Modelling the Components of Plant Respiration: Some Guiding Principles

Respiration is poorly represented in whole plant or ecosystemmodels relative to photosynthesis. This paper reviews the principlesunderlying the development of a more mechanistic approach tomodelling plant respiration and the criteria by which modelbehaviour might be judged. The main conclusions are as follows:(1) Models should separate C substrate from structure so thatdirect or indirect C substrate dependence of the componentsof respiration can be represented. (2) Account should be takenof the fact that some of the energy for leaf respiration isdrawn from the light reactions of photosynthesis. (3) It ispossible to estimate respiration associated with growth, nitratereduction, symbiotic N₂fixation, N-uptake, other ion uptakeand phloem loading, because reasonable estimates are availableof average specific unit respiratory costs and the rates ofthese processes can be quantified. (4) At present, it is lesseasy to estimate respiration associated with protein turnover,maintenance of cell ion concentrations and gradients and allforms of respiration involving the alternative pathway and futilecycles. (5) The growth-maintenance paradigm is valuable but‘maintenance ' is an approximate concept and there isno rigorous division between growth and maintenance energy-requiringprocesses. (6) An alternative ‘process-residual’approach would be to estimate explicitly respiratory fluxesassociated with the six processes listed in (3) above and treatthe remainder as a residual with a phenomenological ‘residual maintenance’ coefficient. (7) Maintenance or‘residual maintenance’ respiration rates are oftenmore closely related to tissue N content than biomass, volumeor surface area. (8) Respiratory fluxes associated with differentprocesses vary independently, seasonally and during plant development,and so should be represented separately if possible. (9) Anunforced outcome of mechanistic models should be a constrained,but non-constant, ratio between whole plant gross photosynthesisand respiration. Copyright 2000 Annals of Botany Company Respiration, photosynthesis, growth, maintenance, substrate, N uptake, nitrate reduction, symbiotic N₂fixation, phloem loading, model.     

Effect of Wind on Plant Respiration

Various plant species were placed in a 13.5 liter belljar equipped with a motor-driven fan directly above the plants. Air was continually circulated from the belljar through an infrared CO₂ analyzer at the rate of 1.5 1/min. Species tested included Triticum aestivum, Hordeum vulgare, Avena sativa, Zea mays, Sorghum vulgare, Phaseolus vulgaris, Glycine max, Pisum sativum, and Magnolia grandiflora. Increases in respiration of shoots or intact plants were detected at windspeeds of 3.6 m/s and above. All species responded in a similar fashion with increases in respiration of 20 to 40% being typical at a windspeed of 7.2 m/s which is similar to windspeeds under many natural conditions. The respiration rate returned to the initial rate within a short time after the wind had stopped. In Magnolia a sustained elevated respiration rate was measured over an exposure period of 3 hours to a wind velocity of 7.1 m/s. In some experiments flutter of the leaves was prevented but the respiration rate of bean and Magnolia was still elevated in the wind. This would suggest that the response is subcellular and not due to gross movement of the leaf itself. It is suggested that such an elevated respiration rate (maximum increase measured was 56%) might be expected to interfere with net assimilation and may be responsible for lower yields obtained in windy regions.     

Misconceptions About the Relation Between Plant Growth and Respiration

Abstract: The relation between plant growth rate and respiration rate is readily derived from the overall chemical reaction for aerobic metabolism. The derived relation can be used to show that separation of respiration into growth (g) and maintenance (m) components is not a useful concept. g and m cannot be unambiguously measured or defined in terms of biochemical processes. Moreover, because growth yield calculations from biochemical pathway analysis, from biomass molecular composition, from biomass heat of combustion, and from biomass elemental composition have not included all of the energy costs for biosynthesis, they are not accurate measures of the carbon cost for plant growth. Improper definitions of growth-respiration relations are impeding the use of physiological properties for prediction of plant growth as a function of environmental variables.     

