Anatomical structure of the calyx transverse section of some species of the Hedysarum L. genus (Fabaceae) from Central Asia

This research investigates the anatomical structure of the calyx transverse section of 11 species of the Hedysarum genus from Central Asia. The analysis revealed that all species exhibit a more or less smooth or slightly convoluted upper surface and a lower surface with varying degrees of tuberculation. Regarding the mesophyll structure of the calyx, the studied species are mainly divided into two groups: in H. pumilum, H. severtzovii, H. micropterum, and H. wrightianum, the mesophyll is differentiated into lower palisade and upper spongy layers, which is considered an adaptive and progressive feature for the calyx; in other species, an undifferentiated mesophyll is observed, regarded as a primitive trait. Furthermore, the formation of large and giant idioblasts is characteristic of all studied species, located on the lower side of the calyx (directly beneath the lower epidermis), along with a 2-4-layered chlorenchyma beneath the upper epidermis, representing adaptive features.