New Zealand Journal of Agricultural Research abstracts

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

Hongxiang Zhang¹

Yi Wu¹

Cory Matthew²

Daowei Zhou^1,*

Ping Wang¹

¹Institute of Grassland Science
Northeast Normal University; Key Laboratory of Vegetation Ecology
Ministry of Education
Jilin Province

130024, China

²Institute of Natural Resources
Massey University
Private Bag 11222
Palmerston North 4442, New Zealand

^*Author for correspondence: choudaowei@yahoo.com.cn

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.

Keywords cotyledon removal; dry weight; Medicago falcata; photosynthesis; relative growth rate; seedling development strategy

A07170; Online publication date 6 June 2008; Received 20 August 2007; accepted 31 March 2008

New Zealand Journal of Agricultural Research, 2008, Vol. 51: 107–114
0028–8233/08/5102–0107 © The Royal Society of New Zealand 2008

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