A study of the seeds and tubers of Sandersonia aurantiaca (Hook.) (2001)
AuthorsStilwell, Stephen A.show all
The major proteins of Sandersonia seeds are salt soluble globulins visible as six subunits (bands) under SDS PAGE conditions. Electrophoretic characteristics also suggest that the globulin proteins in Sandersonia seeds resemble the vicilin sub-type. The major tuber proteins are water soluble albumins consisting of 4 subunits under SDS PAGE conditions. Differences in the solubility and subunit characteristics of seed and tuber protein disproved a hypothesis that they may be related, due to a similar life cycle function. Through SDS PAGE and light microscopy (indirectly), the six seed subunits were found to form by 30 DAP, but not before 25 DAP. Between 30 and 60 DAP, the major seed proteins were found to accumulate, partially fulfilling the storage protein definition. Due to a deep dormancy mechanism, the seeds could not be germinated in significant quantities to demonstrate major protein degradation. The major seed proteins can only tentatively be defined as storage proteins. The fate of the major tuber proteins was monitored, over the first six weeks after new season planting. No difference in the four-band (SDS PAGE) pattern was noted, during this time. The major tuber proteins were then monitored at three further developmental stages. Degradation of the major tuber proteins was observed to occur at the same time as seed formation and final daughter tuber formation. The major tuber proteins fulfil the storage protein definition regarding their degradation. Accumulation of the major protein is inferred through their presence at tuber maturity. Three structural types of protein body were observed to occur. These accumulated differentially between tissues. SDS PAGE and TEM evidence indicate that the crystalloid type of protein body inclusions are absent from Sandersonia seeds, though the crystal and soft globoids are present, the former, in limited numbers, and the later in much larger numbers. Thickening of the seed endosperm cell walls was observed and attributed possible functions of desiccation resistance and/or carbohydrate storage.