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Ten monthly samples of 33–160 plants of Phycodrys rubens (L.) Batt. collected at 2–5 m in the Dalnezelenetskaya Inlet, Murman coast of the Barents Sea, and one autumn collection of 127 plants from the Chupa Inlet, White Sea, were analysed for age structure, seasonal increment, and reproductive stage. Additional data were extracted from collections from various other localities on the Murman and White Sea coasts. The life span of Phycodrys rubens was 4 years; first and second year plants were predominant. Mean blade length increased steadily in spring, to level off in summer, and showed a second short period of increment in autumn. Mean absolute length growth was up to 48 mm year −1 in the first year, and mean absolute weight growth was up to 1.8 g year −1 in fifth year plants. Formation and maturation of tetrasporangia were observed in plants from the Murman coast during the whole year, but abundantly so by the end of summer and in autumn. Developing spermatangia and procarps, and early stages of gonimoblasts occurred in April–July. Gonimoblasts at different stages of development were found all the year round. Tetra- and carpospores were released simultaneously in great numbers in October–December. In the White Sea the timing of reproduction of Phycodrys rubens appeared to be the same. The plants started to reproduce by the end of the first year of life. The highest number of mature fertile plants was found among 1 to 2-year-old plants, while the largest surfaces of reproductive tissue occurred in 4-year-old plants. In autumn one tetrasporophyte could produce about 150000 (up to 550 000) tetraspores. One female gametophyte could produce about 49 000 (up to 120 000) carpospores. On the Murman coast, reproduction by tetraspores plays the main part. |
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