The Pattern of Protein Accumulation in Relation to DNA Replication in Jerusalem Artichoke Callus Cultures

While the synchronous first division cycle in cultured explantsfrom Jerusalem artichoke tubers may vary in duration from oneto two days the length of the ‘S’ phase of thiscycle remains approximately constant at 14 h. A study of thepattern of protein accumulation in relation to this ‘S’phase shows the development of three different populations ofcells in an initially uniform explant. Cells from the centreof the explant accumulate neither DNA or protein while cellsin the peripheral layers accumulate protein according to thesame pattern irrespective of whether they synthesize DNA ornot. This similarity between dividing and nondividing cellsis of interest in considering cellular events leading to celldivision.     

Effect of large- and of small-bodied zooplankton on phytoplankton in a eutrophic oxbow

Macrozooplankton and microzooplankton effects on the phytoplanktonwere measured in situ in a eutrophic lake. Indigenous phytoplanktonwere incubated for 5 days in 301 mesocosms with either the macro-and microzooplankton (complete), microzooplankton only (micro)or no zooplankton (none). Changes in phytoplankton biovolumewere investigated. Rotifer densities became significantly higherin the ‘micro’ treatment than in the ‘complete’and ‘none’ treatments. Total algal biovolume changedlittle in the ‘complete’ and ‘none’treatments, but increased significantly in the ‘micro’treatment. The results suggest that macrozooplankton (Daphniamagna) suppressed it and microzooplankton (Keratella cochlearis)enhanced it. They had opposite net effects on the phytoplankton.Suppression of microzooplankton by Daphnia probably had an indirectnegative effect on the phytoplankton.     

Theodoropoulos, D.I. Invasion biology. Critique of a pseudoscience.

The back cover of this book states that ‘contrary to theclaims of the nativists, research shows that man-dispersed speciesincrease biological diversity, benefit ecosystems, and act asan important force for healing the planet’. This is anuncompromising statement, and David Theodoropoulos divides hisdevelopment of the arguments supporting this statement intothree parts. Part I (Chapters 1–6) is ‘Nature, Dispersaland Reaction’. Part II (Chapters 7 and 8) is ‘Why?Psychology, Politics and Pseudoscience’. Part III (Chapters9–11) is ‘Humanity and Diversity’. There isalso an ‘Introduction’ including a summary of findingsand ‘An outline for a new theory of anthropogenic dispersal’,     

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.     

Effect of Cultivar, Temperature and Seed Size on the Germination and Emergence of Soya Beans (Glycine max (L.) Merr.)

The rapid and uniform establishment of soya bean [Glycine max(L.) Merr.] stands is conducive to higher yields. This studywas undertaken to determine the effects of cultivar, temperature,and seed size on the rate of germination and emergence. No cultivar effect on the germination rate was observed. However,in an emergence study from a sand-soil-peat mixture, cultivardifferences in emergence rates were noted(‘Chippewa 64’> ‘Wayne’ > ‘Amsoy 71’). In anotheremergence study (sand media) the cvs ‘Calland’ and‘Williams’ emerged faster than the cv. 'Wayne or‘Wells’. Time required for 50 per cent germination decreased (18.8–4.0days) as the temperature increased from 10 to 30 °C (5 °Cincrements). Emergence (50 per cent) from a sand-soil-peat mixturewas more rapid (19.8–6.3 days) as the simulated plantingdate (growth chamber set to simulate field temperatures) wasdelayed from 16 April to 15 June with an intermediate date of16 May. In addition, time required for 50 per cent emergence of thecultivars from sand decreased (793–76 h) as the temperaturewas increased from 10 to 30 °C with no decrease from 30to 35 °C. Seed size effects were apparent, with the very small seed germinatingslower than the three larger seed sizes. In the emergence studieswith both the sand and sand-soil-peat mixture there was a generaltrend toward more rapid emergence with the smaller seeds. However,the absolute differences were small. Significant cultivar x temperature interactions were observedfor the germination and emergence rates. In most cases the cultivarsmerged in terms of germination and emergence rates at temperaturesbetween 10 and 20 °C and at the higher temperatures thecultivar rankings were different from those observed at temperaturesbelow the merging point. Glycine max (L.) Merr, soya bean, seed germination, establishment of seedlings     

The Hexagonal Branching Pattern of Rhizomes of Alpinia speciosa L. (Zingiberaceae)

Alpinia speciosa L. (Zingiberaceae) is a striking example ofa plant in which an organized architectural structure fulfilsa basic functional requirement - the economical explorationand exploitation of the substrate. This rhizomatous plant spreadslaterally in a predictable manner by vegetative growth to forma clone of separated ramets. A morphological study establishes‘rules of growth’ governing the success and failureof lateral branches (sympodial units), their lengths, and theirrelative angles. The basic branching pattern of this rhizome system approximatesto that of a hexagonal grid - the most economical structuralshape that uniformly ‘samples’ a plane surface.It is shown that the significant deviation of branching anglefound in Alpinia from that required to develop an exact hexagonalnetwork will virtually eliminate aerial shoot ‘clashes’in which the placing of one aerial shoot coincides with thatof another aerial shoot, whilst at the same time enhancing thebenefits of the hexagonal system. The broader implications ofthe organised architecture of plants are emphasised. rhizome, branching pattern, architecture, productivity     

