Measurement of CO<sub>2</sub> exchange in lichens: a new method

Larson, Douglas W.; Kershaw, K. A.

doi:10.1139/b75-184

Cited by 95 publications

(56 citation statements)

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“…The discrete sampling method for measuring COg in lichens (Larson and Kershaw, 1975c) was used throughout. Busby and Whitfield (1978) have recently criticized these methods and conducted a comprehensive error analysis of them.…”

Section: Infrared Gas Analysismentioning

confidence: 99%

“…The water used was tap water which had stood for more than 48 h. The plants were soaked for a period of 1 h. This amount of time allowed for steady-state rates of gas exchange to be obtained in these species (Larson, 1979a). After this time, the response of net photosynthesis and respiration to thallus moisture content as the plants slowly dried out, was monitored using the methods described in Larson and Kershaw (1975c). The data were expressed as mg CO2 h^^ g dry wt-^ of tissue.…”

Section: Infrared Gas Analysismentioning

confidence: 99%

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SEASONAL CHANGE IN THE PATTERN OF NET CO₂ EXCHANGE IN UMBILICARIA LICHENS

Larson

1980

New Phytologist

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SUMMARYThe response of net photosynthesis and respiration in five species of Umbilicaria to thallus moisture content at three temperatures (0, 14, 28 °C) and four light intensities (0, 100, 330, 700 Hmo\ m~* s"^) was studied in collections made in summer and winter.The pattern of response to these variables suggests that each species is uniquely adapted to the cliff environments in which they grow. A simple model suggests further that each species can maintain a positive energy balance provided that its distribution does not extend to sites with temperatures in excess of certain values.None of the species show photosynthetic acclimation to temperature, yet they all exhibit large seasonal changes in their response structures. The significance of such patterns is discussed.

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Section: Infrared Gas Analysismentioning

confidence: 99%

Section: Infrared Gas Analysismentioning

confidence: 99%

SEASONAL CHANGE IN THE PATTERN OF NET CO₂ EXCHANGE IN UMBILICARIA LICHENS

Larson

1980

New Phytologist

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“…Larson and Kershaw (13) formed to percentage maximum NPR) with saturation at about 450 ,ul I` (Fig. 2).…”

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confidence: 95%

“…Several authors (1,4,13) have described independently a method of adapting IRGA2 for use as discrete sample analyzers whereby small volumes of gas samples (1-3 ml) can be injected, via a carrier gas, directly into the analysis tube of an IRGA. The 'This investigation was supported by equipment grants to TGAG and a University Grants Committee postgraduate studentship to WPS from the University Grants Committee.…”

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confidence: 99%

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Carbon Dioxide Exchange in Lichens

Green

Snelgar²

1981

Plant Physiol.

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The relationship between net photosynthesis and CO2 concentration was investigated for four species of lichen using an infrared gas analyzer operating in a closed loop system. All species showed a linear relationship at low CO2 levels (100 microliters per liter) with CO2 saturation levels being in excess of 400 microliters per liter. Detailed studies of Sticta latifrons showed a strong influence of thallus water content which resulted in the net photosynthetic response at high water contents still being nearly linear at 1000 microliters per liter CO2. Very low CO2 compensation values (5 microliters per liter) were obtained under some conditions but the value varied between thalli and with thallus water content. The results differ from previous studies which reported low CO2 saturation levels (200 microliters per liter) and no apparent effect of water content. It is suggested that some of these differences may result from the use of a discrete sampling injection infrared gas analyzer system in the earlier studies and an assessment is made of the influence of nonsaturating CO2 levels, lack of cuvette ventilation, and data presentation for this technique.Studies of photosynthesis in lichens have been made by a variety of techniques including the measurement of "C uptake (6-8), changes in gas volume both by manometry (17), a cartesian diver system (16), and 02 concentration with an 02 electrode (2).Most of these methods have the disadvantage that the lichens are subjected to highly unnatural conditions, such as immersion in buffer solutions and exposure to CO2 and 02 concentrations, which differ markedly from ambient levels. The results of '4C uptake experiments also present interpretation difficulties as the gross photosynthetic rate of lichens is substantially greater than the net photosynthetic rate. More recently, most studies of the rates of CO2 exchange have used an infrared gas analyzer system, sometimes with an adaptation of a flow-through cell (9) to allow simultaneous determination of CO2 exchange and water content.However, the low resistance to water loss common to all lichens (3), coupled with the close interdependence of gas exchange rates and thallus water content, led to the use of low flow rates and, in some instances, this resulted in substantial systematic errors (see Larson and Kershaw (13) for discussion).Several authors (1, 4, 13) have described independently a method of adapting IRGA2 for use as discrete sample analyzers whereby small volumes of gas samples (1-3 ml) can be injected, via a carrier gas, directly into the analysis tube of an IRGA. The 'This investigation was supported by equipment grants to TGAG and a University Grants Committee postgraduate studentship to WPS from the University Grants Committee. 2Abbreviation: IRGA, infrared gas analyzer; NPR, net photosynthetic rate. maximum deflection of the IRGA is found to be proportional to the quantity of CO2 injected, thus, for constant injection volume, it is proportional to the CO2 concentration of the injected gas.Recently, thi...

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