Structural and Histochemical Changes in Palisade Cells of Prosopis juliflora Seed Coat in Relation to its Water Permeability

Histochemical investigations on the Prosopis juliflora seedcoat indicate the occurrence of a hydrophobic ‘strip’as the primary water barrier. Its position and the structureand histochemistry of the palisade cells of the seed coat differaccording to their location on the seed. These differences maybe responsible for differences in the water permeability ofvarious parts of the seed coat. In particular, parts of theseed coat in which the hydrophobic ‘strip’ is locatedmore superficially tend to be more water impermeable than partslike the chalaza, in which the ‘strip’ is more deeplylocated within the palisade cells. Prosopis juliflora, seed coat impermeability, palisade cells, hydrophobic ‘strip’     

Changes in Levels of Naturally Occurring Gibberellin-like Substances during Germination of Seed of Lycopersicon esculentum Mill.

Naturally occurring gibberellin-like substances possessing acidic,basic, and neutral properties were detected, by paper partitionchromatography, in ethanolic extracts of tomato seed and ofetiolated seedlings after 72 and 116 hours' growth. Dwarf maizemutants of the d-1 and d-5 types, ‘Meteor’ pea seedlingsand young ‘Potentate’ tomato plants were used asbioassay material. Hydrolysis of seed and seedling proteinsby ficin in phosphate buffer, pH 6.2, after removal of ethanol-solublesubstances, liberated more and different ‘bound’gibberellin-like substances. It is suggested that protein hydrolysisduring germination is an important means of liberating thesesubstances at different stages of seedling development. Acidic substances were present in all the extracts prepared,but in general two with Rfs 0.25 and 0.55 in iso-propanol: ammonia:water : : 10:1:1 v/v were differentiated on d-2 and d-5 maizerespectively. Neutral substances in dry seed extracts chromatographedin the same solvent, had Rfs of 0.05, 0.35, and 0.95 and thesewere found only in the ethanolic (‘free’) extracts.They were active on d-1 and d-2 maize and ‘Meteor’pea. Basic gibberellin-like substances with Rfs of 0.05 and0.35 were found in ‘free’ extracts of both dry seedand etiolated seedlings after 116 hours' growth which were activeon d-2 maize only. Two others with Rfs 0.45 and 0.95 were extractedfrom seedlings after 72 hours' growth and these were activeon young ‘Potentate’ tomato plants. It is suggested that certain gibberellin-like substances, capableof reversing dwarfism in test plants, may be responsible formorphogenetic or other responses not involving stem extensionin the parent species. Changes were found in the levels of gibberellin-likesubstances but there was no evidence of changes in levels ofseed inhibitors relative to seed growth substances.     

Immunochemical Investigations with Highly Purified Glutamate Dehydrogenase from Pea Seeds by Means of the Ouchterlony Test

Monospecific antibodies have been prepared with a homogeneousprotein fraction of the main activity band of pea seed glutamatedehydrogenase. This protein precipitates with its antibodiesin a single band with complete fusion as seen by the Ouchterlonydouble-diffusion test. Identical behaviour is observed withthe protein of the adjacent activity bands of the multiple molecularforms of this enzyme and the antibodies to the former fraction.Organ-specific ‘isoenzymes’ of glutamate dehydrogenasewith preparations of pea roots and epicotyls are not detectedby this procedure. Partially purified glutamate dehydrogenasepreparations from Lemna perpusilla, Zea mays, and Oryza sativaalso precipitate with the antibodies to the pea protein. TheLemna protein is shown to be different from the pea enzyme asjudged from immunological behaviour. The pea antibodies¹ donot cross-react with glutamate dehydrogenases from Candida orbeef liver, nor do the beef liver antibodies react with thepea and Candida enzymes.     

