Growth and Biomass Allocation, with Varying Nitrogen Availability, of Near-isogenic Pea Lines with Differing Foliage Structure

The single-gene mutation afila in pea (Pisum sativum L.) resultsin the replacement of proximal leaflets with branched tendrils,thereby reducing leaf area. This study investigated whethertheafila line could adjust biomass partitioning when exposedto varying nutrient regimes, to compensate for reduced leafarea, compared with wild-type plants. Wild-type and afila near-isogeniclines were grown in solution culture with nitrate-N added toinitially N-starved seedlings at relative addition rates (R_N)of 0.06, 0.12, 0.15 and 0.50 d^-1. The relative growth rate (R_W)of the whole plants closely matched R_Nat 0.06 and 0.12 d^-1,but higher R_Nresulted in a slightly higher growth rate. At agiven R_N, the wild-type line had lower plant nitrogen statusthan the afila line. R_Wof the roots of the afila line was lessthan R_Wof the roots of the wild-type at the three higher ratesof N supply despite a greater accumulation of N in the rootsof the afila plants. Consequently, plant nitrogen productivity(growth rate per unit nitrogen) was lower for afila. Dry matterallocation was strongly influenced by nitrogen status, but nodifferences in shoot–root dry matter allocation were foundbetween wild-type and afila with the same plant N status. Theseresults imply that decreased leaf area as a result of the single-genemutation afila affects dry matter allocation, but only accordingto its effect on the nitrogen status. Copyright 2000 Annalsof Botany Company Pisum sativum, pea, nitrogen limitation, growth, shoot–root allocation, relative growth rate, nitrogen productivity, isolines     

Theoretical Basis of Protocols for Seed Storage III. Optimum Moisture Contents for Pea Seeds Stored at Different Temperatures

In previous work, we demonstrated that there was an optimummoisture level for seed storage at a given temperature (Vertucciand Roos, 1990), and suggested, using thermodynamic considerations,that the optimum moisture content increased as the storage temperaturedecreased (Vertucci and Roos, 1993b). In this paper, we presentdata from a two year study of aging rates in pea (Pisum sativum)seeds supporting the hypothesis that the optimum moisture contentfor storage varies with temperature. Seed viability and vigourwere monitored during storage under dark or lighted conditionsat relative humidities between 1 and 90%, and temperatures between-5 and 65°C. The optimum moisture content varied from 0·015g H₂O g^-1 d.wt at 65°C to 0·101 g H₂O g^-1 d.wt at15°C under dark conditions and from 0·057 at 35°Cto 0·092 g H₂O g^-1 d.wt at -5°C under lighted conditions.Our results suggest that optimum moisture contents cannot beconsidered independently of temperature. This conclusion hasimportant implications for 'ultra-dry' and cryopreservationtechnologies.Copyright 1994, 1999 Academic Press Seed storage, seed aging, seed longevity, water content, temperature, glass, desiccation damage, ultradry, Pisum sativum L., pea, cryopreservation     

Functional Significance of Acid Phosphatase Distribution During Embryo Development in Pisum sativum L

The distribution of P₁, ester P and acid-insoluble nucleic acidP has been studied in relation to acid phosphatase activity(EC 3. 1. 3. 2) in the component parts of developing pea seeds(Pisum sativum L.). Despite the favourable pH of the liquidcontents of the embryo sac (pH 5.5), only very low acid phosphataseactivity was detected in this fluid (c. 0.01 units per seed).Potential substrates for phosphatase action were in fact absentfrom the secretion, the only form of P present being P_i, inconcentrations up to 8 mM. The data support the hypothesis thatthe high acid phosphatase activities which develop in the seed-coatsare involved in regulating the supply of P as P₁ to the developingembryo. Pisum sativum L., pea, embryo development, acid phosphatase, phosphorus, seed-coats, seed development     

Comparison of [14C]oryzalin Uptake in Root Segments of a Sensitive and a Resistant Species

Uptake of the dinitroaniline herbicide oryzalin (3,5-dinitro-N⁴,N⁴-dipropylsulfamlamide) and its effect on root growth werestudied using 5 mm corn (Zea mays L.) and pea (Pisum sativum)root apices. Pea root growth was much less susceptible to oryzalinthan corn root growth. Uptake studies showed that pea root apicesalso accumulated much less [¹⁴C]oryzalin and had a lower bindingaffinity for this herbicide. [¹⁴C]oryzalin was not metabolizedin root apices from either species. Thus, the differential susceptibilityto oryzalin in the case of corn versus pea can be explained,at least in part, by differences in oryzalin uptake and accumulationby roots. Oryzalin, dinitroaniline herbicides, Zea mays, Pisum sativum     

