Growth and Maintenance Respiration: a Reconciliation of Thornley's Model and the Traditional View

There are two competing views of the growth and maintenanceaspects of plant respiration: a traditional view based on growthanalysis which relates respiration to whole plant dry weightand a differential equation formulation which distinguishesbetween storage material that may be used for growth, non-degradablestructure, and degradable structure that degrades at some rateand may be recycled. It is shown how and under what conditionsthese two mathematical models may be reconciled. Suggestionsare made for improving both models. growth, respiration, maintenance respiration, mathematical model     

Growth and Maintenance Respiration in Whole Plants, Tops, and Roots of Lolium multiflorum

Continuous measurements of CO₂-exchange were separately carried out on tops and roots of small swards of Lolium multiflorum grown in nutrient solution in growth chamber during 3–4 weeks. From these measurements, a daily carbon balance and accumulated dry matter could be established. The data were used to distinguish between two components of respiration, one proportional to growth or photosynthesis (growth respiration), the other proportional to plant dry weight (maintenance respiration). The separation of respiration in the two components was made by multiple regression analyses with daily photosynthesis or growth rate and accumulated dry matter as the independent variables. To ensure independency between the independent variables during the growth period, photosynthesis was varied by application of alternate three-day periods of high and low irradiance. From the two regression coefficients, the efficiency of converting assimilates into constructive growth (Y_G) and the maintenance coefficient (M) could be derived. Three experiments with varying length of photoperiod and dark period were carried out. The analyses were carried out for whole-plant respiration, respiration of tops and respiration of roots separately. Growth respiration for whole plants as well as for tops and for roots was lower — and hence the efficiencies higher — the longer the photoperiods were. Growth respiration and maintenance respiration were higher for roots than for tops. The high rate of root respiration may originate from release of HCO₃^? in exchange for NO₃^?. The parameters found can be utilized quantitatively in computer models of crop photosynthesis and respiration.     

Respiration of Senecio Shoots: Inhibition during Photosynthesis, Resistance to Cyanide and Relation to Growth and Maintenance

Respiration and dry matter producation were measured in shoots of senecia aquaticus Hill, which is flood tolerant and in shoots of S. jacobaea L., which is flood- sensitive. Both species were grown in culture solutions of high and of low oxygen concentration Growth of food of S. jacobaca was unaffected by a low oxygen supply bur growth of S. jacobaca was severly hampered by a low oxygen concentration in the root medium. Kinetic data about the rate of apparent photosynthesis at low oxygen conetration and different carbon dioxide concentrations indicated that at light saturation respiration was strongly repressed during photosynthesis. Shoot growth respiration, i.e. the amount of carbon dioxide produced for synthesis of shoot dry, matter appeared to be absent on S. jacobaea and to be very low (13.mg CO₂/g dry shoots) in S. aquaticus. In comparison with values prepiration rate was 2.8. 2.0. 1.5 and 1.3mg CO₂/h.g dry shoots in aerobically and anaerobically growth S. jacobaea and in aerobically and anaerobically growth S. aquabaea respectively. These values were also low in comprision with values previously found for roots of the same species. Shoot dark respiration on S. aquaticus was inbihitedd by a com bination on CN and salicylhydroxamic acid (SHAM), but not by application on one of these inhibitors alone. It was therefore concluded that an alternative oxidative pathway was present but not active in shoots of S. aquaticus. In the absence of inhibited of the cylochorome pathway. The low value of growth respiration and maintenance respiration rate in the shoots as compared with those in the roots of the investigated Sencio species are discussed in relation to the activity of the alternative oxidative pathway and to the possibilbity of a direct supply of ATP by photosynthesis intead of respiratory meta bolism.     

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     

Energy, Respiration, and Growth in Plants

The energy relations and heat production during plant growthare analysed in terms of respiration, dry weight, and growth.Wastage respiration and its relationship to this analysis arediscussed The results of microcalorimetric experiments on wheatseedlings are analysed and interpreted.     

