Achenes of Tragopogon dubius have previously been described as dimorphic with respect to size and colour. In this investigation we found that there is a continuum of weight change from lighter central achenes to the heavier peripheral achenes. The main component of change is the pericarp. Outer achenes may also contain larger quantities of phenolic compounds than inner achenes. The differences in mass, morphology, and chemical characteristics may be significant enough to result in differences in germination behaviour. No such differences were seen in standard laboratory germination tests, though in a greenhouse experiment, seedlings from peripheral achenes emerged later and were larger and taller than seedlings from central achenes. The presence of phenolic compounds in the fruits of T. dubius suggests that the peripheral morphs may retain viability longer in the seed bank. Key words: somatic polymorphism, heteromorphism, germination, emergence, Tragopogon.
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