Validation of the Principal Axis Model (PAM) and its Application to Genotype Selection in Field Pea (Pisum sativum L.) Crops

The principal axis model (PAM) uses a principal axis and anellipse to characterize the variation in the relationship betweenthe seed (SWT) and plant (PWT) weights of individual plantswithin a crop. The theoretical linkage between the magnitudeand variability of plant harvest index (PHI), and thereforeseed yield per unit area, and changes in the components of thePAM was examined using data from four field pea (Pisum sativumL.) genotypes sown at 9, 49, 100, 225 and 400 plants m^-2. Astrong linear relationship (R ²>93.8%) between SWT and PWTand a negative SWT-axis intercept were confirmed for all crops.Analyses indicated that decreased variability of PHI withina crop would result from selection to: (a ) increase the SWT-axisintercept of the PAM; (b ) increase the slope of the PAM; (c) optimize the ellipse location; and (d ) minimize the deviationaround the principal axis. The first three methods were usedto explain yield differences (P <0.05) among genotypes ofdifferent populations. A potential strategy for single plant selection based on thePAM is proposed. This may enable early generation (F₄) selectionof small, high performing plants that may be ideal crop ideotypes.A theoretical example of the strategy is presented, with differencesamong selections based on the PAM, SWT or harvest index highlighted. Field pea(Pisum sativum L.); genetic harvest index; minimum plant weight; plant harvest index; principal axis model; plant population; seed weight; selection criteria     

Internode Length in Pisum. A New Allele at the le Locus

In Pisum sativum L. a third, more severe, allele at the internodelength locus le is identified and named le^d. Plants homozygousfor le^d possess shorter internodes and appear relatively lessresponsive to GA₂₀ than comparable le (dwarf) plants. Gene le^dmay act by reducing the 3ß-hydroxylation of GA₂₀ tothe highly active GA₁ more effectively than does gene le. Theresults indicate that le is a leaky mutant and therefore thatendogenous GA₁ influences internode elongation in dwarf (le)plants. Pisum sativum, peas, internode length, genetics, gibberellin, dwarf elongation     

Comparative Studies of Acid Glycosidases from Three Legumes

The major isoenzymes of -mannosidase (EC 3.2.1.24 [EC] ) and ß-galactosidase(ECf 3.2.1.23 [EC] ) have been separated from cotyledons of gardenpea, Pisum sativum L. (Vicieae), chick pea, Cicer arietinumL. (Cicereae), and cowpea, Vigna unguiculata (L.) Walp. (Phaseoleae).Some of their properties have been determined, including pHoptima, K_m values for p-nitrophenyl glycosidc substrates, andthe effects of several inhibitors. Swainsonine, an indolizidinealkaloid, was the most effective inhibitor of mannosidase 1,with I₃₀ values of 5.6 x 10^–8 M (cowpea), 1x 10^–7M (chick pea) and 2.9 x 19^–7 M (pea). The most effectiveinhibitor of ß-galactosidase 2 from all sources wasD-galactonic acid-1,4-lactonwe (-lactone), with K_i values rangingbetween 3.0 and 3.9x 10^–3 M. An inhibitor of the E. coliß-galactosidose, p-aminophenyl thio-ß-D-galactopyranoside,did not inhibit any of the legume ß-galctosidases;rather it enhanced the activites of the enzymes from chick peaand cowpea cotyledons. Etiolated hull and seed tissues frompea pods developing in darkness contained similar acid glycosidaseactivities to normal green tissues, thus the chloroplast isan unlikely location for ß-galactosidase 2. The majorß-galactosidasesdetected with an indigogenic substrate (5-bromo-4-chloro-3-indoxyl-ß-D-galactopyranoside)following gel electrophoresis of extracts from pea hull, seedcoats and cotyledons appeared to be different from ß-galactosidase2. Acid glycosidase, cotyledon, isoenzyme, -lactone, legume, swainsonine     

Glycosidases from Cotyledons of Pisum sativum L.

