CO2 and O2 dynamics in leaves of aquatic plants with C3 or CAM photosynthesis - application of a novel CO2 microsensor (original) (raw)
Related papers
Internal CO2 Measured Directly in Leaves
Plant Physiology, 1992
Observations of nonuniform photosynthesis across leaves cast doubt on intemal CO2 partial pressures (p) calculated on the assumption of uniformity and can lead to incorrect conclusions about the stomatal control of photosynthesis. The problem can be avoided by measuring pi directly because the assumptions of uniformity are not necessary. We therefore developed a method that allowed pi to be measured confinuously in situ for days at a time under growth conditions and used it to investigate intact leaves of sunflower (Helianthus annuus L.), soybean (Glycine max L. Merr.), and bush bean (Phaseolus vulgaris L.) subjected to high or low leaf water potentials (I,) or high concentrations of abscisic acid (ABA). The leaves maintained a relatively constant differential (Ap) between ambient CO2 and measured pi throughout the light period when water was supplied. When water was withheld, ', decreased and the stomata began to close, but measured p increased until the leaf reached a *w of-1.76 (bush bean),-2.12 (sunflower) or-3.10 (soybean) megapascals, at which point Ap = 0. The increasing pi indicated that stomata did not inhibit CO2 uptake and a Ap of zero indicated that CO2 uptake became zero despite the high availability of CO2 inside the leaf. In contrast, when sunflower leaves at high Iw were treated with ABA, pi did not increase and instead decreased rapidly and steadily for up to 8 hours even as I, increased, as expected if ABA treatment primarily affected stomatal conductance. The accumulating CO2 at low Iw and contrasting response to ABA indicates that photosynthetic biochemistry limited photosynthesis at low Iw but not at high ABA. Water deficits have a large impact on plant growth and productivity by reducing leaf turgor, cell expansion, stomatal conductance, and photosynthesis and increasing ABA and solute concentrations in the tissues (2, 4). Among these responses, the inhibition of photosynthesis is central and often thought to be caused by reduced stomatal conductance, perhaps because of high ABA, that limits the availability of CO2 inside the leaf (8-10, 29, 32, 33). However, the ' Supported by grants from the DuPont Company and Department of Energy (DE-FG02-87ER1 3776).
Plant and Cell Physiology, 2006
The stoichiometric ratio of O 2 evolution to CO 2 uptake during photosynthesis reveals information about reductive metabolism, including the reduction of alternative electron acceptors, such as nitrite and oxaloacetate. Recently we reported that in simultaneous measurements of CO 2 uptake and O 2 evolution in a sunflower leaf, O 2 evolution changed by 7% more than CO 2 uptake when light intensity was varied. Since the O 2 /CO 2 exchange ratio is $1, small differences are important. Thus, these gas exchange measurements need precise calibration. In this work, we describe a new calibration procedure for such simultaneous measurements, based on the changes of O 2 concentration caused by the addition of pure CO 2 or O 2 into a flow of dry air (20.95% O 2 ) through one and the same capillary. The relative decrease in O 2 concentration during the addition of CO 2 and the relative increase in O 2 concentration during the addition of O 2 allowed us to calibrate the CO 2 and O 2 scales of the measurement system with an error (relative standard deviation, RSD) of 51%. Measurements on a sunflower leaf resulted in an O 2 /CO 2 ratio between 1.0 and 1.03 under different CO 2 concentrations and light intensities, in the presence of an ambient O 2 concentration of 20-50 mmol mol À1 . This shows that the percentage use of reductive power from photochemistry in synthesis of inorganic or organic matter other than CO 2 assimilation in the C 3 cycle is very low in mature leaves and, correspondingly, the reduction of alternative acceptors is a weak source of coupled ATP synthesis.