Seed Coat Structure and Histochemistry of Abelmoschus esculentus. Chalazal Region and Water Entry

The seed coat structure and histochemistry of Abelmoschus esculentuswere studied by bright-field, fluorescence and scanning electronmicroscopy. The seed coat was typical of species of the Malvaceae.The endotesta cells had inner tangential walls which were verythick and autofluorescent. The occurrence of phenolic substancesat this level has been related to seed coat imposed dormancy.The palisade cells were composed of three differently shapedparts: an upper ‘prismatic part’, a medium ‘transitionpart’ and a lower ‘twisted part’. The formerwas rich in hydrophilic substances, the latter was lignified.The swelling of the ‘prismatic parts’ was relatedto seed coat cracks. The region controlling onset of water entrywas thought to be the chalazal area. Thanks to the presenceof a large amount of highly acidic polysaccharide, water wasable to penetrate from the permeable maternal tissue, throughthe chalazal cap and plug as far as the boundary between thepalisade and underlying mesophyll. During imbibition of watera kidney-shaped ‘blister’ was seen to rise, formedby separation of the palisade cells from an underlying singlelayer of subpalisade cells. The palisade layer forming the blisterroof showed the same histochemical characteristic of other seedregions. The single layer of the blister floor showed an affinitywith Toluidine Blue O and Alcian blue. Both blister roof andfloor were strongly autofluorescent. Abelmoschus esculentus (L.) Moench, okra, seed coat, chalazal region, water entry, structure, histochemistry     

Studies on Mature Seeds of Cuscuta pedicellata and C. campestris by Electron Microscopy

The seeds of Cuscuta pedicellata have been investigated by transmissionand scanning electron microscopy. Additional observations havebeen made on seeds of C. campestris by SEM only. The seed coatconsists of an outer single epidermis, two different palisadelayers, and an inner multiparenchyma layer. The outer epidermalwall in C. pedicellata has a thick cuticle and zones rich inpectic substances. The thicker ‘U-shaped’ cell wallsin the outer palisade layer are strengthened by a wall layerof hemicellulose. The inner palisade layer has thick walledcells with a ‘light line’. The inner cell wall ofthe compressed multiparenchyma layer has a thin cuticle. A fairlythick cuticle is positioned directly on the endosperm surface.The aleurone cell walls are different from the remaining endospermwalls. The latter are thick and believed to be of galactomannans.There is a ‘clear’ zone between the plasmalemmaand the cell wall in the aleurone cells. The embryo cells arepacked with lipids and proteins. In Cuscuta campestris mostendosperm has been absorbed during the seed development. Theembryo apex has two minute leaf primordia. The features of theCuscuta seeds are discussed in relation to functional and environmentalconditions. Cuscuta pedicellata, Cuscuta campestris, seed, seed coat, cuticle, cell walls, endosperm, aleurone cells, galactomannan, embryo, TEM, SEM     

The relationship between 'dehydrin-like' proteins and seed longevity in Ranunculus sceleratus L.

The relationship between the abundance of proteins homologousto the dehydrin/RAB group of LEAs and seed longevity has beenstudied in Ranunculus sceleratus L. The presence of these ‘dehydrin-like’proteins was not related to increases in seed longevity associatedwith seed development or priming treatments. Similarly, a drying-inducedincrease in the amount of ‘dehydrin-like’ proteinswas not accompanied by an improvement in longevity. Key words: Dehyclrin, LEA, longevity, R. sceleratus, seed     

Protein Synthesis During Rehydration, Germination and Seedling Growth of Naturally and Precociously Matured Soybean Seeds (Glycine max)

Soybean seeds [Glycine max (L.) Merr.] synthesize de novo andaccumulate several non-storage, soluble polypeptides duringnatural and precocious seed maturation. These polypeptides havepreviously been coined ‘maturation polypeptides’.The objective of this study was to determine the fate of maturationpolypeptides in naturally and precociously matured soybean seedsduring rehydration, germination, and seedling growth. Developingsoybean seeds harvested 35 d after flowering (mid-development)were precociously matured through controlled dehydration, whereasnaturally matured soybean seeds were harvested directly fromthe plant. Seeds were rehydrated with water for various timesbetween 5 and 120 h. Total soluble proteins and proteins radio-labelledin vivo were extracted from the cotyledons and embryonic axesof precociously and naturally matured and rehydrated seed tissuesand analyzed by one-dimensional PAGE and fluorography. The resultsindicated that three of the maturation polypeptides (21, 31and 128 kDa) that had accumulated in the maturing seeds (maturationpolypeptides) continued to be synthesized during early stagesof seed rehydration and germination (5–30 h after imbibition).However, the progression from seed germination into seedlinggrowth (between 30 and 72 h after imbibition) was marked bythe cessation of synthesis of the maturation polypeptides followedby the hydrolysis of storage polypeptides that had been synthesizedand accumulated during seed development. This implied a drasticredirection in seed metabolism for the precociously maturedseeds as these seeds, if not matured early, would have continuedto synthesize storage protein reserves. Glycine max (L.) Merr, soybean, cotyledons, maturation, germination/seedling growth     

