Vessel element formation in cultured carrot-root phloem slices

The effects of light, auxin and cytokinin on vessel elementformation in phloem slices of carrot root were examined. When slices of carrot cultivars, ‘Nakamura-senko-futo’and ‘Yamada-hyakunichisenk6- naga’, preculturedin the dark on modified Murashige and Skoog's medium for twodays were cultured on a medium containing 5x10^–6 M 2,4-Din the dark, no vessel element formation occurred. When preculturedslices were cultured in the light with 5x10^–6M 2,4-D,vessel element formation was remarkable. But when 5x10^–7Mkinetin, benzyladenine or zeatin was added, vessel elementswere readily formed even in the dark. When slices were cultured in the light, a cytokinin-like substance(s)that causes vessel element formation was produced in the slices,then was released to the medium. The substance(s) was fairlystable to heat. In slices of carrot cultivars, kuroda-gosun, ‘Kintoki’and ‘Kokubu-senk6-6naga’, a different result forvessel element formation was obtained. When slices of thesecultivars were cultured on a medium containing 5x10^–6M2,4-D in the dark, vessel element formation was remarkable.It seemed, therefore, that these cultivars contain enough ofa cytokinin-like substance(s) to form vessel elements. In fact,vessel element forming activity was found in the alcohol extractof carrot root phloem from these cultivars. (Received June 8, 1971; )     

Effect of Inorganic Phosphate on the Biosynthesis of Purine and Pyrimidine Nucleotides in Suspension-Cultured Cells of Catharanthus roseus

The levels of purine and pyrimidine nucleotides in suspensioncultures of Catharanthus roseus were determined 24 h after stationary-phasecells were transferred to fresh complete (‘+Pi’)or phosphate-deficient (‘–Pi’) Murashige-Skoogmedium. The levels of ATP, GTP, UTP and CTP were from approx.3 to 5-fold greater in the cells grown in ‘+Pi’medium than in the cells grown in ‘–Pi’ medium.The levels of almost all other nucleotides were slightly higherin the cells in ‘+Pi’ medium. The rates of de novoand salvage biosynthesis of purine and pyrimidine nucleotideswere estimated from the rates of incorporation of radioactivityfrom [¹⁴C]formate, [2–¹⁴C]glycine, NaH¹⁴CO₃, [6–¹⁴C]orotate,[8–¹⁴C]adenine, [8–¹⁴C]adenosine, [2–¹⁴C]uraciland [2–¹⁴C]uridine. The results indicated that the activityof both the de novo and the salvage pathway was higher in thecells in ‘+Pi’ medium than in the cells in ‘–Pi’medium. The rate of degradation estimated from the rate of releaseof ¹⁴CO₂ from labelled purines and pyrimidines indicated thatdegradation of uridine was significantly reduced in the cellsin ‘+Pi’ medium, but no significant difference wasfound in the degradation of adenine, adenosine and uracil. Thepossible role of Pi in the control of the biosynthesis of nucleotidesand in the degradation of uridine is discussed. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, nucleotides, purines, pyrimidines, biosynthesis, degradation     

Enzymic Maceration of Citrus Callus and the Regeneration of Plants from Single Cells

The maceration medium comprised a basal nutrient medium (BM)containing an optimum concentration of 3% (w/v) sucrose. Mannitoland sorbitol were inferior osmotica. Addition of potassium dextransulphate adversely affected maceration. ‘Macerozyme’was not as effective as ‘Macerase’ in the productionof single cells. The optimal concentration of ‘Macerase’was found to be 2–3% (w/v). Single cells obtained by filtering the macerate were rinsedwith BM and cultured in, and on, agar media comprising: BM;BM + 500 mg 1^–1 malt extract (ME); and BM + 10% (v/v)coconut milk (CM). No growth or organization was observed incultures where cells were mixed in with warm medium prior togelling. When spread on the surface of gelled media supplementedwith ME and CM, proliferation and organization occurred. Manymicroscopic globular proembryoids developed within 3 weeks onthe supplemented media. Microscopic torpedo-shaped embryoidswere frequently observed on BM + CM, rarely on BM + ME, andnot at all on unsupplemented BM. The high frequency of microscopic globular proembryoids, andlater of macroscopic pseudo-bulbils, formed on BM + ME leadsus to postulate that pseudobulbils are derived from globularproembryoids in which polarity is not established by the 16to 32-cell stage. Microscopic torpedo-shaped embryoids probablygive rise to macroscopic heart-shaped embryoids which developinto plantlets. The technique reported in this article provides an ideal systemfor examining embryogenesis per se and for studying the effectsof various treatments on embryogenesis and organ differentiationin vitro. It also affords excellent opportunities for the breedingof solid mutant plants.     

