A comparison of the stomatal parameters of Sesuvium portulacastrum (L.) L. (Aizoaceae) was carried out between samples collected from a naturalizing population in Egypt and the same plants after six months of cultivation in the greenhouse of the Tsitsin Main Botanical Garden of the Russian Academy of Sciences. The stomatal apparatus was studied using the Polacci lacquer replica method and characterized by 21 quantitative traits. S. portulacastrum leaves are amphistomatic, with a paracytic stomata. The total transpiration area did not change significantly over six months of cultivation, but a downward trend in stomatal area was observed. The ratio of stomata on the upper, adaxial side of the leaf to the total number of stomata decreased by half due to decreased solar radiation. At the same time, the number of stomata on the abaxial side of the leaf doubled. Thus, the beginning of adaptation of the stomatal apparatus of Sesuvium portulacastrum to greenhouse conditions is manifested by a decrease in the number of stomata on the adaxial side of the leaf blade and a distinct trend toward decreased stomatal area.

Keywords: adaptation, Egypt, greenhouse, naturalization, Sesuvium portulacastrum, stomata