Maintenance Respiration of Oryza sativa Leaves at Different Growth Stages as Influenced by Nitrogen Supply

Maintenance respiration rate, R_M, irrespective of growth stages, increased with increase in nitrogen supply. The R_M increased almost in proportion with net photosynthetic rate, P_N, and biomass production during early growth stages, while it declined after anthesis. Significant positive correlation was observed between biomass production and P_N at all growth stages except tillering. Though R_M was positively correlated with biomass production during early growth stages, it was negatively correlated with the rate of increase in shoot biomass after flowering, which could indicate a possibility to identify certain cultivars endowed with low maintenance expenses despite building up biomass.     

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.     

Growth Respiration of a Flood-Tolerant and a Flood-Intolerant Senecio Species: Correlation between Calculated and Experimental Values

Root growth respiration of Senecio aquaticus Hill (flood-tolerant) and Senecio jacobaea L. (flood-sensitive) was calculated, assuming different P: O ratios. The growth respiration values were calculated on the basis of the chemical composition of root and shoot dry matter, in combination with published data on the energy costs of biosynthetic and transport processes. The comparison between calculated and experimental values suggests a relatively low efficiency of ATP utilization in the roots of the flood-tolerant species. Root growth respiration of S. congestus (R.Br.)DC., which is also flood-tolerant, and Plantago lanceolata L. were also determined. The data showed that not all the flood-tolerant species investigated had high root growth respiration values. An “overflow model’ is proposed to explain observed differences in root growth respiration between species.     

The Tomato Fruit: Import, Growth, Respiration and Carbon Metabolism at Different Fruit Sizes and Temperatures

Measurements of a complete carbon balance sheet over a 48 hperiod for growing tomato fruits at different fruit sizes andtemperature have been carried out. The rates of carbon import,respiration, and growth have been calculated and related toeach other and to the levels of certain carbon metabolites inthe fruit. It was found that there is an excellent linear relationshipbetween the import rate and the sucrose level in the fruit,consistent with the hypothesis that, for the tomato fruit, carbonflows down the sucrose concentration gradient at a rate proportionalto the gradient. This agrees with the findings of Mason andMaskell in cotton. Moreover, the resistance to transport wasrelatively independent of fruit size and temperature. The usualanalysis of respiration in terms of growth and maintenance componentsallowed the determination of conversion efficiencies and maintenancecoefficients for different fruit sizes and temperatures. Asobserved by other authors with other plants, the growth conversionefficiencies were temperature-independent, whereas the maintenancecoefficients were strongly temperature-dependent. The overallconversion efficiency was optimum at 25°C. The specificgrowth rate and the starch level in the tomato fruit were foundto be related.     

Growth Rate, Photosynthesis and Respiration in Relation to Leaf Area Index

This work examined three possible explanations of growth rateresponses to leaf area index (LAI) in which growth rate perunit of ground area (crop growth rate, CGR) increased to a plateaurather than decreasing above an optimum LAI at which all lightwas intercepted. Single leaf photosynthetic measurements, andwhole plant 24 h photosynthesis and respiration measurementswere made for isolated plants and plants in stands using Amaranlhushybridus, Chenopodium album, and two cultivars of Glycine maxgrown at 500 and 1000 µimol m^–2 S^–1 photosyntheticphoton flux density at 25 °C. CGR, relative growth rate(RGR), and LAI were determined from 24 h carbon dioxide exchangeand leaf area and biomass measurements. Respiration increasedrelative to photosynthesis with crowding in A. hybridus andthere was an optimum LAI for CGR. In contrast, the ratio ofrespiration to photosynthesis was constant across plant arrangementin the other species and they had a plateau response of CGRto LAI. Neither increased leaf photosynthetic capacity at highLAI nor a large change in biomass compared to the change inLAI could account for the plateau responses. It was calculatedthat maintenance respiration per unit of biomass decreased withdecreasing RGR in C. album and G. max, but not A. hybridus,and accounted for the plateau response of CGR to LAI. Sincesimilar decreases in maintenance respiration per biomass atlow RGR have been reported for several other species, a constantratio of respiration to photosynthesis may occur in more speciesthan constant maintenance respiration per unit of biomass. Amaranlhus hybridus L., Chenopodium album L., Glycine max L Merr, soybean, photosynthesis, respiration, growth, leaf area index     

Waste Water Derived Electroactive Microbial Biofilms: Growth,Maintenance, and Basic Characterization

The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (j_max) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (E_p), peak current density (j_p), formal potential (E^f) and peak separation (ΔE_p). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis.     

