Exogenous Polyamines Stimulate Ethylene Synthesis by Soybean Leaf Tissues

Exogenous supply of spermine (Spm) markedly stimulated ethyleneevolution from intact soybean leaves of leaf discs, stronglyincreased the level of free 1-aminocyclopropane-1-carboxylicacid (ACC), and slightly stimulated ethylene forming-enzyme(EFE) activity Spm treatment also resulted in leaf epinastyand accelerated leaf senescence Ethylene stimulation was depressed,but not abolished, by light, and was suppressed by inhibitorsof ACC synthase and EFE activity Spermidine had a less pronouncedstimulatory effect on ethylene production whereas the diaminesputrescine and diaminopropane were without effect These resultscontrast with other reports indicating that di- and polyaminesinhibit ethylene biosynthesis in plants, and extend our previousresults on detached tobacco leaves exogenously treated withpolyamines Glycine max, ethylene, polyamines     

Growth Analysis of Soybean Seedlings During the Lifespan of the Cotyledons

Patterns of seedling growth of Glycine max in light and darknesswere compared during the period from germination to cotyledonabscission. Fitted growth curves and the derived functions,relative growth rate, unit leaf rate, leaf area ratio and specificleaf area, were used to assess the relative importance in seedlinggrowth of cotyledon storage reserves, cotyledon photosynthesisand leaf photosynthesis. The cotyledons are of an intermediatetype with a predominant storage and a minimal photosyntheticfunction. Cotyledon reserves support seedling growth until theprimary leaves expand, after which growth depends on leaf photosynthesis. Glycine max (L.) Merr., soybean, cotyledons, growth analysis, seedling development     

The Role of 1-Aminocyclopropane-1-carboxylic acid in the Control of Low Temperature Induced Ethylene Production in Leaf Tissue of Phaseolus vulgaris L .

Ethylene production from leaf discs of dwarf bean (Phaseolausvulgaris L.) was less than 02 nl g^–1 h^–1 at 5 Cbut rapidly increased tenfold on transfer to 25 C. The lowethylene production at 5 C and the potential for overshootproduction on transfer to 25C were not associated with accumulationof the ethylene synthesis intermediate 1-aminocyclopropane-1-carboxylicacid (ACC). Addition of exogenous ACC to leaf discs incubatedat 5C increased ethylene production, while similarly incubatedleaf discs did not synthesize increasing amounts of endogenousACC until they were transferred to 25 C. The basis for theovershoot in ethylene production when leafdiscs were transferredfrom 5 to 25 C appears to reside in changes to the pathwayleading to the synthesis of ACC or an earlier intermediate inthe pathway of ethylene biosynthesis. Ethylene, 1-aminocyclopropane-l-carboxylic acid, Phuseolru vulgaris L., dwarf bean, temperature     

Morphological Description of Transgenic Soybean Chimeras Created by the Delivery, Integration and Expression of Foreign DNA Using Electric Discharge Particle Acceleration

Transgenic soybean (Glycine max L.) plants derived from electricdischarge particle acceleration experiments exhibited varyingdegrees of chimerism which was followed by the expression ofthe introduced ß-glucuronidase (gus) gene. Degreesof chimerism in transgenic plants were established by determiningexpression of the gus gene observed as blue spots, streaks orsectors in stem and leaf tissues in in vitro grown plantletsand greenhouse plants. Clonal plants were also obtained. Presenceof the gene was confirmed by Southern blot analysis. These studiespermitted the reconstruction of a partial picture for the developmentof the soybean plant. Glycine max L. cv. Williams 82, soybean, transformation, ß-glucuronidase, chimeric plant phenotypes, development     

Effect of light on ethylene production and hypocotyl growth of soybean seedlings

The apical 1-cm hypocotyl of dark-grown `Clark' soybean (Glycine max [L.] Merr.) seedlings produced ethylene at rates of 7 to 11 nanoliters per hour per gram when attached to the cotyledons. Such physiologically active rates occurred prior to the deceleration of hypocotyl elongation caused by the temperature of 25 C.

Daily exposure of the etiolated seedlings to red light promoted hypocotyl elongation and prevented its lateral swelling. Red light treatment also caused a 45% decrease in ethylene production. Far red irradiation following the red treatment reversed the red effects, suggesting that the ethylene intervenes as a regulator in the phytochrome control of `Clark' soybean hypocotyl growth at 25 C.

