scholarly journals Factors influencing the measurement of assimilation and stomatal conductance with the LI-COR 6400XT gas exchange system.

2018 ◽  
Author(s):  
Daniel LeCain ◽  
Sean Gleason
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Experimental Error ◽  
Leaf Age ◽  
Time Of Day ◽  
Species Variation ◽  
Plant Responses ◽  
Exchange System ◽  
Leaf Chamber ◽  
Gas Exchange System

Abstract: Although CO2 and H2O exchange rates are often measured in experiments as indicators of physiological plant responses these gas exchange measurements are prone to large experimental error. Gas exchange equipment and technology have improved greatly over the past two decades which supports scrutinizing current issues of experimental error in measuring plant photosynthesis and stomatal conductance. This report shows results of a greenhouse experiment with the goal of identifying lessor understood sources of experimental error and variation in measurements with the LI-COR 6400XT gas exchange system. A variety of plant types were used to encompass differing species variation. We found significant sources of experimental error in 1) the time for initial adjustment when placing a leaf in the leaf chamber 2) the time-of-day when measuring 3) leaf age 4) having the chamber window full vs. partially full with leaf tissue 5) using a leaf chamber environment that greatly diverges from the whole plant environment 6) differing degree of experimental error depending upon plant species. A situation with multiple contributors to error would result in useless gas-exchange data. Recommendations for minimizing these experimental errors are given.

scholarly journals Normal Cyclic Variation in CO2 Concentration in Indoor Chambers Decreases Leaf Gas Exchange and Plant Growth

Plants ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 663
Author(s):  
James Bunce
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Leaf Gas Exchange ◽  
Genetic Material ◽  
Co2 Concentration ◽  
Cyclic Variation ◽  
Indoor Exposure ◽  
Elevated Atmospheric Co2 ◽  
Gas Exchange System ◽  
Opening And Closing

Attempts to identify crop genetic material with larger growth stimulation at projected elevated atmospheric CO2 concentrations are becoming more common. The probability of reductions in photosynthesis and yield caused by short-term variation in CO2 concentration within elevated CO2 treatments in the free-air CO2 enrichment plots raises the question of whether similar effects occur in glasshouse or indoor chamber experiments. These experiments were designed to test whether even the normal, modest, cyclic variation in CO2 concentration typical of indoor exposure systems have persistent impacts on photosynthesis and growth, and to explore mechanisms underlying the responses observed. Wheat, cotton, soybeans, and rice were grown from seed in indoor chambers at a mean CO2 concentration of 560 μmol mol−1, with “triangular” cyclic variation with standard deviations of either 4.5 or 18.0 μmol mol−1 measured with 0.1 s sampling periods with an open path analyzer. Photosynthesis, stomatal conductance, and above ground biomass at 20 to 23 days were reduced in all four species by the larger variation in CO2 concentration. Tests of rates of stomatal opening and closing with step changes in light and CO2, and tests of responses to square-wave cycling of CO2 were also conducted on individual leaves of these and three other species, using a leaf gas exchange system. Reduced stomatal conductance due to larger amplitude cycling of CO2 during growth occurred even in soybeans and rice, which had equal rates of opening and closing in response to step changes in CO2. The gas exchange results further indicated that reduced mean stomatal conductance was not the only cause of reduced photosynthesis in variable CO2 conditions.

scholarly journals Chronicvs.Short-Term Acute O3Exposure Effects on Nocturnal Transpiration in Two Californian Oaks

2007 ◽  
Vol 7 ◽  
pp. 134-140 ◽  
Author(s):  
N. E. Grulke ◽  
E. Paoletti ◽  
R. L. Heath
Keyword(s):  
Gas Exchange ◽  
Water Loss ◽  
Exchange System ◽  
Short Term ◽  
Blue Oak ◽  
Unexposed Control ◽  
Nocturnal Transpiration ◽  
Gas Exchange System ◽  
Black Oak ◽  
Oak Seedlings

We tested the effect of daytime chronic moderate ozone (O3) exposure, short-term acute exposure, and both chronic and acute O3exposure combined on nocturnal transpiration in California black oak and blue oak seedlings. Chronic O3exposure (70 ppb for 8 h/day) was implemented in open-top chambers for either 1 month (California black oak) or 2 months (blue oak). Acute O3exposure (~1 h in duration during the day, 120–220 ppb) was implemented in a novel gas exchange system that supplied and maintained known O3concentrations to a leaf cuvette. When exposed to chronic daytime O3exposure, both oaks exhibited increased nocturnal transpiration (without concurrent O3exposure) relative to unexposed control leaves (1.8× and 1.6×, black and blue oak, respectively). Short-term acute and chronic O3exposure did not further increase nocturnal transpiration in either species. In blue oak previously unexposed to O3, short-term acute O3exposure significantly enhanced nocturnal transpiration (2.0×) relative to leaves unexposed to O3. California black oak was unresponsive to (only) short-term acute O3exposure. Daytime chronic and/or acute O3exposures can increase foliar water loss at night in deciduous oak seedlings.

scholarly journals Gas exchanges and photosynthetic efficiency in sub-forest species from Atlantic Forest