Ontogenesis, Differentiation and Precocious Germination in Anther-derived Somatic Embryos of Grapevine (Vitis vinifera L.): Proembryogenesis

Histological steps of callogenesis and proembryogenesis in anthercultures ofVitis vinifera L. ‘Grenache noir’ aredescribed. Embryogenic calli were obtained on Nitsch and Nitschmedium supplemented with 1mgl^-12,4-dichlorophenoxyacetic acid(2,4-D) and 0.25mgl^-1benzylaminopurine (BAP). Calli were initiatedfrom anther connective cells only and no division of microsporesoccurred. The embryos were hence of somatic origin. Proembryosdeveloped either directly (i.e. without intervening callus)from the endothecium, or indirectly from the connective-derivedcallus. In both cases, proembryos originated from single cells.They developed from starchy differentiated cells of a predeterminedtype. The polarity of the somatic proembryo was establishedfrom the first divisions and it was marked by precocious developmentof an easily recognizable suspensor. Other analogies with thedevelopment of the zygote are also emphasised. Vitis vinifera L.; grapevine; somatic embryogenesis; proembryogenesis; histology     

Anther Culture of Lolium temulentum, Festuca pratensis and Lolium x Festuca Hybrids. I. Influence of Pretreatment, Culture Medium and Culture Incubation Conditions on Callus Production and Differentiation

This study was conducted with Lolium temulentum, Festuca pratensis,and the two hybrids L. multiflorum x F. pratensis ‘Elmet’and L. perenne x F. pratensis ‘Prior’. In a comparisonof various durations (7–42 d) of pretreatment at 4 or7 °C the highest yield of microspore-derived callus of L.temulentum was obtained after pretreatment of spikes at 7 °Cfor 28 d, conditions which also proved optimal for panicle pretreatmentwith F. pratensis. For ‘Elmet’, durations of 21–42d were optimal, and for ‘Prior’ the responses tendedto decline with increasing duration. In L. temulentum addition of charcoal (1–2 g l^–1)to medium containing 2, 4-D and KN wa     

The Uptake of Growth Substances: X. THE ACCUMULATION OF PHENOXYACETIC ACID AND 2,4-DICHLOROPHENOXYACETIC ACID BY SEGMENTS OF AVENA MESOCOTYL

Segments of Avena mesocotyl were placed in buffered solutionsof phenoxyacetic acid (POA) or 2,4-dichlorophebnoxyacetic acid(2,4-D), containing carbon-14 in the carboxyl group, and thequantities of radioactivity taken up by the tissues measured.With freshly cut segments in solutions of 2,4-D there is accumulationof carbon-14, but the course of uptake is interrupted by a temporaryphase when some of the accumulated 2,4-D is released to theexternal solution. If after cutting the segments are first pretreatedby placing them for about 15 h in buffer, and then transferredto 2,4-D, there is progressive accumulation with no phase ofnet loss. Pretreated segments absorb greater quantities of either 2,4-Dor POA than freshly excised tissues. Following pretreatmentin buffer the course of uptake of POA is linear but for 2,4-Dthe course is curvilinear. However, after pretreatment withnon-radioactive 2,4-D the subsequent rate of uptake of radioactive2,4-D is constant over long periods. The uptake of radioactive2,4-D is largely independent of the concentration of non-radioactive2,4-D given during pretreatment. When segments which have absorbed 2,4-D-1-¹⁴C are transferredto buffer, a relatively small proportion of the carbon-14, the‘mobile fraction’, is released. The amount releasedfollowing different periods of uptake is constant whereas thelevel of non-mobile carbon-14, the ‘residual fraction’,rises progressively in step with accumulation. The uptake of POA and 2,4-D is accompained by the formationwithin the tissues of other radioactive substances. It is concludedthat the residual fraction is composed, at least in part, ofthese metabolic products and that accumulation and metabolicconversion are inter-connected. Dinitrophenol (DNP) slowly and progressively depresses the uptakeof POA whereas the uptake of 2,4-D is very rapidly arrested.However, after about 2 h, in the continued presence of DNP,uptake of 2,4-D restarts but the rate never attains that ofthe control. These divergent effects of DNP indicate that POAand 2,4-D are accumulated by different pathways.     

