Contribution of cotyledons to seedling dry weight and development in Medicago falcata L.

摘要

Abstract Three experiments are reported, two of which involved cotyledon excision, to elucidate seedling developmental strategy of a North China rangeland legume, Medicago falcata. Early loss of cotyledons was fatal, with data indicating a possible hormonal‐type signal from cotyledons to initiate first leaf expansion. Cotyledons made a substantive photosynthetic contribution for some 28 days from imbibition, but high seedling relative growth rates were not observed until after first leaf expansion. On removal of both cotyledons at 7 days, seedlings responded with an increase in shoot:root dry weight ratio; on removal of one cotyledon only at this time a transitory shift of allocation from shoot to root was observed until normal ontogeny was restored. Removal of one or both cotyledons at 14 days delayed seedling development but did not change seedling ontogeny. This study was part of a series of experiments to better understand the autecology of M. falcata.