The Dual Functions of the Cotyledons of Acacia iteaphylla F. Muell. (Mimosoideae)

Abstract

The storage of reserve materials in the seeds of Acacia iteaphylla F. Muell. occurs mainly in the cotyledons of the embryo which occupy the major part of the seed volume. After germination, the mobilization of reserve proteins (albumins and globulins) occurs in two distinct phases: an initial slow phase of about 2 weeks, during which a decline of c. 70% in cotyledon dry matter occurs, followed by a rapid phase in the third week, accompanying the development of photosynthetic capacity in the cotyledons and the initial expansion of the primary leaf. The possession of both storage and photosynthetic functions by the cotyledons in Acacia places the Mimosoideae in an intermediate position with respect to the Caesalpinioideae (seeds with endosperm, cotyledons leaf-like) and the Lotoideae (Papilionoideae), with many representatives showing cotyledons adapted entirely for storage.