Modelling the Dynamical Components of the Sugar Beet Crop

Many models have been constructed to describe the growth ofthe sugar beet crop up to harvesting. In general, these modelshave a complex physiological basis, requiring a large numberof parameters yet relying on empirical functions with no mechanisticbasis to partition assimilates within the crop. An importantfactor in considering the growth of the crop, both from an economicand environmental point of view, is the response of the cropto varying amounts of available nitrogen in the soil. In thispaper, a model is described for crop growth using soil nitrogencontent and solar radiation as driving functions. The parsimoniousapproach to construction resulted in a 14 parameter model, sevenof which are associated with the driving variables. This issubstantially fewer than for other crop models. The model containsa new dynamical way of describing partitioning of assimilatesbetween shoot, storage root and fibrous roots. The partitioningmodel is derived from observations on the effect of soil nitrogenon crop growth. Interception of light is determined by foliagecover, which makes the model suitable for use with data collectedfrom satellite imaging. The model fits well to three independentdata sets with estimated parameters lying within biologicallyreasonable bounds. The model is used to test the sensitivityof yield to changes in soil nitrogen. Modelling; partitioning; parameter estimation; sugar beet; Beta vulgarisL.; nitrogen; crop growth dynamics     

植物线粒体呼吸状态的研究方法及其在植物生物学中的应用

线粒体呼吸状态是指当线粒体中呼吸底物及ADP以不同浓度存在时线粒体的呼吸速率,它是用来研究线粒体功能的重要指标。本文结合我们的研究经验,详细阐述了线粒体呼吸状态的研究方法,介绍了该方法在分析线粒体电子传递链功能和氧化磷酸化活性中的应用,此外概述了线粒体呼吸状态的测定和分析方法在植物生理生态研究中的具体应用。     

The Pattern of Respiration Rate in the Vegetative Barley Plant

In two experiments with young barley plants, respiration rate,carbohydrate content and growth rate of the whole plant weremeasured. When 18-day-old plants were darkened the rate of respirationand the levels of soluble carbohydrate fell in parallel overthe following 30 h. When the dark respiration rate of plantswas followed from 7 to 24 days respiration rate and solublecarbohydrate levels did not change together, nor did the respirationrate (R) follow the empirical relationship with photosynthesis(P) and d. wt (W) R = aW + bP, suggested by McCree. Hordeum distichum L. (Lam), barley, respiration, carbohydrate content     

Regulation of Respiration and Fermentation to Control the Plant Internal Oxygen Concentration