     

Soyabean Stem In Vivo Nitrate Reductase Activity

Stem from three- and four-week-old Soyabean [Glycine max (L.)Merr. cv. Tracy] plants reduced from 0.3 to 0.7 µmol nitrateh^–l g^–l f. wt. Leaf activity was 4.7–7.6 µmolnitrate h^–l g^–l f. wt. Outer stem was two to fourtimes more active at reducing nitrate than was inner stem. Plantnitrate nutrition had a strong effect upon the ratio of activitypresent in stem and leaf. More nitrate increased the proportionpresent in leaves. Glycine max L., soyabean, nitrate assimilation, nitrogen metabolism, Rhizobium japonicum     

Assumptions of Plastochron Index: Evaluation With Soya Bean Under Field Drought Conditions

Erickson and Michelini (1957) derived the plastochron index(PI) and a term sometimes referred to as the plastochron ratio(PR), as quantitative expressions of the vegetative developmentof plants. With the stable plant growth in environmental chambersand glasshouses, the assumptions used to derive these termshave been validated. However, more recently these expressionsare being used to characterize growth under the unstable conditionsresulting from the imposition of stress. This study examinesthe validity of the assumptions used to derive PI and PR forfield-grown soya beans [Glycine max (L.) Merrill] subjectedto drought stress. Under stress conditions, the assumptionswere not satisfied. In fact, observing change in PR appearedto be a good method for detecting drought stress in these plants.An alternate method for calculating PI based on a single, youngleaf was developed. This alternate method appeared to be a moresensitive indicator of changes in leaf emergence rate underunstable conditions. Plastochron index, plastochron ratio, Glycine max (L.), soya bean, drought, leaf growth     

Changes in Soybean Raceme and Petiole Anatomy Induced by 6-Benzylaminopurine

An enlargement of the peduncle and rachis of the terminal racemeand the petiole of the uppermost mainstem leaf was observedin soybean plants [Glycine max (L.) Merr.] treated with thecytokinin, 6-benzylaminopurine (BAP). Histological studies wereperformed to determine the timing and extent of anatomical changesaccompanying BAP treatment. Swelling of treated ‘Tracy-M’peduncles, rachises, and petioles was observed within 4–6d after treatment initiation. A significant increase in totalcross-sectional tissue area was observed at lower and intermediateinternodes of treated rachises after 11 d. Rachis enlargementwas due to increases in both cell size and cell number, particularlyof the vascular tissue. In treated petioles of IX93-100, procambialcells of vascular bundles were the first to respond to the BAPtreatment. These cells differentiated into a vascular cambiumwhich formed secondary xylem and phloem. Soybean, Glycine max (L.) Merr., anatomy, rachis, BAP.     

Germination and Early Growth of Plants Studied Using Neutron Radiography

Seed swelling, germination, root extension, lateral root initiationand shoot growth were studied in soils of different water contents,using non-destructive, serial neutron radiography. Seeds fromthree varieties of soya beans (Glycine max L.) and one varietyeach of maize (Zea mays L.) and vetch (Vicia sativa L.) wereused. The seeds germinated when they had increased in size bya certain amount, if germination is taken as the time when theradicle first appears. The rate at which roots and shoots extendalso depend on soil water content. Glycine max L., Vicia sativa L., Zea mays L., Soya bean vetch, maize, seed germination, root extension, lateral root initiation, neutron radiography     

Effects of Free Radical Scavengers on Stress Ethylene in Soybean Leaves Hypersensitively Reacting to Tobacco Necrosis Virus

The hypersensitive reaction of soybean cuttings to tobacco necrosisvirus is characterized by a large stimulation of stress ethyleneinvolving a marked accumulation of free 1-aminocyclopropane-1-carboxylicacid (ACC) and a moderate increase in ethylene-forming enzyme(EFE) activity. The scavengers of hydroxyl radicals (OH^{dot})sodium benzoate, sodium formate, mannitol and dimethylsulphoxide,did not affect stress ethylene biosynthesis. Propyl gallate,an inhibitor of lipoxygenase enzymes, substantially reducedthe release of stress ethylene from hypersensitive leaves. Thisreduction was not attributable to an inhibitory effect on EFEactivity, but to a strong reduction of free ACC accumulationin leaf tissues. The results suggest that OH^{dot} and the lipoxygenasesystem are not involved in stress ethylene produced during thehypersensitive reaction of soybean to this virus. Glycine max Merr, soybean, ethylene, free radicals, hypersensitivity, tobacco necrosis virus     

