Passive CO2 concentration in higher plants (original) (raw)
Related papers
CO2 sequestration in plants: lesson from divergent strategies
Photosynthetica, 2011
Most organisms inhabiting earth feed directly or indirectly on the products synthesized by the reaction of photosynthesis, which at the current atmospheric CO 2 levels operates only at two thirds of its peak efficiency. Restricting the photorespiratory loss of carbon and thereby improving the efficiency of photosynthesis is seen by many as a good option to enhance productivity of food crops. Research during last half a century has shown that several plant species developed CO 2-concentrating mechanism (CCM) to restrict photorespiration under lower concentration of available CO 2. CCMs are now known to be operative in several terrestrial and aquatic plants, ranging from most advanced higher plants to algae, cyanobacteria and diatoms. Plants with C 4 pathway of photosynthesis (where four-carbon compound is the first product of photosynthesis) or crassulacean acid metabolism (CAM) may consistently operate CCM. Some plants however can undergo a shift in photosynthetic metabolism only with change in environmental variables. More recently, a shift in plant photosynthetic metabolism is reported at high altitude where improved efficiency of CO 2 uptake is related to the recapture of photorespiratory loss of carbon. Of the divergent CO 2 assimilation strategies operative in different oraganisms, the capacity to recapture photorespiratory CO 2 could be an important approach to develop plants with efficient photosynthetic capacity.
Lateral Diffusion of CO2 in Leaves Is Not Sufficient to Support Photosynthesis
PLANT PHYSIOLOGY, 2005
Lateral diffusion of CO 2 was investigated in photosynthesizing leaves with different anatomy by gas exchange and chlorophyll a fluorescence imaging using grease to block stomata. When one-half of the leaf surface of the heterobaric species Helianthus annuus was covered by 4-mm-diameter patches of grease, the response of net CO 2 assimilation rate (A) to intercellular CO 2 concentration (C i ) indicated that higher ambient CO 2 concentrations (C a ) caused only limited lateral diffusion into the greased areas. When single 4-mm patches were applied to leaves of heterobaric Phaseolus vulgaris and homobaric Commelina communis, chlorophyll a fluorescence images showed dramatic declines in the quantum efficiency of photosystem II electron transport (measured as F q #/F m #) across the patch, demonstrating that lateral CO 2 diffusion could not support A. The F q #/F m # values were used to compute images of C i across patches, and their dependence on C a was assessed. At high C a , the patch effect was less in C. communis than P. vulgaris. A finite-volume porous-medium model for assimilation rate and lateral CO 2 diffusion was developed to analyze the patch images. The model estimated that the effective lateral CO 2 diffusion coefficients inside C. communis and P. vulgaris leaves were 22% and 12% of that for free air, respectively. We conclude that, in the light, lateral CO 2 diffusion cannot support appreciable photosynthesis over distances of more than approximately 0.3 mm in normal leaves, irrespective of the presence or absence of bundle sheath extensions, because of the CO 2 assimilation by cells along the diffusion pathway. * Corresponding author; e-mail morisj@essex.ac.uk; fax 44-1206-872592.
Planta, 1972
The development of peripheral reticulum (PR) in chloroplasts varies in C 3 and C 4 plants. In general, PR is more extensive in Ct plants, but PR is also seen in the chloroplasts of some C a plants. Within some C 4 plants, PR is seen in the bundle sheath cells which predominantly use the C a pathway. Thus, PR is not associated directly with the presence of the C~ pathway on a cellular basis. Its predominance in C 4 plants must be related to some characteristic other than the method of CO 2 fixation. Ultrastructural evidence suggests that PR is associated with the rapid transfer of substances into and out of chloroplasts and from mesophyll to bundle sheath cells.
Physiological and Biochemical Strategies for CO2 Fixation in Plants
Agricultura, 2019
The photosynthetic carbon assimilation pathways are not the same for all plants; they show great inventiveness through their adaptations to low CO2 concentrations, high O2, water stress, but also to different temperatures in the environments in which they live. From this point of view there are 3 photosynthetic cycles in plants: C3, C4 and CAM.
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].
PLANT PHYSIOLOGY, 1989
Photosynthesis rates of detached Panicum miliaceum leaves were measured, by either CO2 assimilation or oxygen evolution, over a wide range of CO2 concentrations before and after supplying the phosphoenolpyruvate (PEP) carboxylase inhibitor, 3,3dichloro-2-(dihydroxyphosphinoyl-methyl)-propenoate (DCDP). At a concentration of CO2 near ambient, net photosynthesis was completely inhibited by DCDP, but could be largely restored by elevating the CO2 concentration to about 0.8% (v/v) and above. Inhibition of isolated PEP carboxylase by DCDP was not competitive with respect to HC03-, indicating that the recovery was not due to reversal of enzyme inhibition. The kinetics of 14C-incorporation from 14CO2 into early labeled products indicated that photosynthesis in DCDP-treated P. miliaceum leaves at 1% (v/v) CO2 occurs predominantly by direct CO2 fixation by ribulose 1,5bisphosphate carboxylase. From the photosynthesis rates of DCDP-treated leaves at elevated CO2 concentrations, permeability coefficients for CO2 flux into bundle sheath cells were determined for a range of C4 species. These values (6-21 micromoles per minute per milligram chlorophyll per millimolar, or 0.0016-0.0056 centimeter per second) were found to be about 100-fold lower than published values for mesophyll cells of C3 plants. These results support the concept that a CO2 permeability barrier exists to allow the development of high CO2 concentrations in bundle sheath cells during C4 photosynthesis.