Plant internal oxygen concentrations can drop well below ambient even when the plant grows under optimal conditions. Using pea (Pisum sativum) roots, we show how amenable respiration adapts to hypoxia to save oxygen when the oxygen availability decreases. The data cannot simply be explained by oxygen being limiting as substrate but indicate the existence of a regulatory mechanism, because the oxygen concentration at which the adaptive response is initiated is independent of the actual respiratory rate. Two phases can be discerned during the adaptive reaction: an initial linear decline of respiration is followed by a nonlinear inhibition in which the respiratory rate decreased progressively faster upon decreasing oxygen availability. In contrast to the cytochrome c pathway, the inhibition of the alternative oxidase pathway shows only the linear component of the adaptive response. Feeding pyruvate to the roots led to an increase of the oxygen consumption rate, which ultimately led to anoxia. The importance of balancing the in vivo pyruvate availability in the tissue was further investigated. Using various alcohol dehydrogenase knockout lines of Arabidopsis (Arabidopsis thaliana), it was shown that even under aerobic conditions, alcohol fermentation plays an important role in the control of the level of pyruvate in the tissue. Interestingly, alcohol fermentation appeared to be primarily induced by a drop in the energy status of the tissue rather than by a low oxygen concentration, indicating that sensing the energy status is an important component of optimizing plant metabolism to changes in the oxygen availability.Plants are obligate aerobic organisms, with oxygen being an essential substrate for mitochondrial energy production. However, the poor distribution efficiency for oxygen through root, tuber, seed, or stem tissue of various species results in steep drops of the internal oxygen concentration, ranging from values near above zero to just below 40% of air saturation (e.g. Armstrong et al., 1994; Geigenberger et al., 2000; Rolletschek et al., 2002; van Dongen et al., 2003, 2004; Vigeolas et al., 2003).These low levels of internal oxygen strongly affect plant metabolism. Several studies showed that energy-consuming metabolic pathways are adjusted to the actual oxygen availability (for review, see Geigenberger, 2003; Bailey-Serres and Voesenek, 2008). By saving energy, the plant decreases the demand for respiratory oxygen consumption that could help to postpone or even prevent the tissue from becoming anoxic. Indeed, it was observed that the metabolic flux through glycolysis slows down, respiratory oxygen consumption decreases, and adenylate levels drop in response to low internal oxygen (Geigenberger et al., 2000; Bologa et al., 2003). This inhibition of respiration is not easily explained by substrate limitation of cytochrome c oxidase (COX). First, the reduction of respiration becomes apparent already at oxygen concentrations around 20% of air saturation, whereas the K_m value for oxygen of COX lies around 0.05% of air saturation (which equals 0.14 μm under standard conditions; Drew, 1997). Second, the inhibition of respiration could be clearly distinguished from the induction of fermentation, which did not occur until oxygen fell to levels close to zero (Geigenberger, 2003).Based on these studies, it is reasonable to assume that a sensitive tuning mechanism must exist that allows the plant to regulate oxygen consumption while simultaneously preventing anoxia. However, hardly anything is known about the mechanism by which a plant induces adaptive responses to low oxygen (Bailey-Serres and Chang, 2005). Vice versa, comparably little is known about how metabolic activity affects the plant internal oxygen concentration. Previous studies focused on the effect that feeding of different sugars had on the respiration rate of tissue slices (Loef et al., 2001) or used transgenic approaches to stimulate metabolism by introducing a more energy-consuming route of Suc degradation via invertase in growing tubers (Bologa et al., 2003). In the latter case, respiration rates were increased and internal oxygen concentrations fell to very low levels that were close to zero. This shows that plant internal oxygen concentrations respond very sensitively to changes in metabolic activities. However, the underlying mechanism remains unclear.Glycolysis is part of the central backbone of primary carbohydrate metabolism and respiration. Pyruvate serves as a key metabolite linking glycolysis in the cytosol with mitochondrial respiration. Under aerobic conditions, pyruvate is transported into mitochondria and is oxidized through the tricarboxylic acid (TCA) cycle into organic acids and NADH. Moreover, pyruvate has regulatory potential, as it was shown that alternative oxidase (AOX) becomes more active in the presence of α-keto acids such as pyruvate (Millar et al., 1993, 1996; Vanlerberghe et al., 1995; Vanlerberghe and McIntosh, 1997), thus affecting the efficiency of ATP production per unit of oxygen being respired. Under oxygen-limiting conditions, pyruvate can either be converted into ethanol by pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) or to lactate by lactate dehydrogenase. Pyruvate also serves as a precursor for the synthesis of Ala via the reversible reaction catalyzed by Ala amino transferase, which was shown to play a crucial role in the rapid conversion of Ala to pyruvate during recovery from low-oxygen stress (Miyashita et al., 2007). Furthermore, pyruvate is the substrate of acetolactate synthase, which is the first enzyme committed to the biosynthesis of the branched-chain amino acids Val, Leu, and Ile. Inhibition of acetolactate synthase by the herbicide imazethapyr induces aerobic fermentation in plants (Gaston et al., 2002). Despite its central role in energy metabolism under both oxygen-rich and oxygen-depleted conditions, no investigations were made, to our knowledge, until now on the impact pyruvate has on the plant internal oxygen concentration.The aim of this study was to investigate the regulation of respiration and its relation to the plant internal oxygen concentration. To investigate this, we changed the oxygen concentration of the nutrient solution of hydroponically grown pea (Pisum sativum) plants and tested the influence of several sugars and organic acids. We measured root internal oxygen concentrations as well as the energy status of the tissue and related this to the rate of oxygen consumption by both the cytochrome c pathway and the AOX. The results are investigated in relation to the function and regulation of fermentative metabolism.     

Microbial and Root Components of Respiration of Sod-Podzolic Soils in Boreal Forest

The microbial contribution to the respiration of sod-podzolic soils has been estimated during two seasons (2012–2013) in boreal forest (Valdai district in Novgorod oblast, Russia) by a combination of methods of substrate induced respiration (SIR) and integration of components (IC). Despite the higher accuracy of SIR in estimating soil microbial respiration (R_mic), it is found that the combined application of these two methods results in a better correspondence of field experiments to the published data based on laboratory experiments. The contribution of microbial respiration differs between wooded and degraded sites. Hence, these sites should be investigated separately in upscaling studies of microbial respiration in soils of a boreal forest. The underestimation of microbial respiration should also be noted when using the IC method in field experiments. Among the main controls of R_mic are abiotic ones (soil temperature at a depth of 10 cm; month of the vegetation season), as well as the type of the mesohabitat. The seasonal dynamics of microbial respiration was related to the Selyaninov hydrothermal factor. Despite seasonal and cross-habitat differences in R_mic, it was specific for the particular type of soil and ecosystem.     