Glutamine Synthetase Activity and Foliar Nitrogen Volatilization in Response to Temperature and Inhibitor Chemicals

In soyabeans (Glycine max (L.) Merr.), glutamine synthetase(GS) activity was greater at 28 °C than at 35 °C. Thereverse was true for foliar-N loss. In field-grown plants at29 °C, the GS activity was higher and foliar-N loss waslower in soyabeans than in Amaranthus palmeri (S.) Wats. Methioninesulphoximine, a GS inhibitor, and 6-diazo-5-oxo-L-norleucine,a glutamate synthase inhibitor, significantly increased foliar-Nloss from soyabeans. The data suggest that conditions conduciveto decreased GS or glutamate synthase activity may result inincreased foliar-N loss. Palmer amaranth, Amaranthus palmeri, soyabean, Glycine max, methionine sulphoximine, 6-diazo-5-oxo-L-norleucine     

Absence of red-light enhancement of phototropism in pea seedlings at limiting irradiances of blue light

The effect of different light qualities (blue, green, white, red and far-red) on ethylene production in leaf discs and flower petal discs of Begonia × hiemalis cv. Schwabenland Red was studied. All the light qualities, except far-red, reduced the ACC-conversion to ethylene in leaf discs by about 70% at a photosynthetic photon flux density (PPFD) of 20 mol m^–2s^–1.Blue and green light were less inhibitory than white and red light at lower PPFD. In all treatments far-red light at 0.5 mol m^–2s^–1 of photon flux density (PFD) stimulated the ACC-conversion to ethylene in leaf discs by about 60–90% compared to the dark-incubated control. White and red light strongly inhibited the -naphthalene-acetic acid (NAA) stimulated ethylene synthesis in leaf discs. The results may suggest that the ethylene production is controlled by phytochrome in the leaves but not in the petals. Lack of coaction of any light quality with silver ions on ethylene production in leaf and petal discs was also observed.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - EFE ethylene forming enzyme - NAA -naphthalene-acetic acid - PFD photon flux density - PPFD photosynthetic photon flux density - RH relative air humidity - SAM S-adenosylmethionine - STS silver thiosulphate     

Temperature and Seed Storage Longevity

Seed survival data for eight diverse species, namely the cerealbarley (Hordeum vulgare L.), the grain legumes chickpea (Cicerarietinum L.), cowpea [Vigna unguiculata (L.) Walp.] and soyabean [Glycine max (L.) Merr.], the timber trees elm (Ulmus carpinifoliaGleditsch.), mahogany (Swietenia humilis Zucc.), and terb (Terminaliabrassii Exell.), and the leaf vegetable lettuce (Lactuca sativaL.) were compared over a wide range of storage environments(temperatures from –13 °C to 90 °C, seed moisturecontents from 1.8 to 25% f. wt) using a viability equation developedpreviously. In accordance with that equation, the effect oftemperature on seed longevity was dependent upon the temperaturerange. The temperature coefficients of the viability equationdid not differ significantly (P > 0.05) among the eight speciesdespite their contrasting taxonomy. Thus the quantitative relationbetween seed longevity and temperature does not vary among diversespecies. The same conclusion was obtained for the coefficientsof a proposed alternative model of the relation between seedlongevity and temperature. The implications of the two temperaturemodels in the viability equation for extrapolations to low andvery low temperatures are discussed. Seed storage, seed longevity, seed moisture, temperature, viability equation, genetic resources conservation, Cicer arietinum L., Glycine max (L.) Merr., Hordeum vulgare L., Lactuca sativa L., Swietenia humilis Zucc., Terminalia brassii Exell., Ulmus carpinifolia Gleditsch., Vigna unguiculata (L.) Walp     

Acclimation of Photosynthate Partitioning and Photosynthetic Rates to Changes in Length of the Daily Photosynthetic Period

Pangola, soya bean and spinach plants were grown in long andshort day photosynthetic periods. Reciprocal shifts betweenlong and short day grown plants were made to study acclimationin the rate of leaf starch synthesis with change in daylength.The rate of leaf starch accumulation is a function of the lengthof the daily photosynthetic period. Acclimation, that is a changein partitioning with a change in length of the photosyntheticperiod, occurs in a variety of species. Acclimation in the rateof starch accumulation occurs rapidly in pangola and is apparentlycomplete the day after a change in length of the daily photosyntheticperiod. Soya bean and spinach leaves require a few days in thenew environment for an acclimation to occur. Digitaria decumbens Stent., Glycine max (L.) Merr., Spinacia oleracea L., pangola, soya bean, spinach, specific leaf weight, starch, photosynthesis     