PLANT PHYSIOLOGY, 2004
We measured the oxygen isotope composition (d 18 O) of CO 2 respired by Ricinus communis leaves in the dark. Experiments were conducted at low CO 2 partial pressure and at normal atmospheric CO 2 partial pressure. Across both experiments, the d 18 O of dark-respired CO 2 (d R ) ranged from 44& to 324& (Vienna Standard Mean Ocean Water scale). This seemingly implausible range of values reflects the large flux of CO 2 that diffuses into leaves, equilibrates with leaf water via the catalytic activity of carbonic anhydrase, then diffuses out of the leaf, leaving the net CO 2 efflux rate unaltered. The impact of this process on d R is modulated by the d 18 O difference between CO 2 inside the leaf and in the air, and by variation in the CO 2 partial pressure inside the leaf relative to that in the air. We developed theoretical equations to calculate d 18 O of CO 2 in leaf chloroplasts (d c ), the assumed location of carbonic anhydrase activity, during dark respiration. Their application led to sensible estimates of d c , suggesting that the theory adequately accounted for the labeling of CO 2 by leaf water in excess of that expected from the net CO 2 efflux. The d c values were strongly correlated with d 18 O of water at the evaporative sites within leaves. We estimated that approximately 80% of CO 2 in chloroplasts had completely exchanged oxygen atoms with chloroplast water during dark respiration, whereas approximately 100% had exchanged during photosynthesis. Incorporation of the d 18 O of leaf dark respiration into ecosystem and global scale models of C 18 OO dynamics could affect model outputs and their interpretation.
Seibutsu kankyō chōsetsu, 2002
The CO2 dependent 02 evolution during the light period, at which the exogenous CO2 uptake was suspended, in 12 CAM plants (including pineapple (Ananas comosus)) was evaluated with a gas-phase oxygen electrode. At 5% CO2, the rate of photosynthetic 02 evolution in pineapple was saturated at 1 500 µmol m-2 s-1 PPFD and the maximum rate was 60 µmol m-2 s-1, which was 10 times those obtained at ambient CO2 conditions with the CO2 exchange system and significantly higher than the other CAM plants. At the saturated PPFD, the 02 evolution in pineapple substantially increased with increasing CO2 concentration up to 3% and decreased above 4%. However in the other CAM plants, such increment was small. By the use of a novel compensating CO2 gas exchange system, the rate of CO2 exchange in pineapple at very high CO2 was measured and found the enhancement of CO2 uptake in both light (Phases III and IV) and dark (Phase I) periods. Based on the results obtained, possibilities of the further increases in CO2 uptake in CAM plants, especially of pineapple, are discussed in terms of stomatal functions and malate storage capacities.
Responses of Ottelia alismoides, an aquatic plant with three CCMs, to variable CO2 and light
Journal of experimental botany, 2017
Ottelia alismoides is a constitutive C4 plant and bicarbonate user, and has facultative crassulacean acid metabolism (CAM) at low CO2. Acclimation to a factorial combination of light and CO2 showed that the ratio of phosphoenolpyruvate carboxylase (PEPC) to ribulose-bisphosphate carboxylase/oxygenase (Rubisco) (>5) is in the range of that of C4 plants. This and short-term response experiments showed that the activity of PEPC and pyruvate phosphate dikinase (PPDK) was high even at the end of the night, consistent with night-time acid accumulation and daytime carbon fixation. The diel acidity change was maximal at high light and low CO2 at 17-25 µequiv g-1 FW. Decarboxylation proceeded at ~2-3 µequiv g-1 FW h-1, starting at the beginning of the photoperiod, but did not occur at high CO2; the rate was greater at high, compared with low light. There was an inverse relationship between starch formation and acidity loss. Acidity changes account for up to 21% of starch production and st...
Vegetatio, 1993
Understanding how photosynthetic capacity acclimatises when plants are grown in an atmosphere of rising CO2 concentrations will be vital to the development of mechanistic models of the response of plant productivity to global environmental change. A limitation to the study of acclimatisation is the small amount of material that may be destructively harvested from long-term studies of the effects of elevation of CO2 concentration. Technological developments in the measurement of gas exchange, fluorescence and absorption spectroscopy, coupled with theoretical developments in the interpretation of measured values now allow detailed analyses of limitations to photosynthesis in vivo. The use of leaf chambers with Ulbricht integrating spheres allows separation of change in the maximum efficiency of energy transduction in the assimilation of CO2 from changes in tissue absorptance. Analysis of the response of CO2 assimilation to intercellular CO2 concentration allows quantitative determination of the limitation imposed by stomata, carboxylation efficiency, and the rate of regeneration of ribulose 1:5 bisphosphate. Chlorophyll fluorescence provides a rapid method for detecting photoinhibition in heterogeneously illuminated leaves within canopies in the field. Modulated fluorescence and absorption spectroscopy allow parallel measurements of the efficiency of light utilisation in electron transport through photosystems I and II in situ.
