Respiratory Patterns in Roots in Relation to Their Functioning (original) (raw)
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Specific root respiration of three plant species as influenced by storage time and conditions
Plant and Soil
Aims Specific root respiration (RRS) is a key root trait, determining i.e. nutrient foraging and uptake efficiencies. However, a considerable uncertainty exists regarding the effects of storage time and conditions on RRS measurements. Methods Fine root CO2 efflux rates of three plant types (tree seedling Carpinus betulus, legume Pisum sativum, grass Lolium perenne) were measured as depending on storage time (30–1440 min post-rinsing) and conditions (i.e. attached to plant, warm and cold water storage, and storage under dry conditions). Results Short-term storage conditions (30 min) had a significant effect on measured RRS rates, in specific, RRS rates of all three species were significantly lower under dry storage. Irrespective of plant species or temperature, storage of excised roots in water did not affect RRS for 300 min,. RRS measurements remained stable for 1 day if roots were stored cold. Conclusions Our results have important implications on measurement routines of RRS—a gene...
Photosynthesis, Carbohydrate Metabolism and Respiration in Leaves of Higher Plants
Advances in Photosynthesis and Respiration, 2000
The relationships between photosynthesis, carbohydrate metabolism and respiration in leaves of plants are reviewed. We first provide an overview of how mitochondrial respiration relies on, and responds to, the supply of photosynthetic products in the light. The pathways by which the various substrates (glycine, oxaloacetate, malate and/or pyruvate) enter the mitochondria and are oxidized, are discussed. We also provide an overview of the pathways of mitochondrial electron transport, with particular attention being paid to the non-phosphorylating alternative oxidase (AOX). We then discuss what is known about leaf respiration rates in light versus darkness (both consumption and release). The extent to which mitochondrial consumption continues in the light is highly variable, being inhibited, not affected or even stimulated in various reports. On the other hand, non-photorespiratory mitochondrial release (R) is invariably inhibited by light (5-80% inhibition). R is sensitive to the lowest irradiance values, and is inhibited rapidly. Three methods via which R in the light is measured are outlined and mechanisms via which light might inhibit R are discussed. The effect that light to dark transitions have on respiration are also discussed: we distinguish the initial, photorespiratory postillumination burst (PIB) from the post-illumination rise in respiration (LEDR, light-enhanced-dark-respiration) which occurs following the PIB. The chapter also considers the demand for mitochondrially-derived ATP for photosynthesis and carbohydrate metabolism and the potential role of respiration during over-reduction of the chloroplast is highlighted. Mitochondrial respiration appears to be critical for the provision of ATP necessary for energy demanding processes in the light. Moreover, there is growing evidence that respiration helps a plant cope with excess photosynthetic redox equivalents, which otherwise can result in photo-oxidative stress.
2008
• Root respiration is a major contributor to soil CO 2 efflux, and thus an important component of ecosystem respiration. But its metabolic origin, in relation to the carbon isotope composition (δ 13 C), remains poorly understood. • Here, 13 C analysis was conducted on CO 2 and metabolites under typical conditions or under continuous darkness in French bean (Phaseolus vulgaris) roots. 13 C contents were measured either under natural abundance or following pulse-chase labeling with 13 C-enriched glucose or pyruvate, using isotope ratio mass spectrometer (IRMS) and nuclear magnetic resonance (NMR) techniques. • In contrast to leaves, no relationship was found between the respiratory quotient and the δ 13 C of respired CO 2 , which stayed constant at a low value (c.-27.5‰) under continuous darkness. With labeling experiments, it is shown that such a pattern is explained by the 13 C-depleting effect of the pentose phosphate pathway; and the involvement of the Krebs cycle fueled by either the glycolytic input or the lipid/protein recycling. The anaplerotic phosphoenolpyruvate carboxylase (PEPc) activity sustained glutamic acid (Glu) synthesis, with no net effect on respired CO 2. • These results indicate that the root δ 13 C signal does not depend on the availability of root respiratory substrates and it is thus plausible that, unless the 13 C photosynthetic fractionation varies at the leaf level, the root δ 13 C signal hardly changes under a range of natural environmental conditions.
Regulation of Root Respiration and Sugar-Mediated Gene Expression In Plants
Current Science, 2000
The respiration rate of plant tissues is related to both substrate supply and demand for respiratory energy. At the biochemical level, it is considered to be regulated by the supply of adenosine diphosphate. In the whole plants, respiration rate is correlated with carbohydrate content suggesting control by substrates. There is evidence to support both the hypotheses, and they can be reconciled if the capacity of tissues for respiration can alter within a few hours and sucrose can control that capacity. Supplying exogenous sugars to the starved tissue not only increases the rate of respiration of that tissue but also leads to induction of enzymes which are involved in reversing the carbohydrate starvation-induced effects in plants. Expression of proteins and metabolic systems may be under the direct or indirect control of sugar. Sucrose or some product of its metabolism can control gene expression of these proteins, probably by increasing transcription.