Characterization of RNA-dependent RNA Polymerases in Healthy and Tobacco Mosaic Virus-infected Tomato Plants

Healthy tomato plants were shown to contain high levels of RNA-dependentRNA polymerase activity, mainly in a ‘soluble’ form,but also partly in a ‘ bound’ form. The ‘bound’enzyme was solublized by EDTA treatment. Both forms of enzymewere partially purified and characterized. The ion and pH optimaof the two forms were identical at all stages of purification.Both enzymes exhibited uridylyl transferase activity, whichmade up 35 per cent of total incorporation. Infection with tobacco mosaic virus (TMV) increased activityof ‘soluble’ enzyme by twofold, and of solubilized‘bound’ enzyme by less than twofold. Uridylyl transferaseactivity was also increased by infection. General propertiesof the enzymes were unaltered by infection with one exception:in the presence of TMV RNA as added template, the ‘soluble’enzyme from infected plants incorporated ³H-UTP into productswith the electrophoretic properties and RNase sensitivitiesexpected for replicative form and replicative intermediate ofTMV. ‘Soluble’ enzyme from healthy plants, and solublized‘ bound’ enzyme from either healthy or infectedplants did not synthesize these products. The ‘soluble’ and solubilized ‘bound’enzymes behaved differently on ion-exchange chromatography.Under the conditions used, ‘soluble’ enzyme didnot bind to the column, whereas solublized ‘bound’enzyme did. No differences in chromatographic behaviour werefound between enzymes from healthy or infected plants. Withboth ‘soluble’ and solublized ‘bound’enzymes, the uridylyl transferase activity co-chromatographedwith the polymerase activity. Tomato, Lycopersicon esculentum, RNA-dependent RNA polymerase, tobacco mosaic virus, tobacco mosaic virus replicase     

The Extraction, Solubility, and Characterization of Two Groups of Barley Storage Polypeptides

This paper reports further studies on the characteristics ofthe storage protein fraction (hordein) of barley. Hordein consistsof two groups of polypeptides (termed ‘B’ and ‘C’)coded by two separate but linked loci. Whereas the ‘C’polypeptides are readily soluble and extracted in 60% (v/v)ethanol at room temperature, the ‘B’ group is moresoluble in, and therefore more efficiently extracted by, 50%(v/v) propan-1-ol or 45% (v/v) propan-2-ol at elevated temperaturesand in the presence of 2-mercaptoethanol. However, the mostefficient conditions for hordein extraction (50% propan-1-ol+ 2% (v/v) 2-mercaptoethanol at 60 °C) also extract somecontaminating non-hordein polypeptides resulting in an apparentlyincreased lysine content of the hordein fraction. Amino acid analysis of the purified ‘B’ and ‘C’hordein groups shows that, whereas ‘C’ hordein containsmore glutamate + glutamine, proline, and phenylalanine than‘B’ hordein, it contains only traces of lysine andsulphur amino acids in contrast to ‘B’ hordein whichcontains 0·5% lysine 0·6% methionine, and 2·5%cysteine. Equilibrium sedimentation analyses carried out on the purified‘B’ and ‘C’ groups indicates that thepreparations were reasonably monodisperse with molecular weightsof approximately 32 000 and 52 000 respectively. These valuesare considerably lower than those previously determined by SDS-PAGE.     

Diurnal Phototropism in Leaves of Lavatera cretica L. under Conditions of Simulated Solar-Tracking

Diurnal laminar reorientation was followed in solar-trackingleaves of Lavatera cretica L. under simulated conditions. Asimulated ‘sun’ was moved over the lamina in a 180?arc in the vertical plane of the mid-vein, at an angular velocityof 15? h^–1 in a regime of 12-h photoperiods. In one groupof plants the petioles of the experimental leaves were arrangedto face ‘sunrise’, while in the other they werearranged to face ‘sunset’. At ‘sunrise’,the laminae in both groups, which were inclined towards theanticipated direction of ‘sunrise’, changed theirelevation towards the rising ‘sun’, resulting inprogressive reduction in the angle of incidence (AI) of lighton the laminar surface (AI= differential between laminar and‘solar’ elevation). As a result, laminar and ‘solar’elevation converged, and laminar reorientation gradually ceased,until the ‘solar’ elevation had passed the normalto the laminar surface (AI=0?). laminar reorientation was thenresumed, but its direction was reversed to follow the directionof ‘solar’ reorientation. During most of the remaining‘day’, laminar elevation (LE) trailed that of the‘sun’ by an average of 11?-14?. Laminar reorientationthen anticipated ‘sunset’ by starting to slow down60 to 90min in advance. During the 12-h dark period, the laminareoriented towards the anticipated direction of the subsequent‘sunrise’. The time-course of nocturnal reorientationwas qualitatively different in the two groups of experimentalplants. The time-course of diurnal phototropism under naturaland simulated conditions is analysed and compared and differencesand similarities between them are discussed. Key words: Diurnal phototropism, solar-tracking, vectorial excitation     

