Crassulacean Acid Metabolism: A Curiosity in Context

Osmond, C. B.

doi:10.1146/annurev.pp.29.060178.002115

Cited by 873 publications

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“…Declining leaf water potential is a powerful driver of stomatal closure in C 3 plants (Rodriguez-Dominguez et al, 2016). Although comparative data are quite limited, succulent CAM plant stomata tend to close at much higher (less negative) water potentials than those of co-occurring C 3 plants (Osmond, 1978), consistent with evidence that succulent plants tend to avoid, or be isolated from, drought stress (Nobel, 1988;J. Males and H. Griffiths, unpublished data). Complete stomatal closure can therefore occur throughout both the light and dark periods (CAM idling).…”

Section: Stomatal Responses To External Stimulimentioning

confidence: 56%

“…1; Osmond, 1978). Stomatal conductance is typically highest during the dark period (Phase I), in association with nocturnal CO 2 assimilation by PEPC.…”

Section: Patterns Of Stomatal Conductancementioning

confidence: 99%

“…The involvement of organic anions in stomatal regulation has interesting implications for CAM plants, in which malate can accumulate to high concentrations during Phase I (Osmond, 1978). The importance of abscisic acid (ABA), which is synthesized and mobilized in roots and shoots in response to declining water potential, in regulating stomatal closure in CAM plants, compared to C 3 plants, remains to be determined (Cutler, 2017;Jezek and Blatt, 2017).…”

Section: Stomatal Responses To External Stimulimentioning

confidence: 99%

“…The physiological mechanisms and ecological significance of the gas exchange rhythms of plants performing CAM have been the subject of curiosity and investigation for not just decades, but centuries (De Saussure, 1804;Heyne, 1815;Osmond, 1978;Ting, 1987;Faak, 2000). The quintessential feature of CAM is nocturnal primary carbon assimilation by the enzyme phospho-enol-pyruvate carboxylase (PEPC), producing malic acid that is stored in mesophyll cell vacuoles and subsequently decarboxylated during the light period to provide CO 2 for refixation by Rubisco .…”

mentioning

confidence: 99%

“…Researchers have adopted a multiplicity of approaches to shed light on these questions, spurred both by the enduring appeal of CAM as a "curiosity" (Osmond, 1978) and the rapidly growing interest in the application and engineering of CAM plants for bioenergy production (Borland et al, 2011(Borland et al, , 2014(Borland et al, , 2015Owen and Griffiths, 2014;DePaoli et al, 2014;Yang et al, 2015). Simultaneously, the wider field of stomatal biology has experienced a renaissance in recent years, with numerous advances being made through both empirical and theoretical work.…”

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confidence: 99%

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Stomatal Biology of CAM Plants

Males

Griffiths

2017

Plant Physiol.

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ORCID ID: 0000-0001-9899-8101 (J.M.).Crassulacean acid metabolism (CAM) is a major physiological syndrome that has evolved independently in numerous land plant lineages. CAM plants are of great ecological significance, and there is increasing interest for their water-use efficiency and drought resistance. Integral to the improvement in water-use efficiency that CAM affords is a unique pattern of stomatal conductance, distinguished by primarily nocturnal opening and often extensive diurnal flexibility in response to environmental factors. Here, we assess how recent research has shed new light on the functional biology of CAM plant stomata and integration within the broader physiology and ecology of succulent organisms. Divergences in stomatal sensitivity to environmental and endogenous factors relative to C 3 species have been a key aspect of the evolution of functional CAM. Stomatal traits of CAM plants are closely coordinated with other leaf functional traits, and structural specialization of CAM stomatal complexes may be of undiagnosed functional relevance. We also highlight how salient results from ongoing work on C 3 plant stomatal biology could apply to CAM species. Key questions remaining relate to the interdependence between stomatal and mesophyll responses and are particularly relevant for bioengineering of CAM traits or bioenergy crops to exploit enhanced water-use efficiency and productivity on marginal land. With the increasing availability of powerful analytical tools and the emergence of new model systems for the study of the molecular basis of physiological traits in CAM plants, many exciting avenues for future research are open to intrepid investigators.

