Anatomical and palynological peculiarities of rare species Hyacinthella atropatana (Hyacinthaceae) in Armenia

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Hyacinthella atropatana (Hyacinthaceae) is endemic to South Transcaucasia and is also listed in the Red Book of Plants of Armenia under the EN (Endangered) category. There are three known locations of this species, namely the Darelegis and Meghri floristic regions (Armenia) and Nakhchivan (Azerbaijan). The comparative anatomical analysis of H. atropatana specimens from both Armenian populations was conducted for the first time. The results revealed no anatomical differences between the examined specimens. The observed anatomical features, including the mechanical tissue in the scape and palisade tissue in the leaf, underscore the species’ xerophilic adaptations. Our research contributes also novel quantitative data to supplement existing literature. An evaluation of the species’ anatomical traits in relation to other investigated Hyacinthella and Scilla species substantiates H. atropatana’s closest structural similarity to the genus Hyacinthella, particularly regarding scape and leaf anatomy. At the same time, H. atropatana was distinguished from the representatives of both genera by having the smallest number of vascular bundles in both the scape and the leaf, as well as a smaller number of cortex layers in the scape. The data obtained confirmed the previous opinion on the uniqueness of this species. A comprehensive study of the pollen characteristics of H. atropatana was conducted also for the first time. It revealed a noticeable palynomorphological similarity between the two Armenian populations, as well as between samples collected in Armenia and Nakhchivan (Azerbaijan), which may be attributed to the considerable resemblance of their habitats. Additionally, our research established that within the Hyacinthella genus, H. atropatana is distinctive both in the size of pollen grains (somewhat larger than those noted for other studied species) and the uniqueness of pollen exine ornamentation. The data received support the previously proposed assumption about some isolation of this species within the Hyacinthella genus and its placement in a separate section, Atropatana.