Plantlet Production from Morphogenetically Competent Cell Suspensions of Daylily

Cell suspensions of the diploid daylily cultivar Autumn Blazewere produced from larger masses of tissue by culture in thebasal medium of Murashige and Skoog supplemented with 10 percent v/v coconut water and 2 mg 1^–12,4–D. By drasticallylowering the level of 2,4–D, followed by transferral toa modified White's or Schenk and Hildebrandt medium, clustersgrow and ultimately give rise to embryonic structures. A finalperiod in a semi-solid medium stimulates shoot and root growthto the point where successful transplanting of plantlets tosoil is assured provided safeguards to prevent ‘dampingoff’ and desiccation are taken. Normal plantlet formationmay be arrested in the formation of neomorphs which do not seemper se to be capable of further development but they can giverise to morphologically normal plantlets after they are stimulatedto form callus which, in turn, is given an appropriate sequenceof stimuli. Hemerocallis, daylily, totipotent cells, micropropagation, tissue culture.     

The Respiration Rate of Tomato Stem Tissue Infected by Tomato Aucuba Mosaic Virus

The oxygen uptake of stem tissue slices of Lycopersicum esculentumvar. ‘Stonor's Moneymaker’, in 0·035 M. Sorensonphosphate buffer was measured manometrically; the optimum pHwas found to be 5·2. With tomato-stem tissue systemicallyinfected by virus (tomato aucuba mosaic), the respiration ratewas always below that of healthy tissue when equal numbers ofrespiratory systems were compared. When the respiration ratewas expressed in terms of oxygen uptake per unit fresh or dryweight, the respiration rate of the virus-infected tissue couldbe greater or less than that of the healthy tissue dependingon the growth conditions of the experimental material. Underconditions favouring the complete development of disease symptoms,virus infection decreased the fresh and dry weight of the cell.For this reason fresh weight and dry weight were not consideredsuitable criteria to express the respiration rates as theseunits contained different numbers of respiratory systems inhealthy and virus-infected tissue.     

The Growth of the Coffee Berry

In Kenya the coffee berry stays in the ‘pin-head’stage for approximately 6–8 weeks after flowering. A periodof rapid growth follows which ends when the berry is about 17weeks old. Thereafter, a small loss of fresh weight seems tooccur while the dry weight remains constant for about two weeks.At this stage the beans have attained their final size but drymatter can be as low as 9 per cent. Until the time when ripeningbegins, the fresh weight of the berry increases little whilethe dry weight increases regularly. In this period dry weightis laid down mainly in the beans which attain their final dryweight when the berry is still green. During ripening of theberry (which is in fact ripening of the pulp) the fresh weightof the beans drops slightly due to loss of water. Both freshweight and dry weight of the pulp (including parchment) increaseconsiderably during ripening by approximately 121 per cent.and 106 per cent. respectively.     

Purification of an Auxin-Binding Protein from Etiolated Mung Bean Seedlings by Affinity Chromatography

An auxin-binding protein with high affinity for 2,4-D and IAAwas purified from the extract of etiolated mung bean seedlingsby affinity chromatography on 2,4-D-linked Sepharose 4B andby gel nitration on Sepharose 4B. Its molecular weight was estimatedto be about 390,000 by gel nitration on Sepharose 4B and itconsisted of two different subunits with molecular weights ofabout 47,000 and 15,000. This protein had no ribulose-l,5-bisphosphatecarboxylase activity. Its dissociation constants for 2,4-D andIAA were 9.3 x 10^–6 M and 3.2 x 10^–6 M, respectively,as determined by Scatchard's method. (Received December 21, 1982; Accepted March 23, 1983)     

Effects of 2-Chloroethylphosphonic Acid on Growth, Plastid Pigments, and Sucrose Translocation in Radish

