Dynamics of flower and pod production in annual medics. (Medicago spp.). II. In swards at low and high density

Abstract

Seven accessions of five annual medic species were grown in swards at low and high densities at Tel Hadya in north Syria. Flower shedding, seed size, and other components of seed yield were compared with data collected from spaced plants. Seed yield of the seven accessions, ranging from zero to 800 kg ha-1, was correlated with flowering time at high density but not at low density. Early flowering accessions of Medicago polymorpha and M. truncatula produced more seed at high density than at low density, but a late-flowering accession of M noeana failed to produce seed at high density. Flower shedding was greatest in dense swards and least in spaced plants. Shedding of the various accessions ranged from 70% to M. polymorpha at low density to 96% in M. rigidula and 100% in M. noeana at high density. Some accessions shed flowers uniformly from all nodes, but in other accessions late-produced flowers were more likely to be shed. The flower shedding observed here was less than found in many other legumes, but more than has been observed in subterranean clover. It seems unlikely that seed yield can be increased by selecting for increased flower retention, but it may be possible to increase seed numbers at the expense of seed size; this may be useful in pasturebased farming systems.