Developmental control of xylem hydraulic resistances and vulnerability to embolism in Fraxinus excelsior L.: impacts on water relations

The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 10^–4M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar ‘Alaska’, an ABA-deficientmutant ‘wil’, and its ‘wildtype’. Freezinginjury was determined graphically as the temperature that caused50% injury (T₅₀) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T₅₀ for root tissuewas 1C for all genotypes, regardless of treatment. For ‘Alaska’shoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by –1.5 to –4.0C, while coldtreatment increased the freezing tolerance by –7.5 to–14.8C. Cold treatment increased the freezing toleranceof shoot tips by –9 and –15C for ‘wil’and ‘wild-type’, respectively. Cold acclimationincreased endogenous ABA concentrations in ‘Alaska’shoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of ‘Alaska’, respectively.In ‘Alaska’ shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in ‘wil’and ‘wild-type’ shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization     

Freezing tolerance, protein composition, and abscisic acid localization and content of pea epicotyl, shoot, and root tissue 3

The freezing tolerance of many plants, such as pea (Pisum sativum),is increased by exposure to low temperature or abscisic acidtreatment, although the physiological basis of this phenomenonis poorly understood. The freezing tolerance of pea shoot tips,root tips, and epicotyl tissue was tested after cold acclimationat 2C, dehydration/rehydration, applications of 10^–4M abscisic acid (ABA), and deacclimation at 25C. Tests wereconducted using the cultivar ‘Alaska’, an ABA-deficientmutant ‘wil’, and its ‘wildtype’. Freezinginjury was determined graphically as the temperature that caused50% injury (T₅₀) from electrical conductivity. Endogenous ABAwas measured using an indirect enzyme-linked immunosorbant assay,and novel proteins were detected using 2-dimensional polyacrylamidegel electrophoresis. The maximum decrease in T₅₀ for root tissuewas 1C for all genotypes, regardless of treatment. For ‘Alaska’shoot tips and epicotyl tissue, exogenous ABA increased thefreezing tolerance by –1.5 to –4.0C, while coldtreatment increased the freezing tolerance by –7.5 to–14.8C. Cold treatment increased the freezing toleranceof shoot tips by –9 and –15C for ‘wil’and ‘wild-type’, respectively. Cold acclimationincreased endogenous ABA concentrations in ‘Alaska’shoot tips and epicotyls 3- to 4-fold. Immunogold labeling increasednoticeably in the nucleus and cytoplasm of the epicotyl after7 d at 2C and was greatest after 30 d at the time of maximumfreezing tolerance and soluble ABA concentration. Cold treatmentinduced the production of seven, three, and two proteins inshoot, epicotyl, and root tissue of ‘Alaska’, respectively.In ‘Alaska’ shoot tissue, five out of seven novelproteins accumulated in response to both ABA and cold treatment.However, only a 24 kDa protein was produced in ‘wil’and ‘wild-type’ shoot and epicotyl tissues aftercold treatment. Abscisic acid and cold treatment additivelyincreased the freezing tolerance of pea epicotyl and shoot tissuesthrough apparently independent mechanisms that both resultedin the production of a 24 kDa protein. Key words: Pisum sativum, cold acclimation, immuno-localization     

Free Proline and Prolamin Protein in the Grain of Three Barley Varieties Subjected to a Gradient of Water Supply

