Lectins and storage proteins from pea (Pisum sativwn) and other Leguminosae seeds interact in vitro. In order to evaluate whether this relationship may be important also in vivo, the time course of biosynthesis of these proteins in developing pea seeds was followed. The proteins appear in the following temporal order:vicilin -lectin -convicilin -legumin. The time course of protein synthesis was also followed by the subcellular morphological changes occurring simultaneously. The appearance of vicilin coincides with the formation of regularly shaped protein globules within the vacuole. Immediately after the start of lectin synthesis, these globules flatten and begin to adhere to the inner membrane surface of the vacuole. Legumin appears at a time when the vacuoles already have largely disappeared in favour of smaller vesicles which eventually develop into protein bodies.These results together with previous findings are consistent with the view that one of the biological functions of the lectin may consist in serving as a link between vicilin and the inner face of the vacuole membrane.

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