Protein mobilization from cotyledons of de-shooted pea seedlings
The role and regulation of proteolytic enzymes in protein mobilization from seed storage tissues is not fully understood. Surgical removal of the shoots of 5-day-old pea seedlings was found to double the longevity of the cotyledons remaining attached to the roots. Despite the healthy appearance of these cotyledons (green, turgid), their protein content decreased rapidly. After 14 days of seedling growth, the protein level decreased, but remained about 3 to 4 times greater than the amount present in normally senescing cotyledons of untreated seedlings. Specific differences in the cotyledonary albumin and globulin complement of 14-day-old de-shooted and control seedlings were revealed by electrophoresis. Proteolytic (casein degrading) activity was present in dry and senescing cotyledons. The need to purify this enzyme prior to a further characterization of its role in the senescence of cotyledons was demonstrated.