Three barley varieties (Atem, Arabic Abiad and Beecher) weregrown on a line source sprinkler to establish a gradient ofwater supply from rain-fed (218 mm) to fully irrigated (330mm). Developing ‘seeds’ were analysed for free grainproline at three stages up to maturity. At the milk stage allthree varieties showed a strong inverse correlation (r>0–95)between free proline and irrigation treatment. A pronouncedinter-varietal difference was evident with the relatively drought-intolerantAtem having 213 nmol seed^–1 free proline when rain-fedas compared with Arabic Abiad or Beecher which had about 120nmol seed^–1 free proline at this stage. By maturity thiscorrelation was lost in all varieties, with most of the freeproline being incorporated into protein. Prolamin protein production was not impaired by drought in anyof the varieties, when measured on a per seed basis. There wassome indication that it may even rise in concentration in severelydrought-stressed plants. The results are discussed in relation to the decline in finalgrain yield with increased water deficit. Each of the threevarieties tested showed different yield responses along theirrigation gradient. These may reflect the physiological tolerancesto drought of each variety. At the milk stage the measurementof free ‘grain’ proline as a diagnostic for droughtstress tolerance may be of some value. Key words: Drought stress, seed physiology, proline     

'Callose' in the Impermeable Seed Coat of Sesbania punicea

Dry legumes of Sesbania punicea (Cav.) Benth. contain impermeableseeds which are either beige-greenish or reddish. When keptin water for over one year they do not swell. Quick imbibitionwas induced by a deep cut, abrasion with coarse abrasive paper,immersion in concentrated sulphuric acid, in boiling water andin boiling KOH solutions. Neither lipid solvents (acetone, chloroform,cyclohexane, diethyl ether, ethanol, xylene), nor, at room temperature,KOH solutions up to 50% per cent, permeabilized the seeds. Astrong barrier to water entry appeared to be located in thepalisade layer which showed ‘light points’ in places,and which seemed to be transversal thickenings. In the testa,‘ callose’, which may play a role in the impermeabilityof the Sesbania punicea seed, was detected. Sesbania punicea, germination, seed dormancy, seed coat impermeability, ‘callose’     

Sulphydryl and Disulphide Levels in Protein Fractions from Hydrated and Dry Leaves of Resurrection Plants

Significant changes in sulphydryl (‘SH’) and disulphide(‘SS’) levels during air-drying in leaves of ‘resurrection’plants (whose protoplasm survives dehydration) stemmed mainlyfrom protein turnover effects. No significant changes were foundin the SH, SS levels in leaves of the desiccation sensitivespecies Sporobolus pyramidalis following air-drying. The three tolerant species studied differed in the directionof change. Some data were consistent with Levitt's SH, SS hypothesis:increases in protein-SS levels in Sporobolus stapfianus (desiccationtolerant) were consistent with a stabilization of new proteinby SS bonds; lower reactivity of protein-SH in the tolerantspecies Talbotia elegans (which on the other hand has decreasedprotein-SS) is consistent with a second mechanism of decreasingprotein denaturation proposed in Levitt's hypothesis. Evidence of some conversion of SH to SS in the soluble proteinsof Xerophyta viscosa (a tolerant species) would on Levitt'shypothesis indicate an injurious process. Some degree of proteindenaturation might be indicated by partial inactivation of thesoluble enzyme ribulose bisphosphate carboxylase in this species,and loss of some soluble isoenzymes (peroxidase and alkalinephosphatase). An apparent lack of SH conversion to SS in thesensitive species Sporobolus pyramidalis was not consistentwith the SH, SS hypothesis. Resurrection plants, Sporobolus pyramidalis, Sporobolus stapfianus, Talbotia elegans, Xerophyta viscosa, drought resistance, desiccation tolerance, protein turnover, sulphydryl groups     

Changes during Development in the Nitrogen, Uncombined Amino Acid and Carbohydrate Contents of Cotyledons from Different Cultivars and Lines of Field Bean (Vicia faba L.)

A study has been made of the changes during development in thetotal nitrogen, uncombined amino acid, starch and ethanol-solublesugar contents of field bean cotyledons from two large-seededcultivars, Minica and Felix, and two lines of the small-seededcultivar Dacre, which differed in protein concentration of themature seed. In all cultivars the concentration of total nitrogen,uncombined amino acids and ethanol-soluble sugars decreasedwhile that of starch increased during development. However,the pattern of decrease in the proportion of total nitrogenvaried between the large and the small-seeded cultivars. Fromday 40 (after pollination) onwards a higher percentage of ethanol-solublesugars but a lower percentage of starch was found in the large-seededcultivars. Throughout development the Dacre line with the ‘high’protein concentration in the mature seed maintained a higherpercentage of total nitrogen and a correspondingly lower percentageof ethanol-soluble sugars and starch than the ‘low’protein line. Vicia faba L., field bean, nitrogen, starch, amino acids, sugars, protein     

