Cleistogamy inCentaurea melitensis (Asteraceae): Capitulum variability and spatio-temporal development patterns

Centaurea melitensis is a cleistogamous species of Mediterranean distribution, which normally produces a wide range of capitula varying in terms of morphology, size, position in the shoot system and other aspects. For that reason, and particularly in view of the pseudanthic nature of the flower head in Asteraceae, a preliminary study to characterise cleistogamy in this species was considered of interest. Capitular heteromorphism observed inC. melitensis was confirmed by principal component analysis (PCA). The five capitulum types differentiated initial cleistogamous (iCL), intermediate cleistogamous (xCL), final cleistogamous (fCL), pseudocleistogamous (PCL) and chasmogamous (CH)] fit development patterns specific for both placement on the plant and timing. The balance between cleistogamy and chasmogamy is correlated with the final height of the plant. All these features are consistent with those reported for other cleistogamous species.