Defoliation in White Clover: Nodule Metabolism, Nodule Growth and Maintenance, and Nitrogenase Functioning During Growth and Regrowth

In two experiments, the functioning and metabolism of nodulesof white clover, following a defoliation which removed abouthalf the shoot tissue, were compared with those of undefoliatedplants. In one experiment, the specific respiration rates of nodulesfrom undefoliated plants varied between 1160 and 1830 µmolCO₂ g^–1h^–1, of which nodule ‘growth and maintenance’accounted for 22 ± 2 per cent, or 27 ± 3.6 percent, according to method of calculation. Defoliation reducedspecific nodule respiration and nodule ‘growth and maintenance’respiration by 60–70 per cent, and rate of N₂ fixationby a similar proportion. The original rate of nodule metabolismwas re-established after about 5 d of regrowth; during regrowthnodule respiration was quantitatively related to rate of N₂,fixation: 9.1 µmol CO₂ µmol^–1N₂. With the possible exception of nodules examined 24 h after defoliation,the efficiency of energy utilization in nitrogenase functioningin both experiments was the same in defoliated and undefoliatedplants: 2.0±0.1 µmol CO₂ µmol^–1 C₂H₄;similarly, there was no change in the efficiency of nitrogenasefunctioning as rate of N₂ fixation increased with plant growthfrom 1 to 22 µmol N₂ per plant h^–1. Exposure of nodulated white clover root systems to a 10 percent acetylene gas mixture resulted in a sharp peak in rateof ethylene production after 1.5–2.5 min; subsequently,rate of ethylene production declined rapidly before stabilisingafter 0.5–1 h at a rate about 50 per cent of that initiallyobserved. Regression of ‘peak’ rate of ethyleneproduction on rate of N₂ fixation indicated a value of 2.9 µmolC₂H₄ µmol^–1 N₂, for rates of N₂ fixation between1 and 22 µmol N₂ per plant h^–1. The relationshipsbetween nitrogenase respiration, acetylene reduction rates andN₂ fixation rates are discussed. Trifolium repens, white clover, defoliation, nodule respiration, N₂, fixation, nitrogenase     

Root Distribution, Growth, Respiration, and Hydraulic Conductivity for Two Highly Productive Agaves

Cultivated Agave mapisaga and A. salmiana can have an extremelyhigh above-ground dry-weight productivity of 40 Mg ha^–1yr^–1. To help understand the below-ground capabilitiesthat support the high above-ground productivity of these Crassulaceanacid metabolism plants, roots were studied in the laboratoryand in plantations near Mexico City. For approximately 15-year-oldplants, the lateral spread of roots from the plant base averaged1.3 m and the maximal root depth was 0.8 m, both considerablygreater than for desert succulents of the same age. Root andshoot growth occurred all year, although the increase in shootgrowth at the beginning of the wet season preceded the increasein growth of main roots. New lateral roots branching from themain roots were more common at the beginning of the wet season,which favoured water uptake with a minimal biomass investment,whereas growth of new main roots occurred later in the growingseason. The root: shoot dry weight ratio was extremely low,less than 0.07 for 6-year-old plants of both species, and decreasedwith plant age. The elongation rates of main roots and lateralroots were 10 to 17 mm d^–1, higher than for various desertsucculents but similar to elongation rates for roots of highlyproductive C₃ and C₄ agronomic species. The respiration rateof attached main roots was 32 µmol CO₂ evolved kg^–1dry weight s^–1 at 4 weeks of age, that of lateral rootswas about 70% higher, and both rates decreased with root age.Such respiration rates are 4- to 5-fold higher than for Agavedeserti, but similar to rates for C₃ and C₄ agronomic species.The root hydraulic conductivity had a maximal value of 3 x 10^–7ms^–1 MPa^–1 at 4 weeks of age, similar to A. deserti.The radial hydraulic conductivity from the root surface to thexylem decreased and the axial conductivity along the xylem increasedwith root age, again similar to A. deserti. Thus, although rootsof A. mapisaga and A. salmiana had hydraulic properties perunit length similar to those of a desert agave, their highergrowth rates, their higher respiration rates, and the greatersoil volume explored by their roots than for various desertsucculents apparently helped support their high above-groundbiomass productivity Key words: Crassulacean acid metabolism, productivity, root elongation rate, root system, water uptake     