-Mannosidase and ß-N-acetylglucosaminidase were purifiedfrom extracts of cotyledons of germinating Pisum sativum L.A 13-fold purification of a-mannosidase free from ß-N-acetylglucosaminidaseactivity was achieved by precipitation in ammonium sulphate,column chromatography on DEAE-cellulose, and treatment with2 M pyridine. ß-N-Acetylglucosaminidase was purified200-fold by the use of (NH₄)₂SO₄, and chromatography on ConcanavalinA¹-Sepharose and Sephacryl-200. This preparation showed no measurablecontamination by -mannosidase activity. Both glycosidases appearto be glycoproteins and demonstrate optimal activity at pH valuesof 4.0–4.5. Both glycosidases appear to have very similarmolecular weights, with -mannosidase being slightly larger thanß-N-acetylglucosaminidase. An extensive search forthe activity of aspartylglycosylamine amido hydrolase in peacotyledons proved unsuccessful.     

Turnover of Storage Protein in Seeds of Soya Bean and Pea

We were interested in determining whether the low protein contentof pea seeds (Pisum sativum L.) as compared to soya bean seeds(Glycine max L. Merrill) might be due to faster degradationof the pea storage proteins during development of the seed.Pea and soya bean cotyledons were subjected to a ‘pulse-chase’experiment using [³H]glycine in in-vitro cultures. In peas,legumin had a half-life of 146 days, while vicilin had a half-lifeof 39 days. There was no measureable degradation of soya beanstorage proteins. Even with the pea storage proteins, the half-liveswere so much longer than the maturation time of seeds that degradationof storage proteins could not account for the lower proteincontent of peas as compared to soya beans. The validity of theseresults was indicated by the finding that non-storage proteinshad much shorter half-lives and that omission of a carbon ora nitrogen source greatly accelerated degradation. Labelledglycine was found to be a good probe for protein turnover studiesbecause it was very rapidly metabolized. Glycine max L. Merrill, soya bean, Pisum sativum, L. pea, protein turnover, storage proteins, legumin, vicilin     

Buckminsterfullerene (C-60 Carbon Allotrope) Inhibits Ethylene Evolution from 1-Aminocyclopropane-1-carboxylic acid (ACC)-treated Shoots of Pea (Pisum sativum), Broadbean (Vicia faba) and Flowers of Carnation (Dianthus caryophyllus)

When applied either in the form of a colloidal solution or inliposomes, buckyballs (C-60—buckminsterfullerene) markedlyreduced ethylene evolution from cut carnation (Dianthus caryophyllus)flowers, as well as pea (Pisum sativum) and broadbean (Viciafaba) foliage treated with ethylene precursor l-aminocyclopropane-l-carboxylicacid (ACC). The liposome preparation was approximately twiceas effective as colloidal solutions. Moreover, upon being incubatedin a closed atmosphere with ethylene, buckyballs induced a significantdepletion of ambient ethylene which was temperature and C-60—concentrationdependent. This mode of C-60 action is attributed to ethyleneadsorption stemming from the vast C-60 surface area, calculatedto be 1317 m² g_-1, and the affinity of its carbon atoms forthe component in the ethylene double bond.Copyright 1993, 1999Academic Press Dainthus caryophyllus, Pisum sativum, Vicia faba, adsorption, ethylene, fullerene     

Temperature Response of Early Foliar Expansion of Potato and Wheat

We studied the course of early leaf area expansion and specificleaf area (S_LA) in potato (Solanum tuberosum L.) and wheat (Triticumaestivum L.) genotypes and tested whether air temperature explainsdifferences in these courses within different environments.Such knowledge can be used to improve crop growth modelling.The relative rate of leaf area expansion (R_L) of potato andwheat decreased with thermal time, but was nearly linear upto a leaf area index (L) of 1.0. TheR_L (L < 1; mean: 17.9x 10^-3°C^-1 d^-1) of potato showed an interaction betweengenotype and environment, and varied with year. TheR_L (L <1; mean: 7.1 x 10^-3°C^-1 d^-1) of winter wheat was lower thanthat of spring wheat (mean: 10.9 x 10^-3°C^-1 d^-1), and bothvaried with year. S_LAof potato increased nearly linearly withthermal time from 5 to 15 m² kg^-1at 50% emergence, to 20 to25 m² kg^-1at 155°Cd, and then decreased slightly. The S_LAofboth winter and spring wheat began at 16 to 23 m² kg^-1and inmost cases increased slightly with thermal time. In potato,regression parameters of S_LAwith thermal time were affectedby environment (management conditions and year) and genotype;in wheat they were affected by environment (year and site).Treatment effects on R_Lof potato were not correlated with thoseon S_LA , and were only partly correlated for wheat. Thereforewe conclude that the early foliar expansion of potato is associatedwith a strong increase in S_LA , and not so for wheat. For bothcrops the course of early leaf area expansion and ofS_LA withair temperature is not robust over environments and genotypes.The consequences of these results for modelling are discussed.Copyright 2000 Annals of Botany Company Triticum aestivum, spring wheat, winter wheat, Solanum tuberosum, leaf area expansion, specific leaf area, early growth, genotype, environment, modelling     

