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Abstract
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Background: The macro/micro-morphology of nutlets in 11 species (and 22 accessions) of the Boraginaceae family
was investigated using stereomicroscope and scanning electron microscopy to evaluate the taxonomic relevance of
the traits. To evaluate the phylogenetic significance of the character evolution, phylogenetic analysis was carried out
by comparing available DNA sequence data from GenBank with selected original nutlet data.
Results: The Rochelieae nutlets’ shape varied from ovoid (ovoid, ovoid-triangular, and ovoid-rectangular) to pyramid.
Six major patterns were recognized based on the nutlet ultrastructure characters. Rocheliae is characterized by a
transition from “without appendage” to “with tubercles and prickles” on the nutlet disk, and also via a shift from “lack of
prickles” to “glossy prickles”.
Conclusions: The results show that the nutlet ultrastructure pattern of Rochelieae is systematically informative at the
genus level, but not at the species level. Findings demonstrated that glochid is not an ancestral trait but is a synapomorphy
and the transition to this trait occurred in the genus Lappula. The close boundary of nutlet microstructures
between L. barbata and L. microcarpa has been discussed.
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