2-Chloroethylphosphonic acid (CEPA) caused a significant declinein chlorophyll content of radish plant within 5 d of treatment.Such effects were greater when plants were treated at the two-than at the four-leaf stage. In early treated plants, concentrationof CEPA increasing from 20 mg/1 progressively increased leafweight, while decreasing root (radish) weight. A concentrationof 10 mg/1, applied at the three-leaf stage, increased leafand root weights by 27 and 30 per cent respectively in the cultivar‘Cavalier’. Similar responses were obtained withthe cultivar ‘Cherry Belle’. While Cavalier showeda discrete 10 mg/1 optimum, ‘Cherry Belle’ exhibiteda range of concentrations (10-40 mg/1) optimal for growth. At relatively high concentrations, early application of CEPAcaused inverse changes in sucrose-¹⁴C in the leaves and theroot, so that decreased retention by leaves was accompaniedby increased transport to roots. Low concentrations of CEPAappear promising for growth stimulation in root-crop plants.     

The Influence of the Plant Growth-regulator, 2-Methyl-4-Chlorophenoxyacetic Acid, on the Metabolism of Carbohydrate, Nitrogen and Minerals in Solanum lycopersicum (Tomato)

The effects of the foliar application of phytocidal concentrationsof 2-methyl-4-chlorophenoxyacetic acid (MCPA) on change in totaldry weight, and in ‘available carbohydrate’ (starch,‘total’ and ‘reducing’ sugars), totalnitrogen, phosphorus, potassium, calcium, and magnesium of ‘tops’and roots of tomato plants have been followed over a periodof 14 days following spraying. There were two main treatments—‘nutrient’(nutrient supply to roots continued after spraying) and ‘water’(distilled water only supplied to roots after spraying) and‘water’ (distilled water only supplied to rootsafter spraying)—the sub-treatments consisting of ‘MCPA’versus ‘no-MCPA’ for each of the main treatments.Twelve different times of sampling were used. In analysing the present data, the quantity ‘residualdry weight’ (total dry weight less ‘available carbohydrate’),which was originally introduced by Mason and Maskell as a basisof reference for analyses of plant organs in short-period experimentsnot involving appreciable growth, has been used as an estimateof the permanent structure of plant growth. This new use ofthe ‘residual dry weight’ basis has brought outimportant features which were obscured when the data were leftin their primary form (as percentages of total dry weight oramounts per plant). Growth, as measured by increase in ‘residual dry weight’,was greatly inhibited by 2-methyl-4-chlorophenoxyacetic acidshortly after spraying, in both the presence and the absenceof nutrient. In the presence of 2-methyl-4-chlorophenoxyacetic acid, netassimilation rate (estimated as rate of increase in total dryweight per gram ‘residual dry weight’ of the ‘tops’)was greatly diminished while uptake of total nitrogen and ofP₂O₅ (estimated as increase in total nitrogen or of P₂O₅ ofthe whole plant per day per 1 g. ‘residual dry weight’of the roots) appeared to undergo a similar but much smallerdiminution. It seemed probable, however, that in the presenceof MCPA a larger proportion of the carbohydrate actually formedwas utilized for synthesis of aminoacids and protein. In the plant as a whole there was no evidence of actual depletionof ‘available carbohydrate’ as a result of MCPAtreatment, this fraction showing a steady increase in all treatmentsthroughout the experiment. The rate of increase was, however,much reduced by MCPA treatment. The ‘tops’ presentedmuch the same picture as the whole plant, but for the rootsthe situation was quite different. While the roots of the ‘no-MCPA’plants and also of the ‘MCPA-water’ plants showeda steady increase in available carbohydrate, those of the ‘MCPA-nutrient’plants rose only very slightly (from the initial value of 8mg. per plant to about 10 mg.) during the first 2 days, andthen in the next 2 days declined to a value (about 6 mg.) belowthe initial and remained at this low level for the rest of theexperiment. It is suggested that the phytocidal effect of 2-methyl-4-chlorophenoxyaceticacid in the presence of nutrient may be due to depletion ofthe ‘available carbohydrate’ supplies in the roots,which is shown to be brought about, in part, by reduced transportfrom the tops, and partly by the relatively greater utilizationof the carbohydrate present. These results offer an explanationfor the facts that plants showing vigorous growth are more easilykilled by MCPA and that perennial plants, particularly thosewith storage tissues in their roots, are more resistant. Further,they suggest the useful practical application that MCPA treatmentshould be given when the carbohydrate reserves of the rootsare at a minimum. For perennial plants, conditions might beexpected to be optimal for the application of MCPA in late spring,at a time when the first ‘flush’ of growth is slowingdown and before any appreciable new reserves of carbohydratehave been accumulated. It was also shown that 2-methyl-4-chlorophenoxyacetic acid preventedthe net synthesis of starch, but still permitted an appreciablenet formation of sucrose. 2-methyl-4-chlorophenoxyacetic acid appeared to have no effecton the uptake of potassium, calcium, or of magnesium. The lackof effect on potassium is contrasted with the previous observationby Rhodes, Templeman, and Thruston (1950) that sub-lethal concentrationsof MCPA, applied over a relatively long period to the rootsof tomato plants, specifically depressed the uptake of potassium.     

