Photoinhibition of net photosynthesis in Stereocaulon virgatum and S. tomentosum, a tropical–temperate comparison

Abstract

COXSON, D. 1987. Photoinhibition of net photosynthesis in Stereocaulon virgaturn and S. tom en to sun^, a tropical -temperate comparison. Can. J. Bot. 65: 1707 -1715.Stereocaulon tomentosum Fr., collected in pine -lichen woodlands of southwestern Alberta, Canada, and S. virgaturn Ach., collected from recent lahar flows on La Soufrikre, Guadeloupe (French West Indies), were examined for their response of net photosynthesis and respiration to brief periods of high light exposure at temperatures ranging from 10 to 40°C. In each species, a 30-min exposure period to photon flux densities of 1500 pmol . m-,. s-' resulted in a significant reduction of subsequently measured rates of net photosynthetic CO, uptake in those treatment groups which had been held at temperatures at or-above 30°C. These results suggest an altered stability of interactions between light and dark reactions of net photosynthesis at higher temperatures. They also point to the need for close monitoring of field microclimatic conditions during periods when hydrated lichen thalli are exposed to full sun conditions. Selective pressures imposed on hydrated lichen thalli during these periods of insolation shock may well prove of much greater importance in the shaping of net photosynthetic response patterns than has previously been recognized and may account for many of the previously observed disparities between those temperatures prevailing during typical periods of thallus hydration (i.e., under overcast conditions) and those at which maximal rates of net photosynthetic uptake are seen (often a full 10 to 15°C higher). These interactions appear equally important to lichens of tropical origins and to those of north temperate habitats and suggest common evolutionary drives on thermal acclimation in both environments. COXSON, D. 1987. Photoinhibition of net photosynthesis in Stereocaulon virgatum and S. tomentosum, a tropical-temperate comparison. Can. J. Bot. 65 : 1707-1715.Stereocaulon tomentosurn Fr., rCcoltC dans un boisC de pin-lichen du sud-ouest de l'Alberta, Canada, et S. virgaturn Ach., rCcoltC dans des lahars rCcents de La Soufrikre, Guadeloupe, ont Ct C examinks quant aux rkponses de leur photosynthkse nette et de leur respiration B de brkves pCriodes d'exposition h une lumikre intense, h des tempCratures s'kchelonnant de 10 h 40°C.Chez chaque espkce, une pCriode de 30 min d'exposition B des densites de flux photonique de 1500 pmol . m-,. s" rCsulte en une reduction significative des taux d'absorption de CO, chez les groupes de traitements qui ont Ct C maintenus B des tempCratures de 30°C ou plus. Ces rksultats suggkrent une stabilitk modifike des interactions entre les rkactions lumineuses et sombres de la photosynthkse nette aux tempCratures ClevCes. 11s indiquent aussi le besoin d'une surveillance Ctroite des conditions microclimatiques au champ durant les pCriodes 013 les thalles de lichen sont exposCs B des conditions de plein soleil. Les pressions de selection imposCes aux thalles hydratCs de lichen durant ces pCriodes de choc d'insolati...

Patterns of CO2gas-exchange and thallus water content in Arctic lichens along a ridge profile near Ny Ålesund, Svalbard

“…800 pmol m-2s-', Schroeter (I 991) 750 pmol m-2s-'). Coxson (1987), however, found photoinhibition in some Stereocaulon-species at PAR of 1500 prnol m-2s-1 and temperatures of 30°C or higher. For higher plants, photoinhibition induced by high temperatures is also reported (see review by Ludlow 1987).…”

Changes in in vivo chlorophyll fluorescence quenching in lichen thalli as a function of water content and suggestion of zeaxanthin‐associated photoprotection

“…Exposure to actinic when light absorption exceeds photochemical utilization light at low RWC causes a pronounced increase in NPQ. has been well documented for a variety of plants includ-At very low RWC it is difficult to estimate accurately the ing lichens (Coxon 1987, Demmig-Adams et al 1990 Physiol. Plant.…”

Effect of high light on the efficiency of photochemical energy conversion in a variety of lichen species with green and blue-green phycobionts

“…1970;Coxson 1987a;Rundel 1988). We have therefore examined the response of lichens to high light not only in the fully hydrated state, but also in thalli which were allowed to desiccate during an exposure to high light, and in thalli which were desiccated prior to exposure to high light.…”