Effect of Anatomical Structure on the Buoyancy of Achenes of Two Subspecies of Bolboschoenus maritimus

• Published in: Folia geobotanica & phytotaxonomica Vol. 32; no. 4; pp. 377 - 390
• Main Authors: Zdenka Hroudová, Lenka Moravcová, Petr Zákravský
• Format: Journal Article
• Language: English
• Published: Institute of Botany, Academy of Sciences of the Czech Republic 01-01-1997
• Subjects: Achenes; Anatomy; Body tissues; Buoyancy; Endocarp; Exocarp; Fruits; Mesocarp; Pericarp; Plants
• ISSN: 0015-5551; 1573-1170
• DOI: 10.1007/BF02821943

Differences between two subspecies of Bolboschoenus maritimus (L.) Palla (= Scirpus maritimus L.) in different habitats (littoral and terrestrial) are partly due to variations in the buoyancy of their achenes, caused by different anatomical structure of the fruits. This hypothesis was tested by comparing fruit buoyancy and anatomy of both subspecies at several localities. Plants were sampled from Bolboschoenus maritimus subsp. maritimus (plants with branched inflorescences and triangular fruits, 4 localities) and B. maritimus subsp. compactus (Hoffm.) Hejný (plants with compact inflorescences and prevailing concave fruits, 4 localities) in the Czech and Slovak Republics, and B. maritimus subsp. compactus (plants with compact inflorescences and convex fruits, 1 locality) from the coast of South Sweden. From each locality a plant with several tubers connected by rhizomes was taken and transferred into the experimental garden; from these cultivated plants (clones) mixed samples of fruits collected from each clone were used for buoyancy tests and a study of their anatomy. Fruit buoyancy was found to depend on the anatomical structure of the pericarp - the presence of aeriferous tissue in the exocarp serves as the main floating organ. This differentiated all plants studied into two groups: short-floating subsp. maritimus, with a thin or none aeriferous tissue in the exocarp, and long-floating subsp. campactus with well developed aeriferous tissue. Differences in fruit buoyancy corresponds to differences in the prevailing habitat types of both subspecies studied in the inland sites: the frequent occurrence of subsp. campactus in temporarily flooded terrestrial habitats contrasts with the prevalence of subsp. maritimus in the littoral of water bodies. This is an example of intra-specific ecological differentiation leading to differentiation in wetland communities.