Regulation of Storage Protein Synthesis by Sulphur and Nitrogen Nutrition in Cultured Immature Caryopses of Barley

Techniques are described for the culture of developing barley(Hordeum vulgare L.) caryopses. Over a 7 d period in culturethe dry weights and the amounts of starch and protein increasedby at least twofold. Growth was sustained for at least 20 d.The effects of glutamine and cysteine on the amount and compositionof the hordein storage proteins were also studied. Glutaminestimulated total hordein accumulation but caused a disproportionateincrease in the amount of the S-poor ‘C’ hordeinswhen supplied at 100 mol m^–3. Addition of cysteine at1·0 mol m^–3 did not increase the amount of Srich‘B’ hordeins. The results suggest that althoughisolated caryopses are able to take up sucrose and glutamineand convert them to starch and protein there is some limitationin their ability to convert externally supplied cysteine intoproteins. Key words: Hordeum vulgare L., Caryopses, Glutamine, Cysteine, Storage proteins     

Pattern of Respiration of a Perennial Ryegrass Crop in the Field

‘Dark’ respiratory losses of CO₂ were measured ona one year old sward of S24 perennial ryegrass (Lolium perenneL.) at intervals during a 74 day reproductive growth period,between April and June, and a 21 day vegetative growth period,in July and August. Part of the sward was shaded for one weekbefore measure ments commenced. Measurements of ‘dark’respiration continued for 46 hand it was possible to distinguishtwo components which are designated ‘maintenance’and ‘synthetic’ ‘Maintenance’ respiration was taken to be the meanrate of CO₂ efflux after 40–46 h darkness. When calculatedon a plant d. wt basis at 15°C it ranged between 6 to 32mgCO₂ g^-1 day^-1 during reproductive growth and 10–14 mgCO₂ g^-1 day^-1 during vegetative growth. During reproductivegrowth, sward protein content ranged between 7–23 percent and when maintenance respiration was recalculated on thebasis of protein content it changed relatively little throughoutthe growth period (90–140 mg CO₂ g pro tein^-1 day^-1);the value for vegetative growth ranged between 70–100mgCO₂ g protein-day^-1. Total ‘synthetic’ CO₂ flux was determined duringreproductive growth and a rate of ‘synthetic’ CO₂flux was determined during both reproductive and vegetativegrowth. Between 15 and 35 per cent of the CO₂ fixed in the previousphotoperiod was lost in ‘synthetic’ respirationof above-ground material in reproductive swards. Previous shadingincreased the proportion of ‘synthetic’ CO₂ lossfrom above ground. The rate of ‘synthetic’ CO₂ outputduring the first hours of darkness increased with amount ofCO₂ fixed in the previous photoperiod, although it was not proportionalto it. There is some evidence that assimilate is ‘carried-over’from one photoperiod to the next.     

Polyamine Content in Relation to Embryo Growth and Dedifferentiation in Barley (Hordeum vulgare L.)