Inhibition of Gibberellic Acid-Induced Elongation-Growth of Pea Epicotyls by Xyloglucan Oligosaccharides

The biological activity of a cell wall-derived xyloglucan nonasaccharide(XG9) was investigated using a bioassay with entire pea epicotyls(Pisum sativum cv. Progress). The xyloglucan fragment was foundto inhibit gibberellic acid-induced elongation of etiolatedpea epicotyls with maximum inhibition at concentrations rangingfrom 10^–11 to 10^–9M. Growth of etiolated epicotylsin the absence of exogenously applied GA₃ was also inhibitedby XG9 in the same concentration range. A cell wall-derivedheptasaccharide (XG7) lacking the fucosyl-galactosyl-side chainshowed no inhibitory effect in the pea epicotyl bioassay withand without exogenous GA₃. Furthermore, the biological activityof a synthetic pentasaccharide (XG5), containing the fucosylgalactosyl-sidechain which is necessary for the biological activity was investigatedin the same bioassay. Compared to XG9 the pentasaccharide hada similar inhibitory activity on GA₃-promoted elongation aswell as on the endogenous growth in the absence of exogenouslyapplied GA₃, but did not exhibit a distinct concentration optimum. Key words: Elongation-growth, gibberellic acid (GA₃), oligosaccharides, pea, XG9     

Regulation of IBA synthetase from maize (Zea mays L.) by drought stress and ABA

The rate of indole-3-butyric acid (IBA) synthesis in maize seedlingsis dependent on the culture conditions of the plants. When theseedlings were grown on filter paper soaked with different amountsof water, the activity of IBA synthetase differed strongly.High amounts of water (150 and 200 ml per bowl) inhibited IBAsynthesis completely in vitro, whereas 30 and 50 ml water perbowl increased the activity dramatically. Under conditions whereIBA synthetase was inhibited (150 ml H₂O), an increase of enzymeactivity was observed when abscisic acid (ABA) was exogenouslyadded in concentrations between 510^–4 to 510^–7M. Under ‘drought’ conditions (50 ml H₂O per bowl)the same ABA concentrations were inhibitory. Jasmonic acid andsalicylic acid also enhanced IBA synthetase activity to someextent, whereas indole-3-acetic acid (IAA) and kinetin had noeffect. Activity could also be enhanced by osmotic stress (NaCIand sorbitol), but not under temperature stress. In accompanyinginvestigations the endogenous contents of IAA, IBA, and ABAunder the different culture conditions have been determinedas well as the energy charge of the seedlings. Similar observationshave been made with Amaranthus, wheat and pea seedlings Key words: Abscisic acid, Amaranthus paniculatus, drought stress, inole-3-butyric acid biosynthesis, Pisum sativum, Triticum aestivum, Zea mays     

Some Properties of an Acid Phosphatase Isolated from the Seed Coats of Developing Pea Seeds

An acid phosphatase (EC 3 1 3 2)isolated from the seed-coatsof developing pea seeds was estimated to have MW 30000 by gelfiltration on Sephadex G-75 It was shown to act on a broad spectrumof physiological substrates, the most preferred being ß-glycerophosphate,3-phosphoglycerate and ADP, wich all showed rates of about halfthe maximum rate shown with p-nitrophenyl phosphate (p-NPP)Another model substrate frequently used in enzyme localizationstudies, -naphthyl acid phosphate, was hydrolysed at about 30% of the rate shown with p-NPP This acid phosphatase was enhancedor stabilized by the chelators EDTA and 1, 10-phenanthrolme,unaffected by Mg²⁺ and N-ethyl maleimide, but strongly inhibitedby Zn²⁺ and F^– Both oxidized and reduced glutathione werewithout effect at low concentration and slightly inhibitoryat high concentration (15 mm) Thiol groups are clearly not involvedin regulating the activity of this acid phosphatase, a featurewhich distinguishes it from acid phosphatases from several otherplant species. Pisum sativum L, pea, acid phosphatase, seed-coats, seed development     

Internode Length in Pisum: Variation in Response to a Daylength Extension with Incandescent Light

