Germination Patterns of Dimorphic Achenes in Launaea nudicaulis (Asteraceae) Growing in Desert Environments

Abstract

Launaea nudicaulis (Asteraceae) produces two morphologically distinct types of achenes (whitish brown and black) in a single capitulum. All L. nudicaulis achenes have a pappus and pappi were removed artificially in this study for experimental purposes. The germination of achenes of both colours, with and without pappi, under various temperature regimes and illumination conditions was tested. Different coloured achenes showed differences in their mass and germination behavior. Whitish brown achenes (with and without pappi) displayed greater germination than black ones. Whitish brown achenes without pappi generally displayed greater germination than achenes with pappi. Continuous darkness enhanced germination, regardless of the presence of pappi, indicating that L. nudicaulis seeds are negatively photoblastic.