Allocation of Organ Biomass in Perfect and Imperfect Flowers

Perianth M_P, gynoecium M_G, and androecium M_A dry-weight biomass(in g) of 39 species of perfect flowers was measured. Thesedata were pooled with published data from an additional 51 speciesand used to determine size-dependent variations in (M_G and M_A)in terms of the hypothesis that the quotient of M_G and M_A exceeds1·0 for out-breeding (xenogamous) species and less than1·0 for in-breeding (autogamous) species. Ordinary leastsquare regression of the pooled data (n = 90) showed M_G = 0·118M^0·916_P (r² = 0·884) and M_A = 0·186 M^0·975_P(r² = 0·865), indicating that the biomass of the gynoeciumproportionally decrease as floral size increases. The exponentsof these regressions indicate that the ratio of gynoecial toandroecial biomass decreased with increasing floral size suchthat comparatively small flowers (M_P < 0·0021 g) hadM_G/M_A > 1·0 (predicted for 'out-breeders') while comparativelylarger flowers (M_P > 0·0021 g) had M_G /M_A < 1·0(predicted for 'in-breeders'). Thus, on average, the type ofbreeding system was a size-dependent phenomenon. To test whether the biomass of a floral organ-type is a legitimateindicator of gender reproductive effort, the biomass (in g)of stamen filaments M_m and anther sacs M_AS of 39 species wasdetermined. Least square regression of these data showed M_AS= 0·188 M^0·854_fil (r² = 0·967), indicatingthat species with larger stamen filaments, on the average, boreproportionally smaller anther sacs and thereby cautioning againstthe uncritical use of the allocation of biomass to floral organ-typeas a strict gauge of gender-function investment. To determine whether the loss of one gender-function resultsin proportional reallocation of biomass to the remaining gender-function,the size-dependency of androecial and gynoecial biomass wasdetermined for a total of 33 perfect and imperfect flowers ofCucumis melo. Regression of the data obtained from perfect flowersyielded M_A = 0·402 M^1·47_P (r² = 0·898)and M_G = 4·63 M^1·36_P (r² = 0·842). SinceM_G/M_A M^0·11_P , the biomass allocation to the gynoeciumrelative to the androecium decreased with increasing floralsize. This result was consistent with the broad interpecificcomparison based on 90 species with perfect flowers . Regressionof the data for imperfect flowers yielded M_A = 0·151M^1·02_P (r² = 0·675) and M_G = 4·68 M^1·47_P(r² = 0·996), indicating a near allometric relation forthe androecium and a strong positive anisometry for the gynoecium.Thus, for flowers of comparable size, a loss of female genderobtains a modest to significant again in androecial biomasswhereas the loss of male gender yields only a slight increasein gynoecial biomass. Collectively, the results of these studies indicate that biomassallocation patterns are size-dependent phenomena whose complexitieshave been largely ignored in the literature.Copyright 1993,1999 Academic Press Allometry, floral biomass, reproduction     

STUDIES ON HOMOSERINE DEHYDROGENASE IN PEA SEEDLINGS

Partially purified homoserine dehydrogenase was prepared frompea seedlings. The optimum pH for this enzyme is approximately 5.4. The K_mvaluesfor ASA and TPNH are 4.6xl0^–4Af and 7.7xl0^–5M, respectively.This enzyme can also utilize DPNH but less effectively thanTPNH. In contrast with yeast homoserine dehydrogenase whichis insensitive to — SH reagents, the pea enzyme is inhibitedalmost completely by 10^–4MPCMB and 10^–5MHgCl₂, theinhibition being removed by 10^–2M thioglycolate. Homoserinedehydrogenase was found not only in decotylized seedlings, butalso in cotyledons. The significance of this enzyme in homoserine biosynthesis ingerminating pea seeds has been discussed. (Received February 20, 1961; )     

Characterization of Storage Proteins in Daucus carota L.: Two Novel Proteins Display Zygotic Embryo Specificity

