Diurnal and Seasonal Patterns of Photosynthesis and Respiration by Stems of Populus tremuloides Michx.

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The physiological responses of 6-to 8-year-old aspen (Populus tremuloides Michx.) stems to temperature, light, and CO2 concentration were investigated in the field throughout the year using infrared CO2 analysis. Light response studies showed that the rate of gross photosynthesis was linear from 0 to 400 ft-c (0 to 1.6 mw/cm2 of 400-700 nm) with light saturation being reached between 800 to 1400 ft-c (3.2 to 5.6 mw/cm2 of 400-700 nm). At this light intensity, the respiratory CO2 loss was reduced to 10 to 15% of dark rates. Net photosynthetic CO2 uptake was not observed even at intensities as high as 3400 ft-c (13.6 mw/cm2 of 400-700 nm). The light response curve was similar for both winter and summer stems.During summer months, the respiratory and photosynthetic rates of the aspen stem increased with temperature at a near constant rate between 5 and 35 C. For winter stems, the gross photosynthetic rate increased in a pattern similar to the dark respiratory rate as the temperature rose from 3 to 17 C. Below 0 C and above 17 C, however, the gross photosynthetic rate feD off in relation to the respiratory rate so that the per cent of CO2 reassimilated decreased from 75% to less than 50%. Measurable bark photosynthetic activity was not observed below -3 C.The gross photosynthetic rate of stems was not affected when the gas passing through the cuvette contained concentrations of CO2 ranging from 0 to 580 ,ul CO2/l air.Twigs and stems of living shrubs and trees have a greenish corticular layer just beneath the bark surface. The green pigment is Chl which is concentrated in photosynthetically active chloroplasts (17). Photosynthesis by the stem is termed corticular photosynthesis (20) or bark photosynthesis.Most species in which bark photosynthesis has been investigated were not capable of net photosynthesis, but stem photosynthesis did reduce substantially the respiratory loss of CO., from the stem (1, 8-10, 13, 16, 19 No fertilizer was added in 1973. The trees were watered every 1 to 3 days so that the soil moisture tension in each box was maintained between 0 and 100 centibars. Extensive use of the trees was started 1 year after the transplanting to allow for site adjustment. The boxed trees were healthy and vigorous as evident from the rates of shoot growth, the color and size of the leaves, and the width of the growth rings. Bud break occurred April 18 to 25, 1973; leaf fall, October 12 to 26, 1973. Bark slippage commenced in mid-April and ceased in October. Stem diameters were observed to increase from mid-May through mid-August.Photosynthetic and respiratory CO, exchange rates were measured using a 30-cm, water-cooled, acrylic plastic cuvette consisting of two halves that could be placed around the stem and sealed with no apparent injury to the stem (5). To reduce water, CO2, and heat gradients within the cuvette, an air recirculation system was used with the cooling coils submerged in water or a water-ethanol mixture depending on the operating temperature (5).An open system was used from June to Augus...

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Physiological Characteristics of Photosynthesis and Respiration in Stems of Populus tremuloides Michx.

Foote

Schaedle²

1976

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Section: Introductionmentioning

confidence: 99%

“…Photosynthesis in woody stems is best known in the bark of quaking aspen, Populus tremuloides 17,19,20, 22). Net CO2 assimilation by illuminated aspen bark has never been reported, but photosynthesis (reduction of CO2 release rates on illuminated) is known to occur over a wide range of temperatures and during all seasons of the year (9,10,17).Although the photosynthetic performance of older stem tissues is reasonably well studied, little is known about growing internodes of woody species. Because young, growing stems of woody species intergrade from an entirely primary tissue system to a predominately secondary tissue system, the photosynthetic and respiratory rates of juvenile aspen stem could vary with the age and developmental stage of the internodes.…”

