Pigment formation & photosynthesis in dormant lettuce seeds

Abstract

Lettuce seeds prevented from germinating by maleic hydrazide can develop chloroplasts in an internal sector of cotyledons exposed to light. These chloroplasts appear identical under the microscope with those normally found in expanded cotyledons of germinated seedlings. Chlorophyll and carotenoid-like pigments can be extracted from such seeds. These seeds perform a light-dependent fixation of C14 -bicarbonate, with radioactivity appearing in sucrose, sugar phosphates, and amino and keto acids. Similarly treated dark-imbibed control seeds do not develop chlorophyll or the capacity for photosynthesis. These findings furnish an instance of tissue differentiation in dormant seeds that is both anatomical and physiological.