THE RESPONSES OF ECTOHYDRIC AND ENDOHYDRIC MOSSES UNDER AMBIENT AND ENHANCED ULTRAVIOLET RADIATION, ACTA UNIVERSITATIS OULUENSIS A Sci e n t i a e Rerum Nat u r a l i u m 558

Previous reports on the effects of enhanced UV-B radiation on bryophytes have been equivocal.\nThis study shows that mosses not only respond to enhanced UV-B, but they are affected by\nchanges in ambient radiation. The studies were conducted with two model species common in\nnorthern environments; red-stemmed feather moss (Pleurozium schreberi) and juniper haircap\nmoss (Polytrichum juniperinum).\nBoth species showed high concentrations of methanol-extractable UV-absorbing compounds\n(UACs) with high spring-time and early-summer UV, whereas in P. juniperinum, the\nconcentration was affected by early-summer drought. The UACs of P. juniperinum increased\nagain towards autumn suggesting a role in winter hardening. The (spring-time) cell wall-bound\nUV screen was important to both species. The fundamental adaptation of P. juniperinum to open\nand exposed environments was reflected in relatively higher concentrations of total UACs\ncompared to P. schreberi.\nThe enhanced UV-B experiments in situ were conducted over two years in Oulu and six years\nat the FUVIRC site in Sodankylä. Some of the effects of UV-B were seen within the first years of\nthe experiments, or even within hours, while others were observed after several years. Five or six\nyears of enhanced UV-B treatment increased the methanol-extractable UACs of P. schreberi and\ndecreased the green shoot growth of P. juniperinum. The immediate light environment was\nproposed to have an impact on the varying UAC concentrations. Some mitigating effects of UVA\nwere observed as well.\nOff-site measured, reconstructed and modelled UV radiation data was used for comparisons of\nlight environment in situ, or when performing a reconstructive research with historical samples.\nThe environmental sample banks can provide a useful tool to study past environmental conditions,\nand even reconstruct past radiation levels.\nIt was shown in this study that UACs in P. schreberi and P. juniperinum have fundamental\nroles as UV-B screens in the cell walls, but there is also a variable response with the soluble\nfraction that reacts and adapts to the changes in UV radiation. The responses to increasing UV-B\nradiation vary in magnitude and in time. As P. schreberi and P. juniperinum possess circumboreal\nand cosmopolitan distributions, the effects of UV-B on these species and consequently on\necosystems has a broad application.

ISBN-10:
978-951-42-6232-6
Kieli:
eng.
Sivumäärä:
134 s.
Tekijät:
Lappalainen Niina
Tuotekoodi 013986
20,00 €