2020 ◽  
Vol 9 (5) ◽  
pp. e43952870
Author(s):  
Magnólia Martins Alves ◽  
Manoel Bandeira de Albuquerque ◽  
Renata Ranielly Pedroza Cruz ◽  
Mário Luiz Farias Cavalcanti
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Water Use ◽  
Co2 Concentration ◽  
Time Of Day ◽  
Forest Understory ◽  
Forest Species ◽  
Gas Exchanges ◽  
Endogenous Factors ◽  
Intrinsic Efficiency

The availability of light is one of the factors that most limits the photosynthesis of juvenile trees in the understory of the forest. The study was carried out in the Mata do Pau-Ferro State Park, located in the city of Areia, PB. The objective of this study was to evaluate how gas exchanges occur in individuals of Psychotria colorata (Willd. Ex Roem & Schult.), Senna georgica Irwin & Barneby, Himatanthus phagedaenicus (Mart.) Woodson, Solanum swartzianum Roem. & Schult, Psychotria carthagenensis Jacq.e Psychotria hoffmannseggiana (Willd. ex Schult.) in the understory of a remnant of Mata Atlântica. The rate of photosynthesis (A), transpiration (E), stomatal conductance (Gs), internal CO2 concentration (Ci) leaf temperature-air temperature (°C), and internal carbon (Ci), instantaneous efficiency of water use (EUA) (A/E), Intrinsic efficiency of water use (EiUC) (A/Gs) and the intrinsic efficiency of carboxylation (ratio A/Ci). The rates of maximum photosynthesis (A), photosynthesis (E) and stomatal conductance (Gs) were shown to be influenced by the time of day, as there was no interference of external factors in the diurnal patterns of gas exchange, variations are due to endogenous factors, probably due to the circadian rhythm. The parameter of the gas exchange of sub-forest species responds differently, in the small variations in the luminosity levels of the forest understory

Regulation of Carboxylation and Photosynthetic Oscillations During Sun-Shade Acclimation in Helianthus annuus Measured With a Rapid-Response Gas Exchange System

1988 ◽  
Vol 15 (2) ◽  
pp. 239 ◽  
Author(s):  
CB Osmond ◽  
V Oja ◽  
A Laisk
Keyword(s):  
Gas Exchange ◽  
Intercellular Co2 Concentration ◽  
Photosynthetic Apparatus ◽  
Co2 Concentration ◽  
Rapid Response ◽  
Exchange System ◽  
Dynamic Regulation ◽  
Bisphosphate Carboxylase ◽  
Shade Acclimation ◽  
Gas Exchange System

The consequences of acclimation from shade to sun and vice versa for regulated photosynthetic metabolism were examined in H. annuus. A rapid-response gas exchange system was used to assess changes in carboxylation-related parameters (mesophyll conductance, assimilatory charge and CO2 capacity) and to analyse oscillations in CO2 fixation following transfer to high CO2 concentration as a function of intercellular CO2 concentration and light intensity. Data showed a two- to threefold change in all carboxylation-related parameters during acclimation in either direction. Dynamic regulation of carboxylation, indicated by changes in oscillatory response as a function of CO2 concentration at light saturation, remained unchanged, consistent with concerted regulation of ribulose-1,5-bisphosphate carboxylase-oxygenase during acclimation. However, the light dependency of oscillations changed during acclimation from shade to sun, and the range of oscillation was closely tied to the maximum rate of steady-state photosynthesis at CO2 saturation. These data imply that changes in the light-absorbing and electron transport components of the photosynthetic apparatus underlie the shift in regulatory behaviour during acclimation.

Gas-blood PCO2 gradients during avian gas exchange

1975 ◽  
Vol 39 (3) ◽  
pp. 405-410 ◽  
Author(s):  
D. G. Davies ◽  
R. E. Dutton
Keyword(s):  
Gas Exchange ◽  
Exchange System ◽  
Arterial Pco2 ◽  
Charged Membrane ◽  
Venous Pco2 ◽  
Avian Lung ◽  
Gas Exchange System ◽  
Spontaneously Breathing ◽  
Membrane Mechanism ◽  
Mixed Venous

The avian respiratory system is a crosscurrent gas exchange system. One of the aspects of this type of gas exchange system is that end-expired PCO2 is greater than arterial PCO2, the highest possible value being equal to mixed venous PCO2. We made steady-state measurements of arterial, mixed venous, and end-expired PCO2 in anesthetized, spontaneously breathing chickens during inhalation of room air or 4–8% CO2. We found end-expired PCO2 to be higher than both arterial and mixed venous PCO2, the sign of the differences being such as to oppose passive diffusion. The observation that end-expired PCO2 was higher than arterial PCO2 can be explained on the basis of crosscurrent gas exchange. However, the observation that end-expired PCO2 exceeded mixed venous PCO2 must be accounted for by some other mechanism. The positive end-expired to mixed venous PCO2 gradients can be explained if it is postulated that the charged membrane mechanism suggested by Gurtner et al. (Respiration Physiol. 7: 173–187, 1969) is present in the avian lung.

scholarly journals Food production and gas exchange system using blue-green alga (Spirulina) for CELSS

1987 ◽  
Vol 7 (4) ◽  
pp. 7-10 ◽  
Author(s):  
Mitsuo Oguchi ◽  
Koji Otsubo ◽  
Keiji Nitta ◽  
Shigeki Hatayama
Keyword(s):  
Gas Exchange ◽  
Green Alga ◽  
Food Production ◽  
Blue Green Alga ◽  
Exchange System ◽  
Gas Exchange System
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