Density distribution and size sorting in fish schools: an individual-based model

In fish schools the density varies per location and often individualsare sorted according to familiarity and/or body size. High densityis considered advantageous for protection against predatorsand this sorting is believed to be advantageous not only toavoid predators but also for finding food. In this paper, welist a number of mechanisms and we study, with the help of anindividual-based model of schooling agents, which spatial patternsmay result from them. In our model, schooling is regulated bythe following rules: avoiding those that are close by, aligningto those at intermediate distances, and moving towards othersfurther off. Regarding kinship/familiarity, we study patternsthat come about when agents actively choose to be close to relatedagents (i.e., ‘active sorting’). Regarding bodysize, we study what happens when agents merely differ in sizebut behave according to the usual schooling rules (‘sizedifference model’), when agents choose to be close tothose of similar size, and when small agents avoid larger ones(‘risk avoidance’). Several spatial configurationsresult: during ‘active sorting’ familiar agentsgroup together anywhere in the shoal, but agents of differentsize group concentrically, whereby the small agents occupy thecenter and the large ones the periphery (‘size differencemodel’ and ‘active sorting’). If small agentsavoid the risk of being close to large ones, however, smallagents end up at the periphery and large ones occupy the center(‘risk avoidance’). Spatial configurations are alsoinfluenced by the composition of the group, namely the percentageof agents of each type. Furthermore, schools are usually oblongand their density is always greatest near the front. We explainthe way in which these patterns emerge and indicate how resultsof our model may guide the study of spatial patterns in realanimals.     

The Nitrogen Content of Plants and the Self-thinning Rule of Plant Ecology: A Test of the Core-skin Hypothesis

The ‘core-skin’ hypothesis postulates that secondarilythickened plants behave energetically as an inert ‘core’covered by an active ‘skin’, the ‘skin’being two-imensional, the ‘core’ three-dimensional.This would explain the ‘self-thinning ‘or‘–3/2’ rule of plant ecology, that is, the tendencyfor log (dry weight per plant) and log (number of plants perunit area) to progress along a straight line relationship, withslope = – 3/2’. The hypothesis was tested as follows. Plant nitrogen contentwas used as an estimate of the mass of ‘skin’ perplant, and dry weight as an estimate of the mass of the ‘core’.As plants mature the slope of the relationship between y = log(mass of nitrogen per plant) and x = log (mass of dry matterper plant) is expected to decline from an initial value of 1.0towards a final value of 0.66. The intercept of the relationshipis expected to reflect the intrinsic content of ‘skin’per unit of ‘core’. Genotypic variation in thisparameter should cause genotypic differences in the maximumattainable yield of biomass per unit area. The expectations were investigated by fitting the function y= p+qx+r exp – x to 30 sets of data on plant nitrogencontent, plant weight and time in 18 different vegetables. Simplelinear regressions of y on x were fitted to more limited setsof data on weights and nitrogen contents of mature trees. Theexpectations were, with some minor exceptions, confirmed. Nitrogen, yield, plant competition, self-thinning     

Temperature Effects on Phenological Development and Yield of Muskmelon

Our goal was to construct a simple muskmelon phenology modelthat could be run with easily obtainable weather station dataand used by growers to quantify phenological development andaid in projecting harvest dates. A growth chamber experimentwas conducted with two cultivars of muskmelon (‘Gold Rush’and ‘Mission’) to determine how main vine leaf appearancerates responded to temperature. We identified three cardinaltemperatures for leaf appearance rate: the base temperature(10 °C) at which leaf appearance rate was zero; an optimumtemperature (34 °C) at which the rate of leaf appearancewas maximal; and an upper threshold temperature (45 °C)at which leaf appearance rate returned to zero. Using thesethree cardinal temperatures, we constructed a simplified thermalunit accumulator for hourly measurements of air temperature.Main vine plastochron interval (PI), thermal time to harvest,and final yield were determined for three cultivars of muskmelon(‘Explorer’, ‘Gold Rush’ and ‘Mission’)grown in the field at Overton, TX, USA, over six transplantingdates from March to June 1998. PI was calculated for each cultivarx transplanting date combination as the reciprocal of the slopeof main vine node number vs. accumulated hourly thermal units(     

The Metabolism of Fructose Polymers in Plants: VI. TRANSFRUCTOSYLATION IN LIVING TISSUE 3HELIANTHUS TUBEROSUS L.

Tracer ¹⁴CO₂ was supplied to the leaves of Jerusalem artichokeplants in the light and tissue was removed from an attachedtuber at intervals. The first compound to contain ¹⁴C in thetuber was sucrose; label next appeared in the trisaccharideI^F-fructosylsucrose, and more slowly in the higher oligo-andpolysaccharides. After 50 hours over 40 per cent. of the tracerpresent in the tuber was found in the ‘inulin’ fraction(DP>25). Degradation of the polymers showed that in the earlystages only the sucrosyl groups of the oilgosaccharides werelabelled. Later the labelling in the fructosyl residues of the‘tails’ of the oilgosaccharides increased to thelevel of that in the sucrosyl groups. The pattern in