A Seed Treatment for Eliminating Non-hybrid Plants when using Atrazine Resistance as a Genetic Marker for Hybrid Seed Production

Brassica plants, with a combination of chloroplasts encodingtriazine resistance and mitochondria encoding cytoplasmic malesterility, offer new opportunities for hybrid seed production.Such plants can be grown as a random mixture with a male parent,thereby allowing more effective pollen transfer for greaterefficiency of hybrid seed production. Harvested seed consistsof hybrid seed from the ‘female’ parent, which istriazine-resistant, and non-hybrid, triazine-sensitive seedresulting from self pollination of the ‘male’ parent. This study demonstrates that triazine-sensitive broccoli (BrassicaoleraceaL. var.italica) progeny can easily be eliminated byallowing the seed to imbibe a solution of 10 g l^-1atrazine overnightthen drying-back the seed for subsequent germination. Such atreatment prevents triazine-sensitive broccoli from developingbeyond the cotyledon stage following germination, and remainseffective for at least 3.5 years after seed treatment. The growthof triazine-resistant broccoli plants is unaffected by thisseed treatment. Atrazine; Brassica oleracea; broccoli; hybrid seed; triazine resistance; seed treatment     

Effects of Inorganic Phosphate on the Utilization of Sucrose by Suspension-cultured Catharanthus roseus Cells

The metabolic fate of [U-¹⁴C]sucrose in suspension culturesof Catharanthus roseus cells was monitored for 96 h after thecells were transferred to fresh complete (‘+Pi’)or to phosphate-deficient Murashige and Skoog (‘–Pi’)medium. Sucrose was hydrolysed extracellularly to glucose andfructose. The rate of uptake of sugars by the cells was 1.5–3times higher in ‘+Pi’ culture than in ‘–Pi’culture. Little difference in the rate of incorporation of radioactivityinto the ethanol-soluble fraction was found between the ‘+Pi’and ‘– Pi’ cultures during the initial 24h of culture, but after 48 h the rate in ‘ +Pi’cultures was higher than that in ‘–Pi’ cultures.Incorporation of radioactivity into ethanol-insoluble macromoleculeswas always significantly higher in the cells in ‘+Pi’cultures than in those in ‘–Pi’ cultures.The results suggest that Pi strongly affects the utilizationof sugars by cultured plant cells through the stimulation oftransport of sugars as well as through the activation of metabolism. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, sucrose, transport, metabolism     

The Growth and Carbon Economy of Selection Lines of Lolium perenne cv. S23 with Differing Rates of Dark Respiration: 2. Grown as Young Plants from Seed

Young plants of two selection lines of Lolium perenne cv. S23with ‘fast’ and ‘slow’ rates of ‘maturetissue’ respiration were individually grown from seed,together with plants of S23, their common parent, in 9.2 cmpots in a controlled environment at 20/15 °C day/night temperatures. No significant differences were found between the genotypesin leaf extension and tiller production during this early stageof their growth. They did differ however, by an average of 26%,in the rate of dark respiration of fully expanded leaf laminae.The use of a simple model demonstrated that such a differencein respiration could alone account for the different rates ofdry matter production shown by the selection lines when grownas young crops from seed. Possible penalties of ‘slow’respiration are also considered. Lolium perenne L., ryegrass, respiration, maintenance respiration, stimulated swards, leaf growth, tiller production, carbon economy     

Predator-prey interactions between Isochrysis galbana and Oxyrrhis marina. II. Release of non-protein amines and faeces during predation of Isochrysis

