Photosynthetic contribution of cotyledons to early seedling development in Cynoglossum divaricatum and Amaranthus retroflexus

Abstract

This study evaluated cotyledon contribution to seedling development in a small-seeded species (Cynoglossum divaricatum, seed weight 8.51 mg) and a very small seeded species (Amaranthus retroflexus, seed weight 0.46 mg), focusing on the balance between the reserve storage role and the photosynthetic role of cotyledons. The data provide insight complementary to that from earlier studies which have not generally included seeds as small as those of A. retroflexus. The data highlight the way in which almost total reliance on the photosynthetic role of cotyledons in small-seeded species can achieve a very high relative growth rate during early seedling development, and raise the possibility that quantitative determ ination of the ratio between the photosynthetic contribution of cotyledons to seedling development and total (photosynthetic plus reserve) contribution may provide a useful indicator of species competitive strategy and fitness for different habitats. © 2008 Taylor & Francis Group, LLC.