Integration of photosynthetic acclimation to CO2 at the whole-plant level
Global Change Biology - GLOB CHANGE BIOL, 1998
Primary events in photosynthetic (PS) acclimation to elevated CO2 concentration ([CO2]) occur at the molecular level in leaf mesophyll cells, but final growth response to [CO2] involves acclimation responses associated with photosynthate partitioning among plant organs in relation to resources limiting growth. Source–sink interactions, particularly with regard to carbon (C) and nitrogen (N), are key determinants of PS acclimation to elevated [CO2] at the whole-plant level. In the long term, PS and growth response to [CO2] are dependent on genotypic and environmental factors affecting the plant's ability to develop new sinks for C, and acquire adequate N and other resources to support an enhanced growth potential. Growth at elevated [CO2] usually increases N use efficiency because PS rates can be maintained at levels comparable to those observed at ambient [CO2] with less N investment in PS enzymes. A frequent acclimation response, particularly under N-limited conditions, is for the accumulation of leaf carbohydrates at elevated [CO2] to lead to repression of genes associated with the production of PS enzymes. The hypothesis that this is an adaptive response, leading to a diversion of N to plant organs where it is of greatest benefit in terms of competitive ability and reproductive fitness, needs to be more rigorously tested.The biological control mechanisms which plants have evolved to acclimate to shifts in source–sink balance caused by elevated [CO2] are complex, and will only be fully elucidated by probing at all scales along the hierarchy from molecular to ecosystem. Use of environmental manipulations and genotypic comparisons will facilitate the testing of specific hypotheses. Improving our ability to predict PS acclimation to [CO2] will require the integration of results from laboratory studies using simple model systems with results from whole-plant studies that include measurements of processes operating at several scales.Abbreviations: CAM, crassulacean acid metabolism; FACE, Free-Air CO2 Enrichment; Pi, inorganic phosphate; LAR, leaf area ratio (m2 g-1); LWR, leaf weight ratio (g g-1); NAR, net assimilation rate (g m-2 d- 1); PS, photosynthetic; RGR, relative growth rate (g g-1 d-1); R:S, root/shoot ratio; rubisco, ribulose bisphosphate carboxylase/oxygenase; RuBP, ribulose bisphosphate; SLA, specific leaf area (m2 g-1); SPS, sucrose phosphate synthase; WUE, water use efficiency (g biomass g H2O-1).
The photosynthesis game is in the "inter-play": Mechanisms underlying CO2 diffusion in leaves
Environmental and Experimental Botany, 2020
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Recent developments in mesophyll conductance in C3, C4, and crassulacean acid metabolism plants
The Plant Journal
The conductance of carbon dioxide (CO 2) from the substomatal cavities to the initial sites of CO 2 fixation (g m) can significantly reduce the availability of CO 2 for photosynthesis. There have been many recent reviews on: (i) the importance of g m for accurately modelling net rates of CO 2 assimilation, (ii) on how leaf biochemical and anatomical factors influence g m , (iii) the technical limitation of estimating g m , which cannot be directly measured, and (iv) how g m responds to long-and short-term changes in growth and measurement environmental conditions. Therefore, this review will highlight these previous publications but will attempt not to repeat what has already been published. We will instead initially focus on the recent developments on the two-resistance model of g m that describe the potential of photorespiratory and respiratory CO 2 released within the mitochondria to diffuse directly into both the chloroplast and the cytosol. Subsequently, we summarize recent developments in the three-dimensional (3-D) reaction-diffusion models and 3-D image analysis that are providing new insights into how the complex structure and organization of the leaf influences g m. Finally, because most of the reviews and literature on g m have traditionally focused on C 3 plants we review in the final sections some of the recent developments, current understanding and measurement techniques of g m in C 4 and crassulacean acid metabolism (CAM) plants. These plants have both specialized leaf anatomy and either a spatially or temporally separated CO 2 concentrating mechanisms (C 4 and CAM, respectively) that influence how we interpret and estimate g m compared with a C 3 plants.
Leaf Functional Anatomy in Relation to Photosynthesis
PLANT PHYSIOLOGY, 2011
Rubisco is a large enzyme with a molecular mass of approximately 550 kD. The maximum rate of CO 2 fixation (i.e. ribulose-1,5-bisphosphate [RuBP] carboxylation) at CO 2 saturation is only 15 to 30 mol CO 2 mol 21 Rubisco protein s 21 at 25°C. Affinity to CO 2 is also low, and the K m , K c , at 25°C in the absence of oxygen is comparable to the CO 2 concentration in water equilibrated with air containing 39 Pa CO 2 (approximately 390 mL L 21 ), 13 mM. Moreover, RuBP carboxylation is competitively inhibited by RuBP oxygenation, which is the primary step of the energy-wasting process, photorespiration. If the CO 2 concentration in the chloroplast stroma is low, the carboxylation rate will decrease while the oxygenation rate will increase. Under such conditions, light energy and other resources, including nitrogen and water, are all wasted, eventually leading to a decrement of fitness of the plants. From these data, we may consider that structural features of the leaf contributing to the maintenance of the high CO 2 concentration in the chloroplast stroma may have been selected during evolution.