Although maturation-related proteins are well known in the endospermof albuminous seeds, an important question is whether the zygoticembryo possesses its own maturation proteins. We report on theisolation and partial characterization of storage proteins ofcarrot (Daucus carota L. var Nandor) dry achenes and isolatedzygotic embryos, using one- and two-dimensional electrophoresistechniques, HPLC and amino acid sequencing. The presence ofa series of abundant polypeptides showing charge heterogeneity,that are rapidly degraded upon germination, was revealed inthe endosperm. These proteins consisted of glycoproteins, themost abundant of which displayed a molecular mass (M_r) of 58,000,albumins of M_r 42,000 comprising at least one rß-1,3-glucanase,and two globulins of M_r 90,000 and 50,000–55,000 respectively,the second being an oligomer composed of three subunits of M_r13,000, 20,000 and 30,000. None of these storage proteins identifiedin the endosperm were detected in zygotic embryos. In contrast,two novel proteins were isolated from zygotic embryos, namelya globulin family of M_r 50,000 and pI 6.3–6.8, which wasnamed "daucin", and a late embry-ogenesis abundant (LEA) proteinfamily of M_r 25,000 and pI6.3–6.6, named "RAB25". Sincethe latter proteins are apparently absent of the endosperm,these results suggest that the maturation of carrot zygoticembryos requires its own specific set of storage and LEA proteins. (Received July 15, 1997; Accepted October 28, 1997)     

Relationship between Coleoptile Elongation and Alcoholic Fermentation in Rice Exposed to Anoxia. II. Cultivar Differences

The relationship between coleoptile elongation and survivalvs. alcoholic fermentation of rice under anoxia is examinedusing eight cultivars differing in submergence tolerance. Anoxiawas imposed on either 1 or 4 d aerated seeds either by N₂ flushingsubmerged tissues or by incubating tissues in stagnant deoxygenatedagar at 0·1% w/v; the latter simulated the stagnant conditionsof waterlogged soil. Two cultivars that were most tolerant tosubmergence also had the greatest tolerance to anoxia, whilea submergence intolerant cultivar was also intolerant to anoxia. Coleoptile growth under anoxia was related to rates of ethanolsynthesis (R_E), however differences between growth during anoxiaand survival after anoxia indicated that post-anoxic injurymay also be important in rice seeds exposed to anoxia. The correlationbetween coleoptile growth and R_E measured on a tissue basisusing intact seeds was r² = 0·67 among six varietiesover 0-3 d anoxia. This correlation improved to about r² = 0·85using R_E of (embryos plus coleoptiles) over 0-3 d, or coleoptilesat 3 d after anoxia. Coleoptile growth of individual seeds wasusually poorly correlated to R_E in these cultivars at 2-3 dafter anoxia. When coleoptiles of similar lengths were obtainedfrom different cultivars using 4 d aerated seeds, there weredifferences in R_E and coleoptile growth which were related tocoleoptile growth during 3 or 5 d anoxia, either on a tissue(r² = 0·85) or a fresh weight basis (r² = 0·70-0·97respectively). Results are discussed in relation to factorswhich may limit ethanol synthesis in rice exposed to anoxiaand the importance of growth to the survival of seeds and matureplants during submergence in the natural environment.Copyright1994, 1999 Academic Press Anoxia, ethanol, alcoholic fermentation, Oryza sativa L., rice, submergence     

Relationship between Coleoptile Elongation and Alcoholic Fermentation in Rice Exposed to Anoxia. I. Importance of Treatment Conditions and Different Tissues

The relationship between coleoptile elongation and alcoholicfermentation of rice under anoxia is examined using seeds either:(a) N₂ flushed during submergence, (b) incubated in stagnantdeoxygenated agar at 0·1% w/v to simulate the stagnantconditions of waterlogged soil, or (c) incubated in waterloggedsoil. Coleoptile elongation growth was greater for N₂ flushing> stagnant agar > soil; seed survival was also greatestin this order over 1-5 d. Ethanol concentrations in coleoptiles and intact seeds (cv.IR42) were approximately 300 and 100 mol m^-3 respectively whenseeds were grown 3 d in stagnant agar, however 92% of the ethanolin seeds diffused into the external medium when solutions weremixed for 5-10 s. Coleoptile growth under anoxia was relatedto rates of ethanol synthesis (R_E) in different treatments;there was greater coleoptile growth and R_E for seeds in N₂ flushedsolutions than in stagnant deoxygenated agar. Coleoptile growthof individual seeds was also related to the R_E of each seedat 2-3 d after anoxia (r² = 0·46). Analysis of different tissues was important in evaluating growthand metabolism of coleoptiles. Although the coleoptile onlyaccounted for 0·7% of seed dry weight at 3 d after anoxia,it contained 21% of the ethanol produced by rice seeds. Therewere also three-fold higher rates of R_E on a fresh weight basisin expanding tissues in the base of the coleoptile relativeto the elongated tissues at the apex. Results are discussedin terms of the importance of environmental conditions usedto impose anoxia, quantification of R_E in specific tissues andthe possibility that under stagnant conditions high ethanolconcentrations in tissues may limit R_E and coleoptile growth.Copyright1994, 1999 Academic Press Anoxia, ethanol, alcoholic fermentation, Oryza sativa L., rice, submergence     