Lines representing a range of internode length and floweringgenotypes in Pisum sativum L. were grown in 8 h of daylightfollowed by either 16 h of darkness or incandescent light. Thestem elongation response index (RI = length in 24 h ÷length in 8 h) was least in the very short internode nana types,which are grossly deficient in gibberellins (GAs), and the verylong internode slender types, which behave as if saturated withGAs. The common tall (genotype Le) and dwarf (le) types (lepartially blocks conversion of GA₂₀ to the active form, GA₁)were all markedly responsive but the peak RI (based on the mostresponsive internode) was less in tall lines (1.79 to 2.78)than in dwarf lines (2.32 to 5.01) and the peak RI tended tooccur about three to four internodes earlier in tall than indwarf lines. The cry⁸ mutation reduced the RI. (Duplicate lengthloci La and Cry are probably concerned with GA reception.) Amongle dwarf lines, genotype La cry⁸, was generally less responsivethan La Cry, La cry^c and la Cry. Data from crosses showed thaton either an le La or le la background cry⁸ segregates had alower RI than cry⁸ segregates. On an le la background, cry⁸plants were shorter than cry^c plants, cry⁸ was partially dominantto cry⁸ and segregation was clear only in long days. On an lela background, cry^c plants were shorter than cry^c plants, cry⁸was partially dominant to cry⁸ and segregation was clear inlong or short days. The very high peak RI (5.0) of the microcryptodwarfline, L57, appeared to result, in part, from a marked foreshorteningof internodes 4 to 10 in the 8 h regime. In the 24 h regimeL57 (lm) had a fairly similar growth pattern to normal (Lm)cryptodwarf types. The peak RI tended to occur at a lower internode in early thanlate flowering lines, especially among dwarf types, and genotypeswith a day neutral flowering habit (genotype sn or dne) wereless responsive than their photoperiodic counterparts (Sn Dne). White fluorescent light, given as a daylength extension, wasmuch less effective than incandescent light at stimulating stemelongation suggesting control through the phytochrome equilibrium(P_tr/P_total). Pisum sativum, garden pea, daylength extension, flowering, genotype, gibberellin, hormone receptor, incandescent light, internode length, phytochrome, stem elongation     

Ca2+ depolarizes adrenal cortical cells through selective inhibition of an ATP-activated K+ current

Bovine adrenalzona fasciculata cells (AZF) express a noninactivatingK⁺ current(I_AC) whoseinhibition by adrenocorticotropic hormone and ANG II may be coupled tomembrane depolarization andCa²⁺-dependentcortisol secretion. We studiedI_ACinhibition byCa²⁺ and theCa²⁺ionophore ionomycin in whole cell and single-channel patch-clamp recordings of AZF. In whole cell recordings with intracellular (pipette)Ca²⁺concentration([Ca²⁺]_i)buffered to 0.02 µM,I_AC reachedmaximum current density of 25.0 ± 5.1 pA/pF(n = 16); raising[Ca²⁺]_ito 2.0 µM reduced it 76%. In inside-out patches, elevated[Ca²⁺]_idramatically reducedI_AC channelactivity. Ionomycin inhibited I_AC by 88 ± 4% (n = 14) without altering rapidlyinactivating A-type K⁺ current.Inhibition of I_ACby ionomycin was unaltered by adding calmodulin inhibitory peptide tothe pipette or replacing ATP with its nonhydrolyzable analog5'-adenylylimidodiphosphate.I_AC inhibition byionomycin was associated with membrane depolarization. When[Ca²⁺]_iwas buffered to 0.02 µM with 2 and 11 mM1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), ionomycin inhibitedI_AC by 89.6 ± 3.5 and 25.6 ± 14.6% and depolarized the same AZF by 47 ± 8 and 8 ± 3 mV, respectively (n = 4). ANG II inhibitedI_AC significantlymore effectively when pipette BAPTA was reduced from 11 to 2 mM. Raising[Ca²⁺]_iinhibits I_ACthrough a mechanism not requiring calmodulin or protein kinases,suggesting direct interaction withI_AC channels. ANGII may inhibitI_AC anddepolarize AZF by activating parallel signaling pathways, one of whichuses Ca²⁺ asa mediator.