During the growth of Isochrysis galbana, several non-proteinamines may be detected in the growth medium. Of these, one (termed‘TTl’) accumulates in proportion to the numbersof cells present. The concentrations of ‘TTl’, andof another (termed ‘TA’), are 3–5 times higherin cultures in which Isochrysis is predated by Oxyrrhis marina.The lowest estimates of the concentration of extracellular ‘TTl’are an order of magnitude higher than those of any protein aminoacid. Of the protein amino acids, some like glycine are utilizedduring predation while others, like histidine, accumulate inthe medium Because of the unknown N-content and reactivity ofthe non-protein amines during HPLC, it is not possible to sayif these compounds (together with other components of dissolvedorganic N) form a significant proportion of the unaccountedfor N in the system after predatory activity. During predationin the absence of detectable free ammonium (when Isochrysismay be expected to be N-deprived), particles accumulate in themedium. Most of these are <2.5 µ.m in diameter andare suggested to be remains of digested prey. There is evidenceof a reassimilation of these particles by prey-deplete Oxyrrhis.     

Identification of a chemically induced point mutation mediating herbicide tolerance in annual medics (Medicago spp.)

Background and Aims: Sulfonylurea (SU) herbicides are used extensively in cereal–livestockfarming zones as effective and cheap herbicides with usefullevels of residual activity. These residues can persist beyondthe cropping year, severely affecting legumes in general, andannual medics in particular, resulting in reduced dry matterproduction, lower seed yields and decreased nitrogen fixation.A strand medic cultivar, Medicago littoralis ‘Angel’,has been developed via chemical mutagenesis with tolerance toSU soil residues. Identifying the molecular basis of the observedtolerance was the aim of this study. Methods: Two F₂ populations were generated from crosses between ‘Angel’and varieties of intolerant M. truncatula, the male-sterilemutant tap and the cultivar ‘Caliph’. Genetic mappingwith SSR (single sequence repeat) and gene-based markers allowedidentification of the trait-defining gene. Quantitative geneexpression studies showed the activity of the respective alleles. Key Results: Segregation ratios indicated the control of SU-herbicide toleranceby a single dominant gene. SU herbicides inhibit the biosynthesisof the branched-chain amino acids by targeting the acetolactatesynthase enzyme, allowing the choice of a mapping approach usingacetolactate synthase (ALS) gene homologues as candidates. SSR-markeranalysis suggested the ALS-gene homologue on chromosome 3 inM. truncatula. The ALS-gene sequences from ‘Angel’and intolerant genotypes were sequenced. In ‘Angel’,a single point mutation from C to T translating into an aminoacid change from proline to leucine was identified. The polymorphismwas used to develop a diagnostic marker for the tolerance trait.Expression of the mutant ALS allele was confirmed by quantitativeRT-PCR and showed no differences at various seedling stagesand treatments to the corresponding wild-type allele. Conclusions: The identification of the trait-defining gene and the developmentof a diagnostic marker enable efficient introgression of thiseconomically important trait in annual medic improvement programs.     

CORRECTIONS, VOLUME 29

Part 1, under the frontispiece portrait of Dr. N. B. Eales,the words ‘President 1948–1951’ should havebeen added. Page 103, line 49, for ‘Newton Collection’ read‘Norman Collection (Canon Norman)’. 185, line 37, for ‘capillaris’ read ‘capillacca’. 188, Table 1, for ‘bemoralis’. read ‘nemoralis’. 188, Table 2, for ‘Cochlicella acuta (Müll)? ventrosa(Fér.)’ read ‘Cochlicella ventrosa (Fér.)’. 191, line 24, for ‘araheo-’ read ‘archeo-’.     

Sunflower Seed Proteins: Characterization and Subunit Composition of the Globulin Fraction

Salt soluble proteins from sunflower (Helianthus annuus) seedswere fractionated by isoelectric precipitation and analysedby electrophoresis. Three molecular species were detected bygradient polyacrylamide gel electrophoresis of the globulinfraction. Multi-dimensional gel electrophoresis analysis indicatesthat all these species contained similar intermediary subunitsof 60 000, 54 000, 48 000 and 40000 molecular weight, the twoformer being predominant. As shown by ion-exchange chromatographyunder dissociating and reducing conditions, the intermediarysubunits are composed of disulphide linked pairs of large ‘acidic’and small ‘basic’ subunits. Heterogeneity in molecularweight of these subunits was shown by electrophoretic studies.These results suggest that a major reserve protein in sunflowerseeds is similar to ‘legumin’ of plants of the familyLeguminosae. Key words: Sunflower, Seed globulin, Globulin subunits