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confidence: 99%

Photosynthesis and Respiration of Developing Populus tremuloides Internodes

Brayman

Schaedle²

1982

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The photosynthetic and respiratory performance of developing internodes of Popudus tremuloides was evaluated by infrared gas analysis.Anatomical and morphological transitions were related to metabolic activity. Photosynthetic rates ranged from 6.0 to 10.0 milligrams CO2 per decimeter squared per hour in the youngest internodes to 2.5 to 3.8 milligrams CO2 per decimeter squared per hour in internodes with fully developed bark tissues. Respiration exceeded the rate of photosynthesis on the average by a factor of two. Stem photosynthesis increased with temperature up to 40°C and declined steeply between 40 and 50°C. Stem respiration increased nearly linearly to temperatures as high as 50°C.In the last twenty years, considerable effort has been devoted to the study of bark photosynthesis (5,10,16,21). Photosynthesis in woody stems is best known in the bark of quaking aspen, Populus tremuloides 17,19,20, 22). Net CO2 assimilation by illuminated aspen bark has never been reported, but photosynthesis (reduction of CO2 release rates on illuminated) is known to occur over a wide range of temperatures and during all seasons of the year (9,10,17).Although the photosynthetic performance of older stem tissues is reasonably well studied, little is known about growing internodes of woody species. Because young, growing stems of woody species intergrade from an entirely primary tissue system to a predominately secondary tissue system, the photosynthetic and respiratory rates of juvenile aspen stem could vary with the age and developmental stage of the internodes. This study was undertaken to investigate developmental changes in aspen internode metabolic rates as related to the plastochron age (7,15)

“…The IR gas analyzer is the instrument most commonly used to measure CO2 concentrations. Flow-through systems which monitor CO2 exchange of plants or plant parts enclosed in a chamber usually depend on the detection of a 10 to 30 pl C02/1 concentration differential between input and exhaust air (3,(7)(8)(9)12). The CO2 differentials can be related to net photosynthesis or respiration.…”

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confidence: 99%

A Sensitive Technique for the Rapid Measurement of Carbon Dioxide Concentrations

Clegg¹,

Sullivan²,

Eastin³

1978

102

A method has been developed to measure concentratons of CO2 in gases rapidy. A gas sample is injected into a flowing carrier gas that passes through an Inrared CO2 analyzer. A strip chart recorded peak respome is obtained which is proportional to the CO2 concentration. A resolution of better than 2 microliters of CO2 per liter of gas was obtained.Seven to 10 seconds were required for sample analysis once the sample was obtained. So bum iclor plant respirto was deterned at different temperatures by measuring CO2 using this system ad by using a conventonl system. The correlaton between tehqs was 0.996, and about the same variation occurred within each method. This te ue greatly increased the efficiency of the infrared CO2 analyr in our laboratory for use in plant resprato d photosynthetic studies.The concentration of CO2 in gases is frequently measured in environmental and biological studies. Both respiration and photosynthesis can be monitored by measuring CO2 exchange. Because analysis of a large number of samples is often necessary, the method for measurement should be rapid and sensitive. The IR gas analyzer is the instrument most commonly used to measure CO2 concentrations. Flow-through systems which monitor CO2 exchange of plants or plant parts enclosed in a chamber usually depend on the detection of a 10 to 30 pl C02/1 concentration differential between input and exhaust air (3,(7)(8)(9)12). The CO2 differentials can be related to net photosynthesis or respiration. CO2 concentrations of the air surrounding photosynthesizing plants can also be monitored and a concentration level maintained by automatically injecting CO2. The amount of CO2 added is equal to net photosynthesis (5,11). In the field, photosynthesis may be determined aerodynamically by determining the CO2 gradients within the crop canopy (4, 6, 10).In many photosynthetic studies determination of CO2 concentrations requires an IR gas analyzer to monitor continuously a single CO2 exchange chamber, or several chambers may be monitored consecutively with a sample switching device at the analyzer while continually purging the sampling lines. After switching, I to several min equilibration time is usually necessary to stabilize the analyzer and obtain a reliable reading (13).A method for measuring CO2 in small volumes of gas has been described which was used in a working range generally between 1,000 and 15,000 1s1/1 CO2 (1 MATERIALS AND METHODSThe basic system consisted of an IR gas analyzer, mv recorder, flow meter, and drying columns (Fig. 1). Tygon2 tubing was used to connect the system. The tubing lengths from the tee connector to the IR gas analyzer were the same to balance line resistance. The flow rate of the carrier gas (usually N2) was adjusted to approximately 0.6 I/min. At this flow, a narrow based peak was recorded on the strip chart recorder and only measurement of peak heights was necessary to obtain the CO2 concentration ofthe injected gas sample. A 10-ml or less sample was injected with a syringe through a short section of sur...