Characters of Pod Anatomy Associated with Resistance to Pod-Shattering in Soybean

Seven characteristics of pod anatomy were studied for theirassociation with resistance to pod-shattering in 16 soybean[Glycine max (L.) Merrill] varieties and strains. The thicknessand length of the bundle cap on the dorsal side of the pod andpod-wall thickness were found to be significantly negativelycorrelated with the degree of pod-shattering. Further statisticalanalyses confirmed that these three anatomical characters werealmost equally important and could potentially serve as criteriafor the selection of resistance to pod-shattering. The identifiedtraits/sites in the pod represent sclerenchymous structuresand may provide the structural basis of resistance to pod-shatteringin soybean.Copyright 1995, 1999 Academic Press Pod, anatomy, shattering, soybean, Glycine max (L.) Merrill     

Ethylene formation in sugar beet leaves: evidence for the involvement of 3-hydroxytyramine and phenoloxidase after wounding

Ethylene production by sugar beet (Beta vulgaris L.) leaf discs is inhibited by white (or red, >610 nm) light or by wounding. In contrast, in wounded leaf discs, ethylene production is stimulated by light. The effect of light on wounded leaf discs has been studied by using an in vitro system which mimics the loss of compartmentation in the wounded leaf. Chlorophyll-free extracts from sugar beet leaves stimulate the production of the superoxide free radical ion (as a prerequisite for ethylene formation) by illuminated chloroplast lamellae. The substance from the crude leaf extracts which is active in stimulating the production of the superoxide free radical ion has been identified as 3-hydroxytyramine (dopamine). Exogenous dopamine between 5 mum and 100 mum stimulates ethylene formation by illuminated chloroplast lamellae from methional. It also stimulates the production of the superoxide free radical ion, the formation of which apparently involves both a lamellar phenoloxidase and photosynthetic electron transport as a 1-electron donor, and is cyanide-sensitive.     

Ethylene Release from Leaves of Xanthium strumarium L. and Zea mays L.

The release of ethylene into sealed Erlenmeyer flasks by intactleaves and leaf discs of Xanthium strumarium L. a C₃ plant andZea mays L. a C₄ plant were compared both in white light andin darkness. The effects of the presence or absence of addedCO₂ (in the form of sodium bicarbonate) the photosynthetic inhibitor3-[3,4-dichlorophenyl]-l, l-dimethyl urea (DCMU) and 1-aminocyclopropane-1-carboxylicacid (ACC), the precursor of ethylene in higher plants, werealso investigated. The rate of ethylene release from leaf tissue of Xanthium inthe absence of added CO₂ was markedly reduced in the light (i.e.at the CO₂ compensation point). Treatments that would enhancethe CO₂ availability to the tissue (i.e. added bicarbonate,darkness, treatment with DCMU) allowed higher levels of ethylenerelease. Incubation of the tissue with ACC considerably enhancedthe release of ethylene compared to that from the correspondingcontrol tissue without ACC. However, the pattern of ethylenerelease induced by the various treatments was similar with orwithout added ACC. When tissue, in the absence of added CO₂, was transferred fromlight to darkness, and back to light for 90 min periods, theethylene release rates Increased during the interposed darkperiod but resumed the lower rate during the final light period.The addition of CO₂ in the light resulted in a similar rateof ethylene release to that found in the dark. The overall pattern of ethylene release from Zea leaf tissuesubjected to light and dark in the presence or absence of addedCO₂ was similar to that of Xanthium. However, two or three timesmore ethylene was released from maize leaves in the light whenCO² was added compared to that generated in the dark. This isin marked contrast to Xanthium, where, under the light conditionsused, the ethylene release rate in the dark equalled or exceededthat occurring in the light, even in the presence of high levelsof CO₂. A very low rate of ethylene release was observed atthe CO₂ compensation point of maize. A speculative model is presented to explain how photosyntheticactivity might act as a key factor in regulating ethylene evolutionfrom leaf tissue in these experiments. It invokes the conceptof an inhibition by CO₂ of ethylene retention or breakdown thuspermitting more ethylene to be released from the leaves.     