Common Bean (Phaseolus vulgaris L.) Mutants Defective in Root Nodule Formation: II GENETIC ANALYSIS

Genetic analysis of crosses between two induced, ineffectivelynodulating mutants of common bean, NOD238 and NOD109, revealedthat their mutated nodulation phenotype is under the controlof the same locus in both mutants. The two mutants also resultedallelic for poor pod fertility, the other trait common to themutants. F₁ plants from crosses with their wild types nodulatedeffectively and had wild type pod fertility. Ineffective nodulationand poor pod fertility traits co-segregated in the F₂generationin which plants with the mutant nodulation and pod fertilityphenotypes represented 12.5% of the total population. Analysisin F₃confirmed that these plants were homozygous for both mutatedcharacters. The results indicated both mutant traits studiedare determined by a single recessive allele, named sym-2, whoseinheritance is negatively affected by its pleiotropic effecton pod fertility determining a deficit of ineffectively nodulatingcombinations. In an allelism test with the non-nodulating mutantof common bean NOD125 it was found that ineffective nodulationis controlled at a different locus and that the two loci arenot linked. Key words: Phaseolus valgaris, nitrogen fixation, nodulation mutants, genetics     

Der Einflu{beta} verschiedener Lichtqualitaten auf Chlorophyllgehalt und Wachstum von Gewebekulturen aus Crepis capillaris (L.) WALLR.

The influence of different light qualities on chlorophyll contentand growth of tissue cultures from Crepis capillaris (L.) WALLR. Tissue cultures from Crepis capillaris growing on media (M₁; M₂ ; M₂-E) formed chlorophyll and intact chloroplasts onlyin the short wave length region of the visible spectrum (350–550nm). In red light (600–700 nm) as well as in darknessthey lost their chlorophyll after 8–10 weeks. The growth of Crepis-cultures was strongly influenced by lightand the nitrogen of the medium. The highest increase in freshweight (425–485% increase in 3 weeks) was attained inred light or in darkness on M₂ by cultures which had lost theirchlorophyll completely. M₂ contains nitrates, ammonium saltsand amino acids. In contrast, the increase in fresh weight ofgreen cultures growing on M₂ in blue or white light was considerablylower (155–180% increase in 3 weeks). Omission of amino acids, (M₂-E), resulted in the reduction ofthe growth (increase of fresh weight in 3 weeks: 120%) of thechlorophyll-free cells growing in the dark. Green cultures behaveddifferently on M₂-E. In white light they attained an increasein fresh weight of 245%. This suggests that the growth promotingeffect of the amino acids can be replaced by light. Results with cultures growing on M₁, which contains neitherammonium salts nor amino acids, point in the same direction.Green cultures in white or blue light grew better (90–100%increase in fresh weight in 3 weeks) on this "deficient" mediumthan chlorophyll-free tissues in red light or in darkness (20–30%increase in fresh weight in 3 weeks). Some aspects of thesefindings which concern the effect of light on growth are discussed. (Received November 28, 1969; )     

Priming and accelerated ageing affect L-isoaspartyl methyltransferase activity in tomato (Lycopersicon esculentum Mill.) seed