Effect of Temperature on Growth, Respiration, and Nutrient Regeneration by an Omnivorous Microflagellate

The effect of temperature on the rates and extent of carbon and nitrogen cycling by the heterotrophic microflagellate Paraphysomonas imperforata (diameter, 7 to 12 μm) fed with the diatom Phaeodactylum tricornutum was investigated over an ecologically pertinent temperature range (14 to 26°C). All physiological rates investigated increased with increasing temperature. Q₁₀ values were similar for all rate changes and were comparable to those which have been reported for other protozoa. In contrast to all rates, microflagellate gross growth efficiency and cell volume were unaffected by temperature. Decreases in the concentrations of particulate carbon and particulate nitrogen from grazed diatom cultures also were similar when summed over the entire growth phase of the microflagellate population. Therefore, the proportions of ingested carbon and nitrogen which were incorporated or remineralized by the microflagellate were independent of temperature between 14 and 26°C. At temperatures above 18°C, growth rates of P. imperforata were greater than the maximum growth rates reported for most phytoplankton. We conclude that the impact of P. imperforata on natural phytoplankton communities is not controlled by temperature above 18°C but may be affected by the rate at which zooplankton or microzooplankton prey on the microflagellate, as well as the inability of the microflagellate to graze efficiently when phytoplankton are present at low cell densities.     

Calculation of Growth Yield, Growth Respiration and Heat Content of Grain Sorghum from Elemental and Proximal Analyses

Elemental and proximate organic compositions were determinedfor biomass samples from two cultivars of grain sorghum [Sorghumbicolor (L.) Moench] grown in the field with two levels of nitrogensupply. Several methods of calculating the costs of biomasssynthesis were compared. Penning de Vries' Production Values(PV), based on proximate analyses and Glucose Values (GV) calculatedfrom elemental analyses or heats of combustion, yielded similartrends in response to variation in nitrogen supply and plantage but were not different for the two cultivars. The correctnessof the GV calculations was confirmed through comparisons ofmeasured and predicted heats of combustion. The ratio of PV/GV,representing the growth efficiency (E) of the samples, was closeto constant (0·84 + 0·02). Since PV is an estimateof the true growth yield, the constant growth efficiency allowsthe estimation of that value from elemental analyses. The truegrowth yield of the sorghum crops ranged from 0·73 to0·74 g biomass g^–1 glucose when grown with adequateN and from 0·77 to 0·78 with low N supply. Overthe crop cycle, with adequate N, 0·19 of the C used ingrowth processes was calculated as lost in growth respiration;with limited N, 0·17 was lost. Sorghum bicolor (L.) Moench, glucose equivalent, production value, growth efficiency nitrogen     

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     

Oxygen Control of Reproductive Growth: Possible Mediation via Dark Respiration

The rates of dark respiration of Glycine max leaves, pods, andseeds, are shown to be positively related to O₂ concentration([O₂]) between 2 and 21 per cent. It is suggested that the reporteddepression of seed growth, due to subatmospheric concentrationsof O₂ is caused simply by depression of respiration and thatit is not necessary to postulate a new control mechanism mediatedby [O₂].     

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.