Physiological‐environmental Interactions in Lichens

Coxson, Darwyn S.; Harris, Graham P.; Kershaw, K. A.

doi:10.1111/j.1469-8137.1982.tb03415.x

Cited by 18 publications

(8 citation statements)

References 16 publications

(14 reference statements)

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“…Critical values above 500% of dry weight were reported for the terrestrial Nostoc cyanophyte (Coxson et al, 1982;. Critical values above 500% of dry weight were reported for the terrestrial Nostoc cyanophyte (Coxson et al, 1982;.…”

Section: Discussionmentioning

confidence: 89%

CO2 Exchange in soil algal crusts occurring in the trachypogon savannas of the Orinoco Llanos, Venezuela

Jose

Bravo

1991

Plant Soil

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CO 2 exchange between the atmosphere and soil algal crusts of the Trachypogon savannas of the Orinoco Llanos has been analyzed using an open gas exchange system. These savannas encompass a wide range of physiognomic types, from herbaceous communities to savanna woodlands. A maximum CO 2 -2 -1 . . . . flux of 0.207 mg m s was measured in the crusts of the Guampa savannas, while m the other examined crusts (0.035-0.105 mg m -2 s-1) the flux was similar to values reported for terrestrial algae. The CO: flux data were statistically fitted to the photosynthetically active radiation by a logarithmic relationship, and the photosynthetic efficiencies of the crusts were compared. The activation energy calculated for the CO 2 fixation indicates that limitations by diffusion and photochemical processes were excluded in the Guanipa crusts (above 12 kcal mole i), whereas they were evident in the other crust studied. An optimum CO 2 incorporation as a function of the crust water potential was established and carbon gain strategies were proposed on the basis of the results and characteristics of the habitats.

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Section: Discussionmentioning

confidence: 89%

CO2 Exchange in soil algal crusts occurring in the trachypogon savannas of the Orinoco Llanos, Venezuela

Jose

Bravo

1991

Plant Soil

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“…It is not known to what extent the mycobiont is responsible for this. Respiration in lichens is generally thought to be mycobiont‐dominated but there are exceptions (Coxson et al. , 1982).…”

Section: Discussionmentioning

confidence: 99%

Photosynthesis in a sub‐Antarctic shore‐zone lichen

Smith

Gremmen²

2001

New Phytologist

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Summary• Photosynthetic responses to moisture, light, temperature, salinity and inorganic nitrogen fertilization are reported for a shore-zone lichen Turgidiusculum complicatulum (formerly Mastodia tesselata ), a possible recent introduction to subAntarctic Marion Island.• Optimum moisture contents for net photosynthesis were 225 -346% (ash free, dry mass). Net CO 2 exchange was dominated by a strong temperature dependence of respiration rate. Net photosynthetic rate responded sharply to increasing PPFD and saturated below 300 µ mol m -2 s -1 , but electron transport rate (ETR) increased up to approx. 900 µ mol m -2 s -1 PPFD suggesting that gross photosynthesis responded to light to this level. Nonphotochemical fluorescence quenching increased rapidly with PPFD up to approx. 400 µ mol m -2 s -1 and thereafter more slowly. Even at high PPFD (1050 µ mol m -2 s -1 ) most PSII centres were open.• Salinity did not significantly influence CO 2 assimilation rate; however, NH 4 NO 3 significantly depressed net photosynthesis rate at all salinities except 100% seawater. ETR and dark respiration rate were increased by NH 4 NO 3 .• The response of T. complicatulum to light and temperature enables high rates of CO 2 assimilation under the island's microclimatic regime; if sufficiently hydrated, the lichen would exhibit near maximal photosynthesis rates for approx. 75% of the photoperiod over the year.

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“…A more probable explanation for these changes in respiratory response is that an accumulation of cytoplasmic ATP (adenosine triphosphate) occurred under conditions of lower photon flux density. Under high photon flux densities the ATP levels in the phycobiont chloroplasts may rise sufficiently to reduce the demand for ATP generated by light respiration (a continuation of dark-type respiration in the light, in contrast to photorespiration), a phenomenon described for chlorophyte green algae by Bidwell (1977) and later reported by Coxson et al (1982) for both free-living and lichenized Nostoc phycobionts. Of course under conditions of high insolation and increased temperature the greater demands of photorespiration for reducing equivalents would act to reduce the cytoplasmic ATP charge and thus allow a greater role for normal respiratory activity (Kriedemann and Downton 1981).…”

Section: Discussionmentioning

confidence: 96%

“…Of course under conditions of high insolation and increased temperature the greater demands of photorespiration for reducing equivalents would act to reduce the cytoplasmic ATP charge and thus allow a greater role for normal respiratory activity (Kriedemann and Downton 1981). However, without simultaneous measurement of 14C02-12C0, exchange the exact magnitude of rates of dark respiration, as effected by conditions of high insolation exposure, cannot be accurately determined at the present time (Coxson et al 1982).…”

Section: Discussionmentioning

confidence: 98%

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

Coxson¹

1987

Can. J. Bot.

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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...

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Physiological‐environmental Interactions in Lichens

Cited by 18 publications

References 16 publications

CO2 Exchange in soil algal crusts occurring in the trachypogon savannas of the Orinoco Llanos, Venezuela

CO2 Exchange in soil algal crusts occurring in the trachypogon savannas of the Orinoco Llanos, Venezuela

Photosynthesis in a sub‐Antarctic shore‐zone lichen

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

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