Plant Growth Analysis: Additive and Multiplicative Components of Growth

Three techniques used to investigate whole-plant growth areplant growth analysis, yield component analysis and demographicanalysis. Each subdivides growth into morphological or physiologicalcomponents. This paper derives several relationships which definethe contributions made by components to the performance of thewhole plant. For example, the additive contributions by differentplant parts to overall unit leaf rate may be determined. Also,for multiplicative components, the relative growth rate of yieldis the sum of the relative growth rates of yield components.The relationships developed here serve to link different approachesto growth analysis, and they are illustrated using data fromgrowth studies of bean and sunflower. Plant growth analysis, yield component analysis, demographic analysis, Phaseolus vulgaris L., Helianthus annus L.     

The Effect of L-Methionine on the Respiration of Plant Tissues1

The respiration of washed disks of storage tissue has been foundto be inhibited by L-methionine. The inhibitory effect of methionineappears to be exerted on the Krebs cycle and the inhibitionis reversed by dinitrophenol. The possibility that the increasedrespiration which occurs after washing disks of storage tissueis due to loss of methionine has been raised, and briefly discussedin relation to the tentative suggestion that methionine is acoupling agent between oxidation and phosphorylation.     

Effects of Cyanide and Ethylene on the Respiration of Cyanide-sensitive and Cyanide-resistant Plant Tissues

The effects of cyanide and ethylene, respectively, were studied on the respiration of a fully cyanide-sensitive tissue-the fresh pea, a slightly cyanide-sensitive tissue-the germinating pea seedling, and a cyanide-insensitive tissue-the cherimoya fruit. Cyanide inhibition of both fresh pea and pea seedling respiration was attended by a conventional Pasteur effect where fermentation was enhanced with an accumulation of lactate and ethanol and a change in the level of glycolytic intermediates indicative of the activation of phosphofructokinase and pyruvate kinase accompanied by a sharp decline in ATP level. In these tissues, ethylene had little or no effect on the respiration rate, or on the level of glycolytic intermediates or ATP. By contrast, ethylene as well as cyanide enhanced both respiration and aerobic glycolysis in cherimoya fruits with no buildup of lactate and ethanol and with an increase in the level of ATP. The data support the proposition that for ethylene to stimulate respiration the capacity for cyanide-resistant respiration must be present.     

Respiration Modelling and Hypothesis Testing with a Dynamic Model of Sugar Beet Growth

Respiration was predicted quantitatively during sugar-beet growthsimulations by assuming an intimate coupling to growth and maintenanceprocesses. Changes in the growth and maintenance respiratorycoefficients for successive simulations expressed alternativehypotheses regarding the nature of that coupling. Large differencesin yield, partitioning patterns, and the relative importanceof the growth and maintenance components were predicted in responseto changes in respiratory coefficients within the range consideredphysiologically realistic. Beta vulgaris L, sugar beet, respiration, growth yield, mathematical modelling     

Receptors and Signalling Components of Plant Hormones

Abstract

Recent advances in understanding plant hormonal signalling has resulted in the identification of a variety of signalling components including receptor kinases with homology to the bacterial two component system as well as serine/threonine kinases and protein phosphatases. In addition, the existence of MAP kinase pathways in plants indicates a similar role of these signalling cascades in the relay of exogenous signals into the nucleus as has been disclosed in animal cells. The emerging signalling pathways of the plant hormone abscisic acid and ethylene are presented.     

Metabolic Adaptations of Plant Respiration to Nutritional Phosphate Deprivation

Shoots of the lazy-2 (lz-2) gravitropic mutant of tomato (Lycopersicon esculentum Mill.) have a normal gravitropic response when grown in the dark, but grow downward in response to gravity when grown in the light. Experiments were undertaken to investigate the nature of the light induction of the downward growth of lz-2 shoots. Red light was effective at causing downward growth of hypocotyls of lz-2 seedlings, whereas treatment with blue light did not alter the dark-grown (wild-type) gravity response. Downward growth of lz-2 seedlings is greatest 16 h after a 1-h red light irradiation, after which the seedlings begin to revert to the dark-grown phenotype. lz-2 seedlings irradiated with a far-red light pulse immediately after a red light pulse exhibited no downward growth. However, continuous red or far-red light both resulted in downward growth of lz-2 seedlings. Thus, the light induction of downward growth of lz-2 appears to involve the photoreceptor phytochrome. Fluence-response experiments indicate that the induction of downward growth of lz-2 by red light is a low-fluence phytochrome response, with a possible high-irradiance response component.     

