Polygonum schisckinii

Yurtseva, Olga V., Severova, Elena E., Deviatov, Andrey G., V. Olonova, Marina & Samigullin, Tahir H., 2021, Polygonum schischkinii is a member of Atraphaxis (Polygonaceae, Polygoneae): evidences from morphological and molecular analyses, Phytotaxa 491 (3), pp. 193-216 : 209

Morphology of Polygonum schisckinii and related taxa of Polygoneae

Polygonum schischkinii displays the perianth with five equal-sized tepals, which is common in the tribe Polygoneae , occurring in the genera Polygonum , Bactria , Caelestium , Persepolium and some species of Atraphaxis : A. toktogulica (Lazkov in Lazkov & Sultanova 2002: 96) T.M.Schust. & Reveal ( Schuster et al. 2011b: 1663), A. atraphaxiformis ( Botschantzev 1965: 270) T.M.Schust. & Reveal ( Schuster et al. 2011b: 1663) , and A. tortuosa Losina-Losinskaja (1927: 44) . All the listed taxa, for exception of Polygonum , have papillate edges of the tepals, which were found also in Polygonum schischkinii.

Similarly to Bactria , Caelestium , Persepolium and Atraphaxis , Polygonum schischkinii has a receptacle formed by fused basal parts of the tepals and lined with nectar secreating tissue below and around the bases of the filaments ( Yurtseva et al. 2017, 2019). This species has also the same irregular striation of epidermal cells covering the tepals abaxially, which is present in some species belonging to Atraphaxis , Bactria , and Caelestium . Persepolium has a perianth shortly velutinous-puberulent outside ( Yurtseva et al. 2017). Most members of Atraphaxis have a specialized perianth with accrescent inner tepals and differ with more subtle and fine irregular cuticular striation of the tepal cells ( Hong et al. 1998, Yurtseva et al. 2017).

Pollen morphology clearly differentiates Polygonum schischkinii from all other members of Polygonum s.l. Polygonum s.str. [which includes P. sect. Polygonum and P. sect. Tephis, sensu Yurtseva & Mavrodiev (2019) ] has psilate, microspinulose sporoderm ornamentation (pollen Avicularia-type sensu Hedberg 1946), or psilate around the colpi and verrucate at the poles [pollen Pseudomollia-type sensu Hong in Hong et al. (2005) detected in P. molliiforme and P. bornmuelleri Litvinov (1910:82) ]. The North-American Duravia and Polygonella have the following distinct sporoderm ornamentation ( Hong et al. 2005): semitectate-reticulate at mesocolpia, rugulate/reticulate or sometimes foveolate with microspinules around ectoapatures (pollen Duravia-type sensu Hedberg1946).

Microreticulate-foveolate sporoderm ornamentation found in Polygonum schischkinii put it close to Bactria ovczinnikovii , the genus Caelestium , and some species of Persepolium (see Yurtseva et al. 2016a, 2017, 2019). Atraphaxis toktogulica has the sporoderm ornamentation transitional from reticulate-perforate to striate-perforate. The remaining Atraphaxis species have striate-perforate to striate-foveolate sporoderm ornamentation ( Hong 1995, Yurtseva et al. 2014, Yurtseva et al. 2016a). Thus, despite Polygonum schischkinii shares some traits with members of Polygonum s.l., the papillate tepal edges and microreticulate-foveolate sporoderm ornamentation put it into the clade “ Atraphaxis s.l. ” ( Atraphaxis s.str., Persepolium , Bactria , and Caelestium ).

The morphology of ocreas and ocreolas definitely puts Polygonum schischkinii in the genus Atraphaxis . The ocreas of P. schischkinii are lanceolate-tubular and split in two lateral lanceolate lacinulas and a serrate-incised middle lobula, which is characteristic of Atraphaxis s. str. ( Yurtseva et al. 2017). Bactria and Caelestium have bilacerate ocreas without middle lobula. Persepolium has truncate-tubular or lanceolate-tubular ocreas 3–10 mm long, without visible veins ( P. spinosum ), with two veins ( P. dumosum , P. salicornioides ), or 4–6 veins ( P. aridum ), later split into 2–4 lacinulas.

In addition, the morphology of the shoots, leaf blades, inflorescences, perianth, fruit, as well as fruit anatomy of Polygonum schischkinii showed great similarity with some species of Atraphaxis , what makes it possible to classify P. schischkinii as Atraphaxis s.str.