Damage and degradation of cellular proteins is observed duringage-induced seed deterioration. L-Isoaspartyl protein methyltransferase(EC 2.1.1.77 [EC] ) is an enzyme hypothesized to play a role in limitingand repairing age-induced damage to proteins. Tomato (Lycopersiconesculentum Mill. ‘New Yorker’) seeds were assayedfor changes in L-isoaspartyl methyl-transferase activity duringaccelerated ageing and after osmotic priming. Accelerated ageingof seeds for 1–4 d at 45C and 100% relative humidityreduced germination from 94% to 71%, increased the mean timeof germination (MTG) from 2.4 to 5.8 d, and was accompaniedby a correlative decrease in L-isoaspartyl methyltransferaseactivity (r²=0.90). Aged and untreated seeds were primed for7 d at 20C in darkness using aerated solutions of 3% KNO₃ orpolyethylene glycol 8000 (PEG) with equivalent osmotic potential(–1.25 MPa). Priming with KNO₃ decreased the MTG, butdid not improve germination percentage for untreated seeds.Priming did not affect L-isoaspartyl methyltransferase activityin untreated seeds, but restored activity in aged seeds primedin KNO₃ to levels near that of untreated seeds. Priming withPEG did not effectively improve the MTG or increase L-isoaspartylmethyltransferase activity. During germination, L-isoaspartylmethyltransferase activity remained constant for 48 h post-imbibitionand then declined, suggesting that the enzyme was developmentallyregulated and inactivated or degraded as radicle emergence occurred. Key words: L-Isoaspartyl methyltransferase, protein repair, seed priming, accelerated ageing, Lycopersicon esculentum     

Ethylene, Nitrate and Nitrite Interactions in the Promotion of Dark Germination of Common Purslane Seeds

Ethylene (10 µ1^–1) caused about one-third of highlydark-dormant seeds of common purslane (Portulaca oleracea L.)to germinate in the dark. Attempts were made to increase germinationin the dark with nitrate and ethylene combinations. When applieddirectly to the seeds, KNO₃ did not stimulate germination andKNO₃ plus ethylene did not increase germination above that ofethylene alone. Pre-incubation of seeds in KNO₃ for 4 to 7 dbefore the ethylene applications significantly increased germination.The effects of the KNO₃ pre-incubation were additive at eachof four ethylene concentrations (0.1–100 µ11^–1).Potassium nitrate was effective only when ethylene followedthe KNO₃ pre-incubation period. Potassium nitrite stimulatedabout 25 per cent of the seeds to germinate without a pre-incubationperiod and without ethylene. Also, ethylene plus KNO₂ enhancedgermination above that achieved by either stimulus alone. Silvernitrate did not block the ethylene promotion of germination,but reversed the typical ethylene inhibition of seedling growthfollowing germination. The results support the views that nitrateexerted its effect via conversion to nitrite within the seedand that the rate of nitrate conversion may be a limiting factorin the dark germination of common purslane seeds. Ethylene mayfacilitate nitrite activity by increasing seed sensitivity tothe stimulus. Common purslane, Portulaca oleracea L., ethylene, nitrate, nitrite, germination, dormancy     

Chlorophyll Deficiency Caused by a Specific Blockage of the C5-Pathway in Seedlings of Virescent Mutant Rice

Temperature-sensitive mutants of rice, designated virescent(v₁, v₂ and v₃), develop chlorophyll-deficient leaves at a restrictivetemperature (20°C) but develop nearly normal green leavesat a permissive temperature (30°C). Analysis of the chlorophyllbiosynthetic pathway in the virescent mutants indicated thatthe chlorophyll deficiency at the restrictive temperature wasdue to specific blockage of the C₅-pathway. Northern analysissuggested that the chlorophyll deficiency in the virescent mutantswas caused by specific inhibition of the expression of chloroplasttRNA^Glu. (Received October 22, 1993; Accepted January 25, 1994)     

Identification and Characterization of the Seed Storage Proteins from Alfalfa (Medicago sativa)