Modelling Water in Crops and Plant Ecosystems

A water submodel is described that is specifically designedfor use with plant growth simulators that represent internalplant substrates and variable shoot:root partitioning. The modelcalculates water flow from soil to root, root to shoot, andshoot to the atmosphere, for a closed-canopy situation. As presentedhere, the model has three state variables: the masses of waterin the soil, root and shoot, and represents the processes ofevapotranspiration, rainfall interception and evaporation fromthe canopy, and drainage. The Penman –Monteith equationis used for crop transpiration. The fluxes of water from soilto root, and root to shoot, are driven by water potential difference.Tissue water potential and its components are calculated fromtissue water content and other plant variables and parameters.The model is able to simulate osmoregulation and describes avariable relationship between tissue water potential, its componentsand relative water content, depending on growth conditions.The model has elsewhere been integrated with two plant ecosystemmodels: for grassland and forest. The specific implementationand simulations given are for the Hurley pasture model (Thornleyand Verberne, 1989), a temperate grass vegetative growth model.The model gives reasonable predictions for diurnal changes inwater potential, drying-down behaviour and other quantitieswithin the scope of the model. Simulation; model; water relations; crop growth; grass     

Nitrogen Metabolism, Respiration, and Growth of Cultured Plant Tissue

Critical examination of the amino-acid composition of proteinsin fast-growing and slow-growing tissues reveals only very 8maUdifferences, indicating that some factor other than the amino-acidcomplement is responsible for, or reflects, the great increasein the mass of protein in the fast-growing tissues. Increases in fresh weight and total protein are exactly parallel,indicating that water uptake is an active process associatedwith growth. Respiration, on the other hand, increases far morein the fast-growing over the slow-growing tissues than doestotal protein. A given amount of protein in the fast-growingtissue will support a much greater respiration rate than thesame amount in slow-growing tissue. The incorporation of radioactivity into amino-acids of the proteinin4icates that there are two distinct types: those in whichincorporation is increased in fast-growing tissue much morethan the total protein, and to the same ezte as respiration(notably glutarnic acid, aspartic acid, and threonine); andthose in which the increased incorporation is much nafler, slightlyless than total protein (notably proline and hydroxyproline).It is concluded that there are two n protein fractions: the‘active’ moiety, which is undergoing rapid breakdownd resynthesis, giving rise to much of the CO through oxidationof its residues; a the ‘inactive’ moiety, whichonce synthesized is not reutilized or broken down. It is theformer, or ‘active‘ protein whose synthesis is greatlyincreased in the fast. growing tissues, and it is the pace,rather than the kind, of reactions which differ entiates betweenthe fast- and slow-growing tissues. The entire experimental data are discussed with reference toa number of cur rent theories and investigations. A number ofexperimental observations are noted which admit of interpretationalong the lines here developed.     

Estimating the Bioenergetic Cost of a Developing Kiwifruit Berry and its Growth and Maintenance Respiration Components

A response surface was developed by regression analysis to quantifythe seasonal respiratory losses by a kiwifruit [Actinidia deliciosa(A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv.Hayward] berry growing in Fresno, CA. The equation of the surfacewas LNRESP = 1·622 + 0·0697 x TEMP –0·0472x DAY + 0·000165 x DAYSQ, where LNRESP is the naturallogarithm of the respiration rate (nmol CO₂ g d. wt^–1s^–1), TEMP is fruit temperature (°C), DAY is the numberof days after flowering, and DAYSQ is the square of the numberof days after flowering. Respiratory losses for a fruit witha final dry mass of 18·5 g were calculated to be 5·57and 5·92 g glucose per fruit per season in 1985 and 1986,respectively. Maintenance respiration was estimated to be 2·84and 3·19 g glucose per fruit per season for 1985 and1986, respectively. The total calculated bioenergetic cost ofkiwifruit berry growth and respiration was 25·25 and25·60 g glucose per fruit per season for 1985 and 1986,respectively. Respiratory losses, expressed as a proportionof the total carbohydrate required for fruit growth, were significant(mean 22·6%). The cost of fruit growth was estimatedto be very similar for two cooler sites (Davis and Watsonville)but estimates of maintenance respiration based on Fresno fruitrespiration data were unrealistically low for the Watsonvillesite. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson var. deliciosa cv. Hayward, kiwifruit, growth respiration, maintenance respiration, bioenergetic costs, model