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PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Author(s) -
KERSHAW K. A.,
MACFARLANE J. D.
Publication year - 1982
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1982.tb03281.x
Subject(s) - thallus , nitrogenase , lichen , photosynthesis , deserts and xeric shrublands , acclimatization , botany , biology , ecology , dew , horticulture , habitat , nitrogen fixation , physics , meteorology , genetics , bacteria , condensation
S ummary The seasonal response matrix of gas exchange and nitrogenase activity in Collema furfuraceum is presented for a number of factorial combinations of light, thallus temperature (5, 15 , 25 and 30 to 35 °C) and thallus water content, throughout the year. The results indicate C. furfuraceum is adapted both to the relatively xeric environment of its cortieolous habitat as well as to the low temperatures experienced in its low‐arctic environment. Of particular interest is the absence of a summer thermal stress response, which eliminates or severely reduces nitrogenase activity during the summer months in some lichens growing in more southerly localities. Equally, ambient temperatures during the winter, which can drop to minus 41 °C, do not affect nitrogenase activity and confirm the resistance of the nitrogenase enzymes in the intact thallus, to low temperatures. There is a remarkable degree of uniformity in the net photosynthetic response matrix, at most light levels, at all experimental temperatures and at all times of the year. The total absence of seasonal photosynthetic acclimation as well as the seasonal constancy of photosynthetic capacity is discussed in terms of differential strategies in contrasting environments.