The Effect of Light Intensity on the Release of Ethylene from Leaves

When leaf discs of Xanthium strumarium L. a C₃ plant, or Zeamays L. a C₄ plant, are incubated in 1-aminocyclopropane-l-carboxylicacid (ACC) in closed flasks, ethylene is released. The rateof ethylene release appears to be dependent on the levels oflight and CO₂ available for photosynthesis in the tissues. In Xanthium the rate of ethylene release is lower in the lightthan in the dark regardless of the presence or absence of addedbicarbonate as a source of CO₂. The inhibition of ethylene releaseis most apparent in the absence of added bicarbonate (i.e. atthe CO₂ compensation point), and at light intensities sufficientto saturate photosynthesis (had the CO₂ level in the test flaskbeen maintained). In contrast, light dramatically promotes therate of ethylene release from Zea leaf tissue when the CO₂ levelis maintained above the CO2 compensation point. The rate ofethylene release from either Xanthium or Zea, incubated withor without added bicarbonate, does not appear to be alteredby further increasing the light intensity above the minimallevels sufficient to saturate photosynthesis. In the closed system used in these studies and at a light intensitysufficient to saturate photosynthesis, Xanthium and Zea leaftissue both appear to release comparable amounts of ethylenefrom ACC when the data is expressed on a chlorophyll basis.However, in Xanthium the rate of ethylene release is similarin light and dark, while in Zea the rate in the light is muchgreater than in the dark when the data is expressed either ona leaf area or on a chlorophyll basis. It is suggested thatthe different responses of these tissues to light/dark transientsmay reflect differences in their ability to metabolize ACC and/ordifferences in their ability to retain and metabolize ethyleneitself.     

In-Phase Cycling of Photosynthesis and Conductance at Saturating Carbon Dioxide Pressure Induced by Increases in Water Vapour Pressure Deficit

Bunce, J. A. 1987. In-phase cycling of photosynthesis and conductanceat saturating carbon dioxide pressure induced by increases inwater vapour pressure deficit.—J. exp. Bot. 38: 1413–1420. The leaf to air water vapour deficit was increased suddenlyfrom about 1·0 to 2·5 IcPa for single leaves ofsoybean (Glycine max L. Merr.) plants held at 30 °C, 2·0mmol m ^–2 s^–1 photosynthetic photon flux density(PPFD) and carbon dioxide pressures saturating to photosynthesis.After a lag of about 10 min, photosynthetic rate and stomatalconductance to water vapour began to decrease, and then cycledin phase with each other. The period of the cydes was about20 min. During these cycles the substomatal carbon dioxide pressurewas constant in the majority of leaves examined, and was alwaysabove saturation for photosynthesis. Epidermal impressions showedthat most stomata changed in aperture during the cycles, andthat very few were ever fully closed. Water potential measuredon excised discs changed by at most 0·1 MPa from theminima to the maxima in transpiration rate. In contrast, forleaves of sunflower (Helianthus animus L.) grown at low PPFD,the increase in VPD led to leaf wilting and decreased photosynthesis,followed by recovery of turgor and photosynthesis as stomatalconductance began to decrease. In these leaves photosynthesisand conductance then cycled approximately 180° out of phase.It is suggested that in soybeans decreased leaf conductanceinduced by high VPD provided a signal which decreased the rateof photosynthesis at carbon dioxide saturation by a mechanismthat was not related to a water deficit in the mesophyll. Key words: Photosynthesis, stomatal conductance, cycling, vapour pressure deficit     

Sulphate Transport into Plants and Excised Roots of Soybean (Glycine max L.)

The rates of sulphate transport into intact and excised rootsof soybean (Glycine max L.) were not significantly differentin the first hour and were maximal at pH 7. However, intactroots accumulated four times as much sulphate as excised rootsin 24 h, because of a marked reduction in the rate of transportby excised roots. The continued high rates of transport intointact roots were observed in plants kept in the light, andobserved in darkened plants growing in 1 per cent sucrose. Similarly,sulphate accumulation by excised roots was stimulated 2-foldby 1 per cent sucrose. The characteristics of sulphate accumulation by roots were notuseful in predicting sulphate translocation to the leaves. Transportto the leaves was maximal at pH 2–3, was almost totallylight-dependent and was not enhanced by growing plants in sucrose. Sulphate transport, Glycine max L., soybean, excised roots