Physiological‐environmental Interactions in Lichens

Abstract

SUMMARYThe seasonal changes in the ability of Cladonia rangiferina to tolerate heat stress are examined in late winter, early spring and in summer. The effects of heat stress are examined as changes in net photosynthetic and respiration rates following air-dry storage of lichen replicates at two stress temperatures, 35 and 45 °C, for 21 days. In late winter the experimental replicates show reduced net photosynthetic rates after 7 days stress treatment at 35 °C. By mid-summer this treatment has no deleterious effects and it is concluded that there is approximately a 10 °C increase in heat tolerance in Cladonia rangiferina between late winter and mid-summer.

Contrasting sensitivity to extreme winter warming events of dominant sub‐Arctic heathland bryophyte and lichen species

“…We have interpreted the reduced vitality of H. splendens as being a result of the freezing stress that they were exposed to after the warming events. However, as winter‐adapted cryptogams have reduced heat tolerance (Tegler & Kershaw 1981; Longton 1988), one may consider that the warming per se also had negative effects. There are, however, to our knowledge, no reports that might suggest that H. splendens would be less tolerant than P. aphthosa to winter heat.…”

High-light damage in air-dry thalli of the old forest lichen Lobaria pulmonaria--interactions of irradiance, exposure duration and high temperature

“…menziesii (Larson, 1989) and seasonal variations in Cladonia rangiferina ( Tegler and Kershaw, 1981) suggest Furthermore, it has been claimed that a desiccationinduced disconnection of the light-harvesting complexes that the tolerance to high temperatures is a plastic physiological character which may be important in permitting protects the photochemical apparatus against the adverse effects of high light (Sigfridsson, 1980;Bilger et al, 1989; colonization, establishment and growth of these species. This might also be the case for L. pulmonaria.…”

Seasonal Photosynthetic Capacity Changes in Lichens: A Provisional Mechanistic Interpretation

“…This has been widely documented during seasonal photosynthetic changes in desert plants (Mooney et al 1978, Armond et al 1978, Badger et al 1982. As there is already some evidence of seasonal changes to thermal stress in lichens (Tegler & Kershaw 1981) some of these earlier reports of capacity changes in lichens which occurred below light saturation and particularly at higher experimental temperatures could reflect thermal membrane responses of the light harvesting system. A re-examination of these earlier reports is accordingly now necessary.…”