Planta, 2005
Dynamic patchiness of photosystem II (PSII) activity in leaves of the crassulacean acid metabolism (CAM) plant Kalanchoe¨daigremontiana Hamet et Perrier, which was independent of stomatal control and was observed during both the day/night cycle and circadian endogenous oscillations of CAM, was previously explained by lateral CO 2 diffusion and CO 2 signalling in the leaves [Rascher et al. (2001) Proc Natl Acad Sci USA 98:11801-11805; Rascher and Lu¨ttge (2002) Plant Biol 4:671-681].
Journal of Experimental Botany, 2003
The detection of 12 CO 2 emission from leaves in air containing 13 CO 2 allows simple and fast determination of the CO 2 emitted by different sources, which are separated on the basis of their labelling velocity. This technique was exploited to investigate the controversial effect of CO 2 concentration on mitochondrial respiration. The 12 CO 2 emission was measured in illuminated and darkened leaves of one C 4 plant and three C 3 plants maintained at low (30±50 ppm), atmospheric (350±400 ppm) and elevated (700±800 ppm) CO 2 concentration. In C 3 leaves, the 12 CO 2 emission in the light (R d) was low at ambient CO 2 and was further quenched in elevated CO 2 , when it was often only 20±30% of the 12 CO 2 emission in the dark, interpreted as the mitochondrial respiration in the dark (R n). R n was also reduced in elevated CO 2. At low CO 2 , R d was often 70±80% of R n , and a burst of 12 CO 2 was observed on darkening leaves of Mentha sativa and Phragmites australis after exposure for 4 min to 13 CO 2 in the light. The burst was partially removed at low oxygen and was never observed in C 4 leaves, suggesting that it may be caused by incomplete labelling of the photorespiratory pool at low CO 2. This pool may be low in sclerophyllous leaves, as in Quercus ilex where no burst was observed. R d was inversely associated with photosynthesis, suggesting that the R d /R n ratio re¯ects the re®xation of respiratory CO 2 by photosynthesizing leaves rather than the inhibition of mitochondrial respiration in the light, and that CO 2 produced by mitochondrial respiration in the light is mostly emitted at low CO 2 , and mostly re®xed at elevated CO 2. . In the leaves of the C 4 species Zea mays, the 12 CO 2 emission in the light also remained low at low CO 2 , suggesting ef®cient CO 2 re®xation associated with sustained photosynthesis in non-photorespiratory conditions. However, R n was inhibited in CO 2-free air, and the velocity of 12 CO 2 emission after darkening was inversely associated with the CO 2 concentration. The emission may be modulated by the presence of post-illumination CO 2 uptake deriving from temporary imbalance between C 3 and C 4 metabolism. These experiments suggest that this uptake lasts longer at low CO 2 and that the imbalance is persistent once it has been generated by exposure to low CO 2 .
PLANT PHYSIOLOGY, 1985
An experimental system consisting of a gas exchange column linked to an assimilation chamber has been developed to record continuously the free dissolved CO2 concentration in seawater containing marine plants. From experiments performed on the red macroalga Chondrus crisp,,s (Rhodophyta, Gigartinales), this measurement is in agreement with the free CO2 concentration calculated from the resistance to CO2 exchanges in a biphasic system (gas and liquid) as earlier reported. The response time of this apparatus is short enough to detect, in conditions of constant pH, a photosynthesis-caused gradient between free CO2 and HC03pools which half-equilibrates in 25 seconds. Abolished by carbonic anhydrase, the magnitude of this grdient increases with decreasing