Putrescine, spermidine, and spermine content were analysed inzygotic embryos of barley (Hordeum vulgare L.). Changes in polyaminecontent were observed during zygotic embryo growth. In two cultivars,‘Bomi’ and ‘Golden Promise’, the totalpolyamine content in the embryos was 2.6–2.9 nmol mg^–1fresh weight 10 d after anthesis, the highest content observed.It dropped to 1.3 nmol mg^–1 fresh weight 14 d after anthesis.This drop was caused by decreases in all three polyamine concentrations.From 14 to 35 d after anthesis the putrescine content continuedto decrease while the spermidine and spermine content increased,thus the total polyamine content remained constant until 35d after anthesis. The mutant ‘Ris? 1508’ showeda constant polyamine content around 1.3 nmol mg^–1 freshweight from 14 to 35 d after anthesis. The polyamine patternwas conserved in all three lines throughout the period of investigationshowing a spermidine content higher than putrescine contentwhich was, in turn, higher or equal to the spermine content.The polyamine content measured as nmol µg^–1 proteindecreased from 14 to 21 d post anthesis in all three lines,because the protein content (µg mg^–1 fresh weight)increased during the period. In dedifferentiating zygotic embryoscultured in vitro the putrescine content (nmol mg^–1 freshweight) rose by a factor of nine and the spermidine contentdoubled within the first week of cultivation, whereas sperminecontent did not change. For embryoderived calli a repeated patternof change in polyamine content was observed throughout the subculturingperiod. Key words: Polyamines, Hordeum vulgare L., embryo development     

The Photosynthetic Net Carbon Dioxide Exchange Potential in Conventional and 'Leafless' Phenotypes of Pisum sativum L. in Relation to Foliage Area, Dry Matter Production and Seed Yield

The effect of the ‘leafless’ mutation (in whichtendrils replace leaflets and the stipules are reduced to avestigial form) upon foliage area, photosynthetic net CO₂ uptakepotential, dry matter production and seed yield in Pisum sativumwas studied by comparing two near-isogenic lines of genotypeafafstst and ++++. The mutation is of potential agronomic valuein that it offers improved lodging resistance, crop drying andharvester throughput. In the conventional phenotype the total foliage area of themain axis attained a plateau (456 cm²) at day 56 from seedlingemergence, whereas corresponding values for the ‘leafless’mutant showed a total area of 208 cm² at day 68 with no indicationof a plateau. The agronomic consequence of this is discussed.During the vegetative phase of the plant the maximum CO₂ uptakepotential in the fully expanded conventional leaf was 8·5mg CO₂ leaf^–1 h^–1 and in the ‘leafless’mutant this value was 7·0 mg CO₂ leaf^–1 h^–1.For most ‘leaves’ of the latter phenotype this valuewas between 30 and 60 per cent less than for their conventionalcounterpart. There was a consistently higher photosyntheticpotential per unit area in tendrils of the ‘leafless’mutant than in leaflets of the conventional phenotype. The respectivemean specific values for the two phenotypes were 53 and 37 mgCO₂ dm^–2 h^–1. The problem of obtaining a meaningfulsurface area value for tendrils is discussed and the cylindricalnature of tendrils is taken into account. The ‘leafless’ mutant consistently accumulated 50per cent less dry matter than did conventional plants in theperiod from seedling emergence to anthesis and yield of maturedry seed per plant showed a reduction of 50 per cent both inseed number and total seed weight. The implications for future breeding and selection programmesaimed at haulm reduction are discussed in relation to evaluatingthe ability of the background genotype to produce adequate tendrilsin the presence of afafstst. Triticum aestivum, wheat, callus culture, organogenesis     

Nitrogen Fixation, Assimilation and Transport During the Initial Growth Stage of Phaseolus vulgaris L

In nodulated common bean (Phaseolus vulgaris L.), there is typicallya period of N stress between 15 and 20 d after emergence (DAE),due to a lack of synchronization between the depletion of Nin the cotyledons and the beginning of N² fixation and transport.Screening trials identified some Rhizobium leguminosarum bv.phaseoli strains with which symptoms of N deficiency were notvisible (‘precocious’ strains). Cultivar Negro Argelwas then inoculated with two ‘traditional’ strains(C-05 and CIAT 727) and two ‘precocious’ strains(CNPAF 146 and CNPAF 512), and plants were harvested from 8to 30 DAE. There were no differences between the two groupsof strains in nodule dry weight or in the acetylene reductionrates between 8 and 16 DAE. However, nodules induced by the‘precocious’ strains showed earlier onset of glutaminesynthetase (GS) (EC 6.3.1.2 [EC] ) and glutamate synthase (GOGAT)(EC 1.4.1.14 [EC] ) activities, and ureide synthesis. The N concentrationin the nodules formed by ‘precocious’ strains variedfrom 4.2 to 4.5%, whereas with the ‘traditional’strains, it increased from 3.2% at 8 DAE to 65% at 18 DAE, atwhich time plants exhibited N-deficiency symptoms. By 21 DAE,GS and GOGAT activities in ‘traditional’ noduleswere increased, as well as the ureide-N-concentration in thexylem sap, nodule N content declined to 4.5% and the leavesbecame green. These results suggest that the N stress with ‘traditional’strains is not a limitation in early N² fixation activity butrather in the rates of expression of the processes of N assimilationand transport. Key words: Glutamate synthase, glutamine synthetase, nitrogen fixation, Phaseolus vulgaris, Rhizobium     

