Photosynthesis and Respiration of Three Mosses at Winter Low Temperatures
1971; American Bryological and Lichenological Society; Volume: 74; Issue: 1 Linguagem: Inglês
10.2307/3241751
ISSN1938-4378
Autores Tópico(s)Botany and Plant Ecology Studies
ResumoThe intensities of photosynthesis and respiration of three montane mosses were determined at winter low temperatures. The experiments were carried out under outdoor light and at air temperature, the exposure lasting 4-5 hours. The lowest temperature for CO, assimilation in Brachythecium geheebii and Camptothecium philippeanum was -90C; for Isothecium viviparum it was about -80C. In the dark respiration also occurred at -14?C. The minimum temperatures for CO, assimilation by the tested mosses in winter are somewhat lower than those for evergreen trees and nearer to the minimum temperatures for lichens. The gas exchange for the mosses at winter low temperatures is rather little known. The investigations are more advanced for lichens, which live under nearly similar conditions as the mosses. Stilfelt (1937) found that mosses can assimilate CO2 at -1C. Romose (1940) found no important changes in the photosynthetic annual course for Homalothecium. For some forest epiphytic moss associations, Miyata and Hosokawa (1961) ascertained, the highest photosynthetic rate is in August and the lowest at the end of April. Rastorfer and Higinbotham (1968) found that gametophytes of Bryum sandbergii still have the capacity to respire and to photosynthesize at -5?C. Atanasiu (1969b) found that in some montane mosses photosynthesis and respiration are somewhat increased in autumn but diminished in winter and reach the lowest level in February; they again increase towards spring. I present here my investigations on CO2 assimilation and respiration of three montane mosses at winter low temperatures. MATERIALS AND METHODS Gametophytes of Brachythecium geheebii Mild. and Camptothecium philippeanum (Spruce:) Bry. eur. were collected in the last month of autumn in Romania at Poiana Stinii, and Isothecium viviparum (Neck.) Lind. at Valea Pelesului at the same time. Poiana Stinii is situated at 1,450 m in the mid-montane belt in a mixed forest of spruce, fir, and beech. The Valea Pelesului, along the brook of Peles, is at 700-1,370 m in the lower montane belt; it has beech forests. The plants were kept on trays of sand and were exposed to the northeast on the terrace of the Plant Physiology Laboratory in Bucharest. The terrace is on the same floor as the laboratory. The mosses were thus kept outdoors during the winter of 1968-69 under natural conditions of temperature and light. During November and the first days of December, the plants were watered almost every day; the watering was stopped as soon as night frost and freezing 1 University of Bucharest, Department of Plant Physiology, Faculty of Biology, Aleea Portocalilor 1, Bucharest 15, Romania. This content downloaded from 157.55.39.157 on Tue, 17 May 2016 04:54:16 UTC All use subject to http://about.jstor.org/terms 24 THE BRYOLOGIST [Volume 74 Ltght /ntensty (/ui) IOOo[ siloooo 20001 /7 /'. 00 JO 05 fO2
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