Morphological characteristics of pollen and cypsela in the genus Rhaponticum (Asteraceae) from Turkey and their systematic significance

Abstract

Pollen and cypsela morphology of four species of the genus Rhaponticum (Asteraceae) distributed in Turkey were investigated and compared utilizing light microscopy and scanning electron microscopy to identify these characteristics and to evaluate the diagnostic value of them for contribution to the systematics of the Turkish Rhaponticum. The pollen grains of Rhaponticum are radially symmetrical and isopolar. Their shape is prolate-spheroidal and oblate-spheroidal, with the polar axis ranging from 32 to 56.64 μm and the equatorial axis ranging from 31.92 to 56.64 μm. The aperture type is usually trizonocolporate, and rarely tetracolporate. Exine sculpturing can be divided into two types, namely microechinate and echinate. The cypselas are obovoid or narrowly obovoid in shape and dark brown with cream at the base, brown or dark yellow-green in color. The size of the cypselas range between 3.19–11 mm in length and 1.4–4.5 mm in width. The pappus shows variation in type and status: barbellate, scabrose and barbellate at apex, plumose or only scabrose and persistent or deciduous. Cluster analysis and principal component analysis revealed that especially pollen size, pollen shape, exine ornamentation, cypsela length and pappus type are significant variables for separating species in the taxonomy of the genus.

Keywords:

• Fruit
• numerical analysis
• palynology
• Rhaponticum
• SEM

Acknowledgments

I am grateful to the curators of herbaria GAZI and HUB who allowed me to study their Rhaponticum material.

Disclosure statement

No potential conflict of interest was reported by the author(s).