EFFECTS OF A SIMULATED ACID RAIN EPISODE ON PHOTOSYNTHESIS AND RECOVERY IN THE CARIBOU‐FORAGE LICHENS, CLADINA STELLARIS (OPIZ.) BRODO AND CLADINA RANGIFERINA (L.) WIGG.

Abstract

SUMMARYThe effect of simulated acid rain on net photosynthesis of two common boreal forest lichens, Cladina stellaris and Cladina rangiferina, was investigated. Repeated measurements of net photosynthetic rate (NPR) were conducted on podetial tips over a week-long period to assess both immediate response to an acid spray treatment (2:1 H2SO4:HNO3; pH range 2-5 to 3-5) and subsequent photosynthetic recovery after the solution of artificial rain had been rinsed out of the cells. A control group, which was treated with pH 56 episodes, was used to monitor natural fluctuations in NPR over time in a laboratory environment. Although lowered photosynthetic rates were observed for both species immediately following a low pH treatment, differences between groups were not significant. Three days following treatment, howeverŝ ignificant decreases in photosynthesis of up to 40 % of pretreatment values were found for pH 2-5 and 3-0-sprayed C stellaris, and a decline in NPR of 25 % was recorded for pH 3-0-treated C rangiferina. Six days after the simulated rain episode, a 20% recovery of photosynthesis had occurred in pH 2 5-treated C. stellaris, while pH 3 0-sprayed C. rangiferina underwent a 20 % stimulation of NPR compared to the pretreatment value. In spite of the demonstrated ability to recover partially following a single low pH event, it is hypothesized that even temporary declines in NPR could restrict growth potential and biomass accumulation of boreal cyptogamic species which have a short growing season and photosynthesize only when moisture is available. Results of the study indicate that C. stellaris is more sensitive to single low pH events than is C. rangiferina.

The influence of air pollution on the concentration of mineral elements, on the spectral reflectance response and on the production of stress–ethylene in the lichen Ramalina duriaei

“…In lichens, the impact of acid rain on the physiology of the thallus is well known (e.g. Sigal & Johnston, 1986 a, b;Scott & Hutchinson, 1987;Gunther, 1988;Scott, Hutchinson & Feth, 1989;Hallingback & Kellner, 1992) as well as the capability of lichens to absorb and accumulate heavy metals which is greater than that of higher plants (e.g. James, 1973 ;Brown & Beckett, 1985;Puckett, 1988;Brown, 1991;Garty, 1992Garty, , 1993.…”

Cation ratios inCladonia portentosaas indices of precipitation acidity in the British Isles

“…Scott, Hutchinson & Feth, 1989;Farmer, Bates & Bell, 1991), (ii) impaired physiological activity-(e.g. Sigal & Johnston, 1986;Scott & Hutchinson, 1987;Gunther, 1988;Roy-Arcand, Delisle & Briere, 1989;Hallingback & Kellner, 1992;Kytoviita & Crittenden, 1994) and (iii) reduced growth rates (e.g. Lechowicz, 1987;Scott & Hutchinson, 1990;Hallingback & Kellner, 1992).…”

Ethylene produced by the lichen Cladina stellaris exposed to sulphur and heavy‐metal‐containing solutions under acidic conditions

“…Acidic rain possibly accounts for the disappearance of certain lichen species (Gilbert, 1986 ;Hallingba$ ck & Kellner, 1992 ;Gauslaa, 1995) or for their being severely damaged and endangered in industrialized countries (Mahaney et al, 1995). Many publications dealt with the effect of simulated acidic rain on physiological parameters of lichens such as photosynthesis (Lechowicz, 1982 ;Sigal & Johnston, 1986 a, b ;Scott & Hutchinson, 1987 ;, nitrogenase activity (Fritz-Sheridan, 1985 ;Gunther, 1988 ;Hallingba$ ck & Kellner, 1992 ;Kyto$ viita & Crittenden, 1994) and growth (Scott, Hutchinson & Feth, 1989 b).…”