The Fine Structure of Bamboo Fibres: I. OPTICAL PROPERTIES AND X-RAY DATA

Following the recent work on wood tracheides and sisal fibres,a detailed investigation has been made of the fine structureof a wide variety of bamboo fibres. A combination of X-ray analysis,measurement of refractive indices in longitudinal view and ofphase differences in transverse section, has presented a completepicture of cellulose chain orientation. The wall of bamboo fibresis many layered. An outermost, thin layer is composed of cellulosechains making an angle of 35° to cell length and this isfollowed by other, inner layers where the angle steadily decreasesfrom outer to inner layers, first to about 20° and thento about 10°. These layers are separated by thicker layers,dark in transverse section between crossed nicols, in whichthe angle is seldom more than 5–6°. These are averagefigures. The results show most clearly that each angle, , varieswith the fibre length, L, in such a way that the longer cellshave steeper spirals in harmony with a relation of the typeL=A+Bcot already proposed for wood tracheides.     

A Test for Non-randomness in Plant Populations

A simple test for non-randomness suitable for use in samplingplant populations is suggested. The criterion used is where n_i is the number of quadrats containing i shoots. A tablegiving significant points of for various values of N, the totalnumber of quadrats, is provided. The test is applied to four sets of experimental data and theresults agree with tests carried out on the complete distributions.It is suggested that this type of criterion could be used inother fields where similar forms of non-randomness also exist.     

The Time Factor in Studies of Growth Inhibition in Excised Organ Sections

1. Apprehension over the adequncy of current techniques stimulateda detailed study of the time factor in the arsenate inhibitionof growth and respiration in excised stem and root sectionsof Pisum sativum.
2. Growth inhibition by arsenate sets in veryslowly, its rateof onset being related to the molar concentration(C) of arsenateate by the relation where T₅₀ is the time taken in hours to reduce the growthrateto 50 per cent of the control and K is a constant. An explanationof the physiological basis of this relationship is attempted.
3. Estimates were made of the final steady growth rate (relativeto control) in various arsenate concentrations. The inhibitionscalculated from this rate are held to approximate to the truearsenate effect and are shown to be very different from thosecalculated from ‘total growth’ measures.
4. Respirationof growing stem sections is not inhibited by thelow arsenateconcentrations that inhibit growth. Some inhibitionis indicatedat high concentrations (3 ? 10^–4M. and over)but onlyafter 15-20 hours of exposure.
5. Two per cent sucrose has noeffect on the arsenate inhibiitionof stem growth. Sucrose,however, markedly stimulates respirationin stem sections, butthis stimulation is prevented by arsenate.
6. The misinterpretationswhich may arise as a result of ignoringthe time factor in inhibitionstudies in excised organ sectionsare discussed and the desirabilityof constructing completegrowth curves in all such studies isstressed.

     

Physiological Studies in the Mucorales: PART II SOME OBSERVATIONS ON GROWTH REGULATION IN THE SPORANGIOPHORE OF PHYCOMYCES

Lanolin emulsion paste incorporating indolylacetic acid in concentrationsof 10,000, 1,000, 100, and 10 µg./ml when applied witha micromanipulator to one side of Phycomyces sporangiophoreshad no clearly marked action on subsequent growth Griseofulvin, a metabolic product of Penicillium janczewskiiand certain other moulds, at a concentration of 1OO µg./ml.,produced a local increase in the rate of extension of the wallat or near the region to which it was similarly applied, withconsequent curvature from the normal erect growth habit. Previously proposed explanations of the regulation of sporangiophoregrowth, and of phototropism, in terms of the action of heteroauxinand auxin- are criticized, and attention directed to the dangerof assuming that substances active in regulating the growthof cellulose-walled times will have a similar action on chitin-walledfungal hyphae.     