Response of root respiration and root exudation to alterations in root C supply and demand in wheat
Plant and Soil, 2007
Rising atmospheric CO 2 concentrations have highlighted the importance of being able to understand and predict C Xuxes in plant-soil systems. We investigated the responses of the two Xuxes contributing to below-ground eZux of plant root-dependent CO 2 , root respiration and rhizomicrobial respiration of root exudates. Wheat (Triticum aestivum L., var. Consort) plants were grown in hydroponics at 20°C, pulse-labelled with 14 CO 2 and subjected to two regimes of temperature and light (12 h photoperiod or darkness at either 15°C or 25°C), to alter plant C supply and demand. Root respiration was increased by temperature with a Q 10 of 1.6. Root exudation was, in itself, unaltered by temperature, however, it was reduced when C supply to the roots was reduced and demand for C for respiration was increased by elevated temperature. The rate of exudation responded much more rapidly to the restriction of C input than did respi-ration and was approximately four times more sensitive to the decline in C supply than respiration. Although temporal responses of exudation and respiration were treatment dependent, at the end of the experimental period (2 days) the relative proportion of C lost by the two processes was conserved despite diVerences in the magnitude of total root C loss. Approximately 77% of total C and 67% of 14 C lost from roots was accounted for by root respiration. The ratio of exudate speciWc activity to CO 2 speciWc activity converged to a common value for all treatments of 2, suggesting that exudates and respired CO 2 were not composed of C of the same age. The results suggest that the contributions of root and rhizomicrobial respiration to rootdependent below-ground respiration are conserved and highlight the dangers in estimating short-term respiration and exudation only from measurements of labelled C. The diVerences in responses over time and in the age of C lost may ultimately prove useful in improving estimates of root and rhizomicrobial respiration.
Advances in Photosynthesis and Respiration, 2005
The scope of our series, beginning with volume 11, reflects the concept that photosynthesis and respiration are intertwined with respect to both the protein complexes involved and to the entire bioenergetic machinery of all life. Advances in Photosynthesis and Respiration is a book series that provides a comprehensive and state-of-the-art account of research in photosynthesis and respiration. Photosynthesis is the process by which higher plants, algae, and certain species of bacteria transform and store solar energy in the form of energy-rich organic molecules. These compounds are in turn used as the energy source for all growth and reproduction in these and almost all other organisms. As such, virtually all life on the planet ultimately depends on photosynthetic energy conversion. Respiration, which occurs in mitochondrial and bacterial membranes, utilizes energy present in organic molecules to fuel a wide range of metabolic reactions critical for cell growth and development. In addition, many photosynthetic organisms engage in energetically wasteful photorespiration that begins in the chloroplast with an oxygenation reaction catalyzed by the same enzyme responsible for capturing carbon dioxide in photosynthesis. This series of books spans topics from physics to agronomy and medicine, from femtosecond processes to season long production, from the photophysics of reaction centers, through the electrochemistry of intermediate electron transfer, to the physiology of whole orgamisms, and from X-ray christallography of proteins to the morphology or organelles and intact organisms. The goal of the series is to offer beginning researchers, advanced undergraduate students, graduate students, and even research specialists, a comprehensive, up-to-date picture of the remarkable advances across the full scope of research on photosynthesis, respiration and related processes. The titles published in this series are listed at the end of this volume and those of forthcoming volumes on the back cover.
Plant Respiration: Metabolic Fluxes and Carbon Balance
2017
This book series AdvAnces In PhotosynthesIs And ResPIRAtIon: Including Bioenergy and Related Processes provides a comprehensive and state-of-the-art account of research in photosynthesis, respiration and related processes. Virtually all life on our planet Earth ultimately depends on photosynthetic energy capture and conversion to energy-rich organic molecules. These are used for food, fuel, and fiber. Photosynthesis is the source of almost all bioenergy on Earth. The fuel and energy uses of photosynthesized products and processes have become an important area of study, and competition between food and fuel has led to resurgence in photosynthesis research. This series of books spans topics from physics to agronomy and medicine; from femtosecond processes through season-long production to evolutionary changes over the course of the history of the Earth; from the photophysics of light absorption, excitation energy transfer in the antenna to the reaction centers, where the highly-efficient primary conversion of light energy to charge separation occurs, through the electrochemistry of intermediate electron transfer, to the physiology of whole organisms and ecosystems; and from X-ray crystallography of proteins to the morphology of organelles and intact organisms. In addition to photosynthesis in natural systems, genetic engineering of photosynthesis and artificial photosynthesis is included in this series. The goal of the series is to offer beginning researchers, advanced undergraduate students, graduate students, andeven research specialists, acomprehensive, up-to-date picture of the remarkable advances across the full scope of research on photosynthesis and related energy processes. The purpose of this series is to improve understanding of photosynthesis and respiration at many levels both to improve basic understanding of these important processes and to enhance our ability to use photosynthesis for the improvement of the human condition.