The major seed storage proteins in alfalfa are medicagin (alegumin-like globulin), alfin (a vicilin-like globulin) anda family of Lower Molecular Weight albumins (LMW₁₃). These comprise30%, 10% and 20%, respectively, of the total extractable proteinfrom cotyledons of mature seeds. Alfin is a heterogeneous oligomericprotein (Mr 150 kD) composed of polypeptides ranging in sizefrom Mr 50 to 14 kD (₁,-₆; 50, 38, 32, 20, 16 and 14 kD, respectively).Medicagin is also a high molecular weight oligomeric protein,but requires high concentrations of salt for solubilization.It is comprised of a family of individually distinct subunits,each composed of an acidic polypeptide (A₁–A₉; Mr 49 to39 kD) linked via disulphide bond(s) to a basic polypeptide(B₁, B₂, B₃; Mr 24, 23 and 20 kD, respectively). This pairingis highly specific and two families are recognizable on thebasis of the B polypeptide (B₃ or B₁/B₂). Subunits (M_r 50–65kD) are assembled as trimers (8S) or larger oligomers (12S–15S)in mature seeds. The lower molecular weight albumins (LMW₁–₃)are acidic (pl<6), and consist of sets of disulphide-bondedpolypeptides (Mr 15 and 11 kD). Key words: Medicago sativa, seed storage proteins, alfin, medicagin     

Flax and weld: archaeobotanical records from Mutina (Emilia Romagna, Northern Italy), dated to the Imperial Age, first half 1st century a.d.

In the city centre of Modena (Emilia Romagna, Northern Italy) a noteworthy amount of carpological remains attributable to flax and weld came to light dated to the Imperial Age (first half 1st century a.d.). Flax remains, i.e. capsules and extremely small seeds, suggest the presence of either immature seeds and fruits of cultivated flax (Linum usitatissimum L.) or of a wild flax species (Linum bienne Mill.). The quantity of these remains along with the co-presence of seeds of Reseda luteola, an important dye plant, leads to the hypothesis of the cultivation of both flax and weld for textile manufacturing purposes, which are attested as important in the economy of the Roman period.     

Characterization of Prolamins from Meadow Grasses: Homology with those of Wheat, Barley and Rye

Prolamin fractions were extracted from seeds of five speciesof temperate meadow grasses. SDS-PAGE showed the presence ofpolypeptidcs with M_rs of 20–30000 in Phieum pratense andDactylis glomerata, and between 30000 and 65 000 in Lolium perenneand in two species of Festuca (F. rubra and F. arundinacea).The fractions had broadly similar amino acid compositions withhigh glutamate+glutamine (29 to 35 mol %) and phenylalaninc(8 to 10 mol %), but there was some variation in the contentsof prolinc (10 to 23 mol %) and several other amino acids includinglysine (0.3 to 1.9 mol %). Automated Edman degradation of twogel filtration fractions from L perenne and one fraction eachfrom the other four species showed single major N.terminal aminoacid sequences. These were homologous with each other, and withthe -typc prolamins of wheat, barley and rye. Key words: Prolamins, meadow grasses, SDS-PAGE     

Changes in Respiratory Potential of Dormant and Non-dormant Galium aparine L. (cleavers) Seeds during Dry Storage

Hilton, J. R. and Thomas, J. A. 1987. Changes in respiratorypotential of dormant and non-dormant Galium aparine L. (cleavers)seeds during dry storage.—J. exp. Bot. 38: 1484–1490. Pre-germinative rates of O₂ uptake of two collections of Galiumaparine L. seed were compared throughout a 9 month period ofdry storage at 4 °C, 23 °C and at ambient (frost-protected)temperatures. Uptake of O₂ by the dormant seeds was generallyhigher than that of the less dormant seeds except when freshly-harvested.Moreover, changes in the O₂ consumption of seeds stored at ambienttemperatures could be associated with periods of germinationand seedling emergence in the field. The results are discussedin relation to changes in respiratory metabolism during dormancybreakage.     

Maintenance Respiration and Carbon Balance of Plants at Low Levels of Sodium Chloride Salinity

The daily course of carbon influx and efflux was measured inyoung plants of Phaseolus vulgaris, Xanthium strumarium, Zeamays, and Atriplex halimus, exposed to low levels of salinity(NaCl) and varying daytime light intensities. Maintenance respiration(R_M) was calculated. In Phaseolus, Xanthium, and Atriplex, R_Mrose with increasing salinity, approximately up to those levelsof salinity above which apparent signs of toxicity appear. Athigher levels of salinity R_M declined. There was no responseof R_M to salinity in Zea. At the levels of salinity tested,salinity did not affect the ratio of growth respiration to photosynthesis. At –5 x 10⁵ Pa of NaCl salinity, the increase in R_M inXanthium was calculated to account for 24% of the growth reductioncaused by salt. The remainder could be ascribed to reduced photosynthesis.The increase of R_M is considered to be indicative of an adaptivemechanism, not present in the very salt-sensitive Zea.     

