Dynamics of flower and pod production in annual medics (Medicago spp.). I. spaced plants

Abstract

Two experiments were conducted in Syria to examine flower production in annual medics. Flowers and pods of seven species were monitored throughout the flowering period in Experiment 1 and the relationships among 13 flowering attributes were investigated for 16 species in Experiment 2. Between 34% (M. rigidula) and 8 1% (M. minima) of flowers survived to maturity in Experiment 1 and between 27% (M. blancheana) and 93% (M. radiata) survived in Experiment 2. Flower and pod production and flower survival in most species increased until about node 7 and decreased thereafter. Seed size was greatest in pods produced before nodes 2-7; the seed in late-produced pods was only 50% as heavy as early-produced seeds. Seed number per pod was almost constant, indicating that ovule abortion was rare. Cluster and regression analysis suggested that greater flower retention was associated with low number of seeds per plants, small seeds, and small pods, and the data support the hypothesis that flower survival is determined by the potential mass of pods (pod mass by flower number) at each raceme. The ecological and agronomic significance of flower shedding and seed size is discussed, and it is suggested that more attention should be paid to the characteristics of successful ecotypes in a given area, when selecting cultivars for that area.