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Section: Stomatal Responses To External Stimulimentioning

confidence: 56%

“…1; Osmond, 1978). Stomatal conductance is typically highest during the dark period (Phase I), in association with nocturnal CO 2 assimilation by PEPC.…”

Section: Patterns Of Stomatal Conductancementioning

confidence: 99%

Section: Stomatal Responses To External Stimulimentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Stomatal Biology of CAM Plants

Males

Griffiths

2017

Plant Physiol.

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Fuels from Biomass

Klass

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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FUELS FROM BIOMASS. Projections indicate that biomass energy contribution will increase to over 4% of total U.S. primary energy consumption. Land‐ and waterbased vegetation, organic wastes, and photosynthetic organisms are categorized as biomass and are nonfossil, renewable carbon resources from which energy, eg, heat, steam, and electric power, and solid, liquid, and gaseous fuels, ie, biofuels, can be produced and utilized as fossil fuel substitutes. The capture of solar energy as fixed carbon in biomass via photosynthesis is the initial step in the growth of biomass. Human activity, particularly in the developing world, continues to make it more difficult to sustain the world's biomass growth areas. It has been estimated that tropical forests are disappearing at a rate of tens of thousands of hm 2 per year. The remaining carbon transport mechanisms on earth are primarily physical mechanisms. The great bulk of carbon is contained in the lithosphere as carbonates in rock and comprises 99.9% of the total carbon estimated to exist on the earth. Fossil fuel deposits are only about 0.05% of the total, and the nonfossil energy‐containing deposits make up the remainder, about 0.02%. Biomass carbon is a very small, but important, fraction of the total carbon inventory on earth. It has served as a primary energy source for the industrialized nations of the world; it continues to do so for developing countries. The utilization of biomass carbon as a primary energy source does not add any new carbon dioxide to the atmosphere; it is simply recycled between the surface of the earth and the air over a period of time that is extremely short compared to the recycling time of fossil‐derived carbon dioxide. The energy content of standing biomass carbon, ie, the above‐ground biomass reservoir that in theory could be harvested and used as an energy resource, is about 110 times the world's annual energy consumption. Biomass should be considered as a raw material for conversion to large supplies of renewable substitute fossil fuels. Under controlled conditions, dedicated biomass crops could be grown specifically for energy applications. Although relatively large areas are required, the use of land‐or freshwater‐based biomass for energy applications is still practical. Waste biomass is another large source of renewable carbon supply. Various processes can be used to produce energy or gaseous, liquid, and solid fuels from biomass and wastes. In addition, chemicals can be produced by a wide range of processing techniques. The manufacture of synfuels and energy products from virgin biomass requires that suitable quantities be grown, harvested, and transported to the conversion plant site. Many variables must be considered when selecting the $$$ for operation of a system. Several biomass species meet many idealized characteristics and appear to be quite suitable for energy applications. There are a number of important factors that relate to biomass production for energy applications. There is no biomass species grown and harvested in the United States specifically for conversion to biofuels, with the possible exceptions of feedstocks for fuel ethanol and a few tree plantations.

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Crassulacean Acid Metabolism

Lüttge

2008

Encyclopedia of Life Sciences

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Crassulacean acid metabolism (CAM) is a carbon dioxide acquisition, carbon dioxide transient storage and carbon dioxide concentrating mechanism of plants based on organic acid synthesis. In this variant of photosynthesis carbon dioxide can be fixed nocturnally in the dark and is used during the day for assimilation in the light. This has arisen polyphyletically many times during evolution. It is an ecophysiological adaptation that allows carbon dioxide acquisition with exceptionally economic use of water. It is regulated in a natural night/day rhythm but can also oscillate freely under the control of circadian biological clocks. Key concepts Metabolic mechanisms concentrating carbon dioxide internally in plants are important for photosynthesis at the low external carbon dioxide concentration in the present atmosphere. Rearranged internal management of available metabolic housekeeping functions can generate new metabolic options of adaptive value. Generation of isoforms of housekeeping enzymes can facilitate polyphyletic evolution of new metabolic pathways. Circadian oscillations can be controlled by different biological clocks, which are feedback related to each other and present in many copies. Flexibility in the expression of metabolic pathway variants facilitates adaptation under variable stress situations. Stress adaptation in plants is for survival and mostly not for high productivity.

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Crassulacean Acid Metabolism: A Curiosity in Context

Cited by 873 publications

References 0 publications

Stomatal Biology of CAM Plants

Stomatal Biology of CAM Plants

Fuels from Biomass

Crassulacean Acid Metabolism

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