Effects of Monochromatic Radiations on Growth of Pelargonium Callus Tissue

Pith callus tissues were grown under continuous blue (450 mµ),green (545 mµ), red (650 mµ), and ‘white’(full-spectrum) light, and in the dark for 22 days at 27±2°C at energy levels of 15,000 ergs cm^–2 sec^–1. Mean increases in fresh weight of tissues grown under ‘white’and blue light were significantly greater than those of tissuesgrown in green and red light and in the dark. Tissues grownin the dark yielded mean fresh weight increases significantlylower than tissues grown under blue, red, and ‘white’light. No significant differences were shown between blue and‘white’, red and green, and green and dark treatmentsrespectively. Cell differentiation occurred in all treatmentsonly to the extent of vessel element formation. There were nodifferences in degree of differentiation between treatments. It was proposed that the high-energy reaction of photomorphogenesiswas in operation in the Pelargonium callus tissue. The resultsindicated the presence in the tissue of high-energy photoreceptor(s).The use of high-intensity, incandescent illumination for experimentalprocedures approximating natural conditions of irradiation wasindicated as desirable for pith callus tissues of Pelargoniumzonale var. Enchantress Fiat.     

Ethylene and Ethane Production in 2,4-D Treated and Salt Treated Tobacco Tissue Cultures

Gas chromatography was used to measure ethylene (ethene) andethane production by tobacco (Nicotiana tabacum cv. Wisconsinno. 38) callus tissues grown on media containing inorganic saltsaccording to Murashige and Skoog (1962), sucrose, myo-inositol,thiamine-HCl kinetic according to Linsmaier and Skoog (1965),and either 2,4-dichiorophenoxyacetic acid (2,4-D) in the range0–100 mgl^–1 or 2 mgl^–1 indoi-3-ylacetic acidplus NaCl in the range 0–200 Meq l^–1. Ethylene productionrates were high (> 500 nl h^–1 g^1– fresh weight)initially in all treatments. Subsequently, ethylene productiondeclined in rapidly growing cultures but remained high in moderatelyand severely 2,4-D (> 0·5 mgl^–1) stressed andin severely NaCl (150 Meql^–1) stressed cultures. Highinitial rates of ethane production (> 200 nl h^–1 g^–1fresh weight) were obtained under conditions of severe stresscaused by 2,4-D or NaCl but not in control or moderately inhibitedcultures. With further incubation ethane production declinedin the severely stressed cultures. It is concluded that ethyleneproduction can be used as an index of moderate 2,4-D stressand severe NaCl stress by virtue of the high persisting ratesof ethylene production in stressed cultures. Ethane productioncan be used as an early index of severe stress caused by either2,4-D or NaCl in vitro. Nicotiana tabacum L., tobacco, ethylene, ethenen, ethane, 2,4-dichlorophenoxyacetic acid, auxin, stress, callus tissue     

Morphogenesis of 2,4-D Induced Abnormalities of the lnflorescence of Bread Wheat (Triticum aestivum, L.).

Treatment of Triticum plants with 2,4-D profoundly affects inflorescencemorphogenesis and results in the production of various abnormalities,amongst which are branched heads, whorls of spikelets. superimposedpairs of spikelets (‘banana’ twin spikelets) andpaired spikelets borne at the same level (‘yoked’spikets). Often more than one kind of abnormality is observedin a single head. Except for ‘banana’ twin spikelets,none of the induced abnormalities are duplicated by abnormalitieswhich occur spontaneously in untreated plants. Disturbance dueto treatment is only temporary and later the terminal regionof the apex recommences growth along a normal pattern of morphogenesis.