissue. In contrast to the se edling, changes in the appearance of protein vacuoles were not evident in the megagametophyte until after germination was completed. Changes in protein vacuoles in the megagametophyte occurred in two directiona l waves, relative to corrosion cavity proximity.