Effects of Gibberellins on Seed Germination of Phytochrome-Deficient Mutants of Arabidopsis thaliana

Experiments were carried out to explore the involvement of gibberellins(GAs) in the light-induced germination of Arabidopsis thaliana(L.) Heynh, using wild type (WT) and phytochrome-deficient mutants(phyA, phyB and phyAphyB deficient in phytochrome A, B and Aplus B, respectively). Seed germination of WT and phytochrome-deficientmutants was inhibited by uniconazole (an inhibitor of an earlystep in biosynthesis of GA, the oxidation of ent-kaurene) andprohexadione (an inhibitor of late steps, namely, 2rß-and 3rß-hydroxylation). This inhibition was overcomeby simultaneous application of 10^-5 M GA₄. The relative activityof GAs for promoting germination of uniconazole-treated seedswas GA₄>GA₁=GA₉>GA₂₀. The wild type and the phyA and phyBmutants had an increased response to a red light pulse in thepresence of GA₁, GA₄, GA₉, GA₂₀ and GA₂₄ but there were no significantdifferences in activity of each GA between the mutants. Therefore,neither phytochrome A nor hytochrome B appears to regulate GAbiosynthesis from GA₁₂ to GA₄ during seed germination, sincethe conversion of GA₁₂ to GA₉ is regulated by one enzyme (GA20-oxidase). However, GA responsiveness appears to be regulatedby phytochromes other than phytochromes A and B, since the phyAphyBdouble mutant retains the photoreversible increased responseto GAs after a red light pulse. (Received February 13, 1995; Accepted July 11, 1995)     

Identification, Purification and Properties of the Precursor of Conglutin {beta}, The 7S Storage Globulin of Lupinus albus L. Seeds

Lupinus albus L. developing cotyledons 35 d after floweringcontained a major polypeptide of-average M_r 64000, immunologicallyrelated to conglutin ß, the 7S storage globulin ofthis seed. This polypeptide decreased during seed maturation,without completely disappearing in the mature seed. This dropwas accompanied by the formation of polypeptide fragments typicalof the mature conglutin ß. The 64000 polypeptide hasbeen identified as the precursor polypeptide of conglutin ß. Undenatured conglutin ß precursor, purified by ionexchange chromatography and size exclusion chromatography, showedsurface and association properties identical to the mature conglutinß molecule. The precursor oligomer, of M_r 190000,consisted of an association of three 64000 subunits. They stronglyreacted with concanavalin A indicating the presence of covalentlylinked carbohydrate. Tryptic treatment of the undenatured conglutin ß precursorled to the accumulation of a relatively stable 59000 polypeptidewhich was cleaved later on and produced three large polypeptidefragments differing from the mature conglutin ß polypeptides. Key words: Conglutin ß, precursor, developing seeds, Lupinus albus L.     

Inter-population Variations of Kochia indica During Germination Under Different Stresses

Germination of three populations of Kochia indica Wight fromcontrasting soil types were studied under various levels ofsalinity, alkalinity and osmotic stress with a view to evaluatetheir potential to establish through seeds in saline and alkalineenvironments of various magnitudes. The seeds were germinatedunder controlled conditions in Petri dishes using salinizedsolutions of NaCl, Na₂SO₄, MgCI₂ and CaSO₄ (electrical conductivity,EC, 4–16 ds m^–), sodium carbonate solutions (pH8.5–100), mannitol solutions ( – 2.5 to –100 bar) and de-ionised distilled water (control). Inter-populationdifferences were very marked, showing selective adaptation ofthe populations to a particular stress type. In general, allpopulations exhibited salt tolerance but were rather sensitiveto high osmotic stress. Kochia indica Wight (bui), germination, population, salinity, alkalinity, osmotic stress     