     

Differential Effects of Day and Night Temperature on Development to Flowering in Rice

There are conflicting reports with regard to difference in effectsof day temperature (T_D) and night temperatures (T_N) on plantdevelopment. The objective of this study is to determine whetherthere are different effects ofT_DandT_Non development from sowingto flowering in rice (Oryza sativaL.). Plants of 24 rice cultivars were grown in naturally-lightedgrowth chambers at five diurnally constant (22, 24, 26, 28 and32 °C) and four diurnally fluctuating temperatures (26 /22,30 /22, 22 /26 and 22 /30 °C forT_D/T_Nwith 12hd^-1each) witha constant photoperiod of 12hd^-1. The treatments were selectedto enable the separation of effects ofT_DandT_Non developmentrate (DR). The response of DR to constant temperatures was typically nonlinear.This nonlinearity could not explain the difference in floweringdates between fluctuating temperatures with the same mean dailyvalue but oppositeT_D/T_Ndifferences. Differential effects ofT_DandT_NonDR to flowering were detected in all but one cultivar. In mostcases,T_Dexerted a greater influence thanT_N, in contrast withmany previous reports based on the assumption of a linearitybetween DR and temperature. The data were further analysed bya nonlinear model which separated effects ofT_DandT_N. The estimatedvalue for the optimumT_Nwas generally 25 –29 °C, about2 –4 °C lower than the estimated optimumT_Din mostcultivars. The effects ofT_DandT_Non DR were found to be interactivein some cultivars. These results form a new basis for modellingflowering dates in rice. Oryza sativa; rice; flowering; development; day and night temperature; thermoperiodicity     

Photosynthetic Oxygen Production Facilitates Translocation of 11C-Labelled Photoassimilates from Tendrils and Leaflets of Pisum sativum L

The translocation profiles of ¹¹C-photoassimilates from eithertendrils or leaflets of the compound leaf of Pisum sativum weresimilar in shape, speed and susceptibility to blockage by chillingand heat girdling. When the feed leaf component was exposedto an anaerobic gas stream consisting of N₂ gas supplementedwith 40 Pa CO₂, the export of previously-fixed ¹¹C-photoassimilatesfrom both leaflets and tendrils continued in the light, butstopped in the dark. However, in the light, translocation of¹¹C-assimilates from the leaflet was rapidly blocked by a flowof pure N₂ (i.e. anoxia). Movement of ¹¹C-assimilates from theleaf of another C₃ plant, sunflower, was similar to that fromthe pea leaflet. In contrast to both laminar leaf components,export from the tendrils was stopped under pure N₂ only in thedark. Taken together the data suggest that photosynthetic O₂production facilitated the movement of ¹¹C-assimilates in theabsence of exogenous O₂. The differences observed between thetendrils and the leaflets exposed to pure N₂ could be attributedto the greater capacity of tendrils to produce and recycle CO₂to support photosynthetic O₂ production in the light. Key words: Pea, ¹¹C-translocation, anoxia, tendril, leaflet     

Maintenance and Growth Components of Carbon Dioxide Efflux from Growing Pea Fruits

Carbon dioxide efflux from 5- to 20-day-old pea fruits was measuredfor plants grown in controlled environment at 15 °C and600 µmol s^–1 m^–2 photon flux density in a16 h photoperiod. The rate of CO₂ output per fruit increasedquickly from 0.005 to 0.018 mg CO₂ min^–1 during fruitelongation and subsequently more slowly to 0.030 mg CO₂ min^–1as the fruits inflated. On a d. wt basis the rate was highest,0.175 mg CO₂ g^–1 min^–1, in the youngest fruits anddeclined curvilinearly with increasing fruit weight to 0.02mg CO₂ g^–1 min^–1. Separation of maintenance andgrowth components was achieved by starvation methods and bymultiple regression analysis. From the latter method estimatesof the maintenance coefficient declined hyperbolically from150±8.7 mg carbohydrate g^–1 d. wt day^–1 inthe very young fruits (0.05 g) to 10.4±0.36 mg carbohydrateg^–1 d. wt day^–1 in older fruits (2.0 g). On a nitrogenbasis maintenance costs decreased from 2240 to 310 mg carbohydrateg^–1 nitrogen day^–1 while nitrogen concentrationfell from 6.7 to 3 per cent d. wt. A simple linear relationshipbetween maintenance cost per unit d. wt and nitrogen concentrationwas not observed. A growth coefficient of 50±6.7 mg carbohydrate g^–1growth (equivalent to a conversion efficiency, Y_G, of 0.95)was estimated for all fruits examined. The overall efficiency, Y, increased from a mean of 0.70 to0.85 during fruit elongation and subsequently declined to 0.80.For a given fruit weight, efficiency increased asymptoticallywith relative growth rate; both asymptote and slope of the relationshipincreased as the fruits grew. Pisum sativum L., garden pea, legume fruit, carbon dioxide efflux, maintenance respiration, growth respiration