Flowering biology of Pulmonaria obscura (Boraginaceae) in Moscow region

Abstract

Background. Pulmonaria obscura Dumort. (Suffolk lungwort) is a perennial herbaceous short-rhizome polycarpic plant. Mentions of flowering and pollination characteristics in P. obscura are scarcely found in the literature. Materials and methods. Observations were made in the natural conditions of the Moscow region from 2020 to 2022 by generally accepted methods. Results. P. obscura has two types of flowers, with short and long styles (thrum and pin, respectively), located on different individuals and distinguished by a number of parameters. P. obscura is an obligate xenogamous species: the pollen/ovary ratio is 8,273±196 on average in thrum flowers and 12,964±202 in pin flowers. Both types of flowers are adichogamous, open synchronously throughout the daylight hours, and bloom for 5–6 days. There are three types of inflorescences: dichasium of cincinni, multilayered dichasium of cincinni, or closed thyrses. The structural unit of the inflorescences is a scorpioid cyme. Conclusions. Efficient cross-pollination in P. obscura is reached by the presence of heterostyly, the synchronous rhythm of thrum and pin flowering, the formation of a large number of pollen grains in both types of flowers, and by self-incompatibility.

Keywords

• pulmonaria obscura
• flowering biology
• heterostyly