Limitations to net photosynthesis as affected by nitrogen status in jack pine (Pinus banksiana Lamb.) seedlings

Relative limitations of nitrogen (N) status on the processescontributing to photosynthetic rate (A) were investigated. Jackpine {Pinus banksiana Lamb.) seedlings from seeds grown in sandculture were supplied with four different N treatments for 6weeks, which resulted in a needle N content ranging from 50–85mmol m^–2 (14–32 mg g^–1 dry weight). Leaf gasexchange at varying CO₂ levels was measured and limitationson A₃₅₀ (A at ambient CO₂ level) caused by finite, limitingcarboxylation efficiency (c.e.), maximum A (A_max)and stomatalconductance were estimated from an analysis of the responseof A to internal CO₂ concentration. Although c.e. and A_max decreasedlinearly with the decline in needle N, the magnitudes of theirchanges relative to A₃₅₀ differed. A_max varied with A₃₅₀ andalways exceeded A₃₅₀ by 37–38% c.e., however, declinedfaster than A₃₅₀, as needle N level decreased. Consequently,relative limitation on A₃₅₀ caused by inefficient A_max remainedconstant, but limitations caused by c.e. increased by 10–15%at low N levels. In contrast, the limitation by stomatal conductancedeclined initially, but remained stable when N content droppedbelow 75 mmol m^–2. The results suggest: (1) a decreasein biochemical capacity, but not stomatal conductance, contributedto the reduction of A₃₅₀ induced by N-deficiency in jack pineseedlings; and (2) the capacity of carboxylation appeared tobe impaired more than that of electron transport and/or photophosphorylationand its reduction may be the major reason for the reductionin A₃₅₀. Key words: A–C_i analysis, carboxylation efficiency, electron transport, nitrogen deficiency, stomatal conductance     

Proteomic analysis of pathogenesis-related proteins (PRs) induced by compatible and incompatible interactions of pepper mild mottle virus (PMMoV) in Capsicum chinense L3 plants

Resistance conferred by the L³ gene is active against most ofthe tobamoviruses, including the Spanish strain (PMMoV-S), aP_1,2 pathotype, but not against certain strains of pepper mildmottle virus (PMMoV), termed P_1,2,3 pathotype, such as the Italianstrain (PMMoV-I). Both viruses are nearly identical at theirnucleotide sequence level (98%) and were used to challenge Capsicumchinense PI159236 plants harbouring the L³ gene in order tocarry out a comparative proteomic analysis of PR proteins inducedin this host in response to infection by either PMMoV-S or PMMoV-I.PMMoV-S induces a hypersensitive reaction (HR) in C. chinensePI159236 plant leaves with the formation of necrotic local lesionsand restriction of the virus at the primary infection sites.In this paper, C. chinense PR protein isoforms belonging tothe PR-1, β-1,3-glucanases (PR-2), chitinases (PR-3), osmotin-likeprotein (PR-5), peroxidases (PR-9), germin-like protein (PR-16),and PRp27 (PR-17) have been identified. Three of these PR proteinisoforms were specifically induced during PMMoV-S-activationof C. chinense L³ gene-mediated resistance: an acidic β-1,3-glucanaseisoform (PR-2) (M_r 44.6; pI 5.1), an osmotin-like protein (PR-5)(M_r 26.8; pI 7.5), and a basic PR-1 protein isoform (M_r 18;pI 9.4–10.0). In addition, evidence is presented for adifferential accumulation of C. chinense PR proteins and mRNAsin the compatible (PMMoV-I)–C. chinense and incompatible(PMMoV-S)–C. chinense interactions for proteins belongingto all PR proteins detected. Except for an acidic chitinase(PR-3) (M_r 30.2; pI 5.0), an earlier and higher accumulationof PR proteins and mRNAs was detected in plants associated withHR induction. Furthermore, the accumulation rates of PR proteinsand mRNA did not correlate with maximal accumulation levelsof viral RNA, thus indicating that PR protein expression mayreflect the physiological status of the plant. Key words: Capsicum chinense, compatible interaction, incompatible interaction, HR-induction, PMMoV, PR proteins Received 5 December 2007; Revised 21 January 2008 Accepted 22 January 2008