Carbon Dioxide Fixation by Barley Roots

The non-volatile, 80 per cent.ethanol-soluble products of fixationhave been investigated in excised roots, using C^14O₂ and radiochromatography. The main radioactive compounds separated were malic, citric(or iso-citric), aspartic, and glutamic acids, asparagine andglutamine. Less activity was present in serine, tyrosine, -ketoglutaricacid, and alanine, and in a number of unidentified compounds. The uptake of C^14O₂ was inhibited by virtually anaerobic conditions. From the above observations it is considered likely that C¹⁴is transformed through the reactions of the tricarboxylic acidcycle. C¹⁴ in the soluble fraction was markedly increased by maintainingthe root material in water rather than in a nutrient solutionprior to exposure to C^14O₂ This increase was chiefly in malicacid.     

The Assimilation of Ammonia by Nitrogen-starved Cells of Chlorella vulgaris: Part II. The Assimilation of Ammonia to other Compounds

Ammonia is rapidly assimilated by nitrogen-starved Chlorellacells and converted into soluble organic nitrogenous compounds.During the first 20 minutes of assimilation most of the ammoniawhich has been used can be accounted for as free or combined-amino-nitrogen and amide-nitrogen. Later a smaller proportionof the assimilated ammonia is found in these fractions whileappreciable quantities of basic amino-acids are formed. Theassimilation of ammonia is accompanied by an increase of therates of oxygen absorption and carbon dioxide production; thevalue of the respiratory quotient decreases. Non-reducing sugarand acid-hydrolysable polysaccharide are metabolized rapidly. Possible interpretations of these facts are discussed.     

Microbiological Synthesis of Fat: PRELIMINARY SURVEY OF THE FAT-PRODUCING MOULDS

1. A survey of potential fat-producing moulds has shown that atleast 40 strains from 10 species are of interest.
2. These havebeen grown on five different media and A. nidulans,P. spinu-losum,P. javanicum, P. piscarium, P. flavo-cinereum,P. oxalicum,A. flavus, A. flavipes have shown the most promise.
3. The fatcontent on felt weight was maximal at 39?7 per cent,with A.flavipes and 34?6 per cent, with F. lini, and on usedsugarwas maximal at 9?3 per cent, with A. flavipes and 6?7per cent,with A. nidulans.
4. The potential value of micro-organisms asfat producers is discussedwith reference to the moulds.

     

Metabolism of Slices of the Tomato Stem

The rate of respiration of tomato stem slices varied considerably,the highest values (Qo₂, 2–3) being obtained for plantsin a good nutritional state, and the lowest (Qo₂, 1) in starvedplants. The respiratory quotient of 1.0 remained constant. Glucose fermentation was found to follow both glycolytic andalcohol fermentation pathways, the ratio of ethyl alcohol: lacticacid being 6.6:1. Fermentation seems to take place accordingto the Embden-Meyerhof scheme, as shown by the presence of someof these enzymes operative in this scheme and by inhibitionexperiments. In the presence of oxygen there was no formationof alcohol or lactic acid. Pyruvate added to tomato stem slices was metabolized by directoxidation to acetic acid and by dismutation to lactic and aceticacids and CO₂ The metabolism of acetic acid was demonstratedby its condensation with oxaloacetic acid to form citrate, thisbeing the second time that synthesis of citric acid by thismechanism has been found in plants. The presence of aconitase,of isocitric dehydrogenase, of succinic dehydrogenase, and ofmalic dehydrogenase, as well as the inhibition of respirationby malonic acid, favour the hypothesis that oxidation of carbohydratein tomato stem slices proceeds via the citric acid cycle. Thepossibility of an auxiliary route, the malic acid oxidationpathway, also was demonstrated. Tomato stem tissue anaerobicallysplit malic acid into glycolic acid. The further oxidation ofglycolic, glyoxylic, and formic acid was demonstrated. In experiments with C¹⁴-labelled acetate and butyrate a dilutionof the C¹⁴-labelled acids was found after incubation indicatingnew formation of these acids and of active participation offatty acid metabolism in the metabolic activities of the tissue. With the exception of alanine, added amino acids produced adefinite increase in O₂ uptake without extra formation of ammonia. Experimental demonstration of the possibility of electron transportfrom substrate to molecular oxygen in respiration via polyphenoloridase was provided by the attainment in a tomato tissue homogenateof a coupled oxidation-reduction between -ketoglutarate andcatechol with DPN and tyrosinase as the catalysts. The presenceof cytochrome oxidase was also demonstrated. Thus both systemspossibly may take part in the respiration of tomato stem slices.     

The Analysis of the Alcohol-insoluble Nitrogen of Plants by Quantitative Procedures based on Paper Chromatography

Part I. The amino-acid composition of egg albumin, zein, edestin,cucumber (Cucumis) seed globulin, and squash (Cucurbita) seedglobulin has been determined by a quantitative paper chromatographicmethod. The chromatographic analyses account completely forthe amino-acid nitrogen of the protein hydrolysate as determinedby the Kjeldahl method. More complete analyses than hithertoof cucumber and squash seed globulin have been obtained. Theseanalyses can now be regarded as complete since histidine andtryptophane, which have not been determined chromatographically,have previously been reported. The two cucurbit seed globulinsanalysed closely resemble edestin, and evident differences betweenthese three on the one hand and zein on the other are referredto in the text. It is evident that the paper chromatographicmethod is applicable to the quantitative amino-acid analysisof the protein-N fraction of the plants as well as to the analysisof pure proteins. Part II. The analysis of the alcohol-soluble and insoluble fractions(hydro-lysate) of potato tubers of the variety ‘Sebago’has been carried out. Attention is drawn to differences whichexist between the samples and varieties which have been investigated,namely ‘King Edward’, ‘Sebago’, and‘Katahdin’. These differences relate particularlyto the relative proportion of soluble to insoluble nitrogen,to the amount of amides present in the soluble fraction, andto the ratio of asparagine to glutamine. There is no correlation between the relative proportions ofamino-acids as they exist free in the tuber and as they occurin the alcohol-insoluble (protein) fraction. Certain compounds(e.g. -aminobutyric acid) are present free in the tissue, butthey do not occur in the protein. Also the amides far exceedtheir possible occurrence combined in the protein. Proline especiallyis much more abundant in the combined than in the free state,and the ratios between the various free amino-acids are quitedifferent from those which apply to the protein. The latterdata suggest that the soluble compounds which occur free arenot directly combined as such to form protein. The utility of the quantitative procedure based on partitionchromatography on paper in the analysis of the alcohol-insoluble(protein) fraction of plants is, therefore, established.     

Studies on Plant Growth Hormones: II. FURTHER BIOLOGICAL PROPERTIES OF 3-INDOLYLACETONITRILE

1. 3-Indolylacetonitrile is more active than 3-indolylacetic acidin the Avena straight-growth test, but less active in the Avenacurvature test at comparable concentrations. Reasons for thisare discussed, and results of previous work on plant extractsusing the curvature test as a means of assay are considered.
2. Transport of both the acid and the nitrile is polar, fromapexto base of the coleoptile. The nitrile can reach the growingcells as easily, and possibly more easily, than the acid. Thesignificance of these findings for a theory on the mechanismof action of the nitrile is discussed.
3. The nitrile is inactivein the pea curvature test and straight-growthof pea stem sectionsexcept at high concentrations. It is alsoinactive or only slightlyactive in lateral bud inhibition,root initiation, and petioleabscission at the concentrationstested.
4. It is less activethan the acid in root inhibition in cress,but approximatelyas active in Avena. It is approximately asactive as the acidin parthenocarpic fruit development, andinitiation of cambialactivity.
5. The significance of these results is discussed.

     

The Metabolism of Glucose and Acetate in Aspergillus niger

1. The metabolism of a citric-acid-forming strain of A. nigerwhengrown on a glucose-acetate medium has been investigated.
2. Acetate greatly accelerated the rate of utilization of glucose.
3. Citric acid production from glucose was much increased bythepresence of acetate.
4. The formation of oxalate from glucose-acetatecultures was muchless than from acetate alone.
5. In some cultureslarge amounts of glucose and acetate were consumedbut no acidicproducts were formed.

     

Factors concerned in the Rooting Responses of Isolated Leaves

The rooting responses of isolated leaves of the dwarf Frenchbean and the ivy were studied by applying solutions of growthsubstances to the petiole: ß-indolyl-butyric acid(I.B.A.) for the former and -naphthyl-acetic acid (N.A.A.) forthe latter. The following factors were investigated:

1. The variation in response of successive leaves from the apextowards the base of the plant.
2. The optimal concentrationsof the growth substances and therelation between duration ofapplication and concentration.
3. The relation of age of theleaf and optimal concentration(ivy).
4. The nutritive factorsconcerned in the response were studied,(a) by varying periodsof contact between lamina and petiole,(b) by varying durationof light, (c) by varying the amountof light, and (d) by feedingwith sucrose and asparagine.

The most responsive leaf in the bean was the 2nd from the apex,in the ivy the 9th leaf. Very young leaves were killed. Withpetioles immersed for 24 hours the optimal concentrations wereI.B.A. at 2·5 parts per million (p.p.m.) for the bean,and N.A.A. 100 p.p.m. for the ivy. It was shown that the activesubstance entered mainly through the cut end in the transpirationstream; entry through the cuticle was much slower. Starvation of the cuttings whether by low light intensity, darkness,or separation of the lamina from the petiole reduced root formation.Feeding with sucrose and asparagine increased the response. Analysis of the leaves was carried out at regular intervalsfor total sugar, total and soluble nitrogen. In the bean solublenitrogen increased slightly in the petiole during the first5 days after treatment, after which insoluble nitrogen continuedto accumulate until the 7 day, when the roots first emerged.After this the total nitrogen decreased. Sugar content of thepetiole at first increased but rapidly fell before the rootsemerged and then again increased. In the ivy petiole the increasein soluble and total nitrogen was very slow, the former beinggreatest on the 15th day and the latter on the 20th day aftertreatment. The total sugar increased to the 10th day, but thendecreased until the emergence of roots, after which it againincreased. Treated leaves of the bean and ivy of different agesand the leaves starved for varying periods were also analysedfor total sugars and total nitrogen. Treated bean leaves receivingvarying periods of daily illumination were also analysed toelucidate their rooting response. Histological examination showed that in the bean the roots arosein the rays between the vascular bundles and in the ivy externalto the vascular bundles opposite the phloem. The growth of the rooted leaves was followed for more than amonth in the bean and over one year in the ivy. Some growthwas found in the immature bean leaves which survived treatment,but the final size was much below that of the control leavesattached to the plant. In the ivy very little further growthoccurred although the leaves produced a large root system andafter 2 years are still alive: the original differences in sizeof the successive leaves at the time of removal from the plantstill remain.     

Organic Acid Metabolism of Sedum praealtum

1. The organic acids present are citric, isocitric, and l-malic,with a small residue of unidentified acids.
2. The diurnal variationin acidity is due chiefly to changes,in malic acid, with aparallel fluctuation shown by citric acid.Under these conditionsisocitric acid shows little change.
3. The importance of carbondioxide during acidification is confirmed,and it is shown thatat room temperatures or higher the CO₂produced in respirationis sufficient to produce maximum acidification.At lower temperaturesthe supply of CO₂ limits acid production.
4. In the absence ofoxygen no acidification occurs, but even smallquantities (approx.1 per cent.) are sufficient to cause someacid production.
5. Completebalance-sheets are presented for acids, carbohydrates,CO₂ andoxygen for leaves maintained in the dark at high andlow temperatures.As acids are produced there is a correspondingloss of carbohydrate(chiefly starch). A scheme of reactionsis suggested to explainthe experimental results.

     

Nuclear DNA Content as an Index Character Discriminating Taxa in the Genus Petunia sensu Jussieu (Solanaceae)

Nuclear DNA contents over the total range of the genus Petuniasensu Jussieu comprising 20 taxa of Petunia sensu Wijsman (2n = 2 x = 14) and 32 taxa of Calibrachoa(2 n = 2 x = 18) wereestimated by flow cytometry after staining the nuclei with propidiumiodide (PI) or 4',6-diamidino-2-phenylindole (DAPI). With respectto nuclear DNA content, taxa of Petunia sensu Wijsman seemedto be homogeneous (2C = 2.60 to 3.41 pg), but Calibrachoa taxawere clearly separated into two groups: (1)C. parviflora andC. pygmaea(1.56 to 1.91 pg); and (2) remaining members of Calibrachoa(2.84to 3.26 pg). Taxa of Petunia sensu Wijsman exhibited largerPI/DAPI ratios (relative fluorescence intensity with PI stainingto that with DAPI staining) than Calibrachoa species exceptC.parviflora and C. pygmaea. This suggests that Petunia sensuWijsman has nuclear DNA with more adenine-thymine rich regionsthan Calibrachoa. Copyright 2000 Annals of Botany Company Calibrachoa, 4',6-diamidino-2-phenylindole (DAPI), flow cytometry, nuclear DNA content,Petunia , PI/DAPI ratio, propidium iodide (PI), Solanaceae     

Photosynthesis and Light Activation of Ribulose 1, 5-bisphosphate Carboxylase in the Presence of Starch

Owing to a typographical error three equations were omittedfrom page 1294. The correct paragraphs are set out below. The component K₁ corrected for the difference in temperaturebetween the enzyme assay and the leaf and was calculated accordingto the Arrhemus equation. where v10 and v18 are the reaction velocities of carboxylationat 10?C and 18?C, respectively and A is the activation energy(A = 90 kJ mol^–1, as determined for purified wheat RuBPCOby M?chler, Keys and Cornelius, 1980) The components K2 corrected for the difference in CO₂ partialpressure between enzyme assay and leaf and for competitive inhibitionof carboxylation by O₂ and was calculated according to the modifiedMichaelis Menten equation where v_c, is the carboxylation velocity under leaf conditions,V_c. is the maximum carboxylation velocity as determined in theenzyme assay, K_c, and K_o are the Michaelis constants for carboxylationand oxygenation, respectively (K_o = 159 Pa CO₂. K_o = 35.3 kPaO₂, as interpolated for 18?C from spinach data as determinedby Jordan and Ogren, 1984), O is oxygen partial pressure inair and C₁ is intercellular CO₂ partial pressure in leaves (C₁= 29.1 ? 0.8 Pa (? s c , n = 15)) The component K3 corrected for the decrease in CO₂ fixationin leaves due to photorespiration and was calculated accordingto equation 3 Equation 3 is denved from the equation for the substrate specificityof RuBPCO, S= v_c/v_oC (Laing, Ogren, and Hageman, 1974), andfrom the equation for the stoichiometry of photorespiratoryCO₂ release, F=v_c–1/2 v_o, where v_c, and v_c are reactionvelocities of carboxylation and oxygenation, O and C are partialpressures of 02 and intercellular CO₂, F is net photosynthesisand S is the substrate specificity of RuBPCO (S= 3061 Pa/Pa,as interpolated for 18?C from spinach data as determined byJordan and Ogren, 1984)     

Calcium dependence of C-type natriuretic peptide-formed fast K+ channel

The lipid bilayertechnique was used to characterize theCa²⁺ dependence of a fastK⁺ channel formed by a synthetic17-amino acid segment [OaCNP-39-(1-17)] ofa 39-amino acid C-type natriuretic peptide (OaCNP-39) found in platypus (Ornithorhynchusanatinus) venom (OaV). TheOaCNP-39-(1-17)-formed K⁺ channel was reversiblydependent on1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-buffered cis (cytoplasmic)Ca²⁺ concentration([Ca²⁺]_cis).The channel was fully active when[Ca²⁺]_ciswas >10⁴ M andtrans (luminal)Ca²⁺ concentration was 1.0 mM, butnot at low[Ca²⁺]_cis.The open probability of single channels increased from zero at1 × 10⁶ McisCa²⁺ to 0.73 ± 0.17 (n = 22) at10³ McisCa²⁺. Channel openings to themaximum conductance of 38 pS were rapidly and reversibly activated when[Ca²⁺]_cis,but not transCa²⁺ concentration(n = 5), was increased to >5 × 10⁴ M(n = 14). Channel openings to thesubmaximal conductance of 10.5 pS were dominant at5 × 10⁴ MCa²⁺.K⁺ channels did not open whencisMg²⁺ orSr²⁺ concentrations were increasedfrom zero to 10³ M or when[Ca²⁺]_ciswas maintained at 10⁶ M(n = 3 and 2). The Hill coefficientand the inhibition constant were 1 and 0.8 × 10⁴ McisCa²⁺, respectively. Thisdependence of the channel on high[Ca²⁺]_cissuggests that it may become active under1) physiological conditions whereCa²⁺ levels are high, e.g., duringcardiac and skeletal muscle contractions, and2) pathological conditions that leadto a Ca²⁺ overload, e.g., ischemicheart and muscle fatigue. The channel could modify a cascade ofphysiological functions that are dependent on theCa²⁺-activatedK⁺ channels, e.g., vasodilationand salt secretion.

     

Genetic diversity and geographic differentiation in endangered Ammopiptanthus (Leguminosae) populations in desert regions of northwest China as revealed by ISSR analysis

• Background and Aims The desert legume genus Ammopiptanthuscomprises two currently endangered species, A. mongolicus andA. nanus. Genetic variability and genetic differentiation betweenthe two species and within each species were examined. • Methods Inter-simple sequence repeat (ISSR) marker datawere obtained and analysed with respect to genetic diversity,structure and gene flow. • Key Results Despite the morphological similarity betweenA. mongolicus and A. nanus, the two species are geneticallydistinct from each other, indicated by 63 % species-specificbands. Low genetic variability was detected for both populationlevel (Shannon indices of diversity H_pop = 0·106, percentageof polymorphic loci P = 18·55 % for A. mongolicus; H_pop= 0·070, P = 12·24 % for A. nanus) and specieslevel (H_sp = 0·1832, P = 39·39 % for A. mongolicus;H_sp = 0·1026, P = 25·89 % for A. nanus). Moderategenetic differentiation was found based on different measures(AMOVA _ST and Hickory ^B) in both A. mongolicus (0·3743–0·3744)and A. nanus (0·2162–0·2369). • Conclusions The significant genetic difference betweenthe two species might be due to a possible vicariant evolutionaryevent from a single common ancestor through the fragmentationof their common ancestor's range. Conservation strategies forthese two endangered species are proposed.     

Ca2+-activated Cl- current in cultured myenteric neurons from murine proximal colon

Whole cell patch-clamprecordings were made from cultured myenteric neurons taken from murineproximal colon. The micropipette contained Cs⁺ to removeK⁺ currents. Depolarization elicited a slowly activatingtime-dependent outward current (I_tdo), whereasrepolarization was followed by a slowly deactivating tail current(I_tail). I_tdo andI_tail were present in ~70% of neurons. Weidentified these currents as Cl currents(I_Cl), because changing the transmembraneCl gradient altered the measured reversal potential(E_rev) of both I_tdo andI_tail with that for I_tailshifted close to the calculated Cl equilibrium potential(E_Cl). I_Cl areCa²⁺-activated Cl current[I_Cl(Ca)] because they were Ca²⁺dependent. E_Cl, which was measured from theE_rev of I_Cl(Ca) using agramicidin perforated patch, was 33 mV. This value is more positivethan the resting membrane potential (56.3 ± 2.7 mV), suggestingmyenteric neurons accumulate intracellular Cl.-Conotoxin GIVA [0.3 µM; N-type Ca²⁺ channelblocker] and niflumic acid [10 µM; knownI_Cl(Ca) blocker], decreased theI_Cl(Ca). In conclusion, these neurons haveI_Cl(Ca) that are activated by Ca²⁺entry through N-type Ca²⁺ channels. These currents likelyregulate postspike frequency adaptation.

     

The Effect of Prolonged Chilling on Water Movement and Radial Growth in Trees

1. The woody shoots of young saplings of Fraxinus.excelsior andAcer Pseudo-platanus in pots were subjected to continuous coolingto about 2° C. during the growth season, with the resultthat radial growth was almost completely inhibited throughoutthe woody stem.
2. The chilling did not adversely affect extensiongrowth exceptthat it was later in commencement and proceededmore slowly.
3. If the temperature around the stem is loweredfrom 2° C.to 0° C., water conduction is cut down tosuch an extentas to cause wilting of the leafy shoots; turgidityis recoveredwhen the temperature is again raised to 2°C.
4. This wilting effect is discussed particularly in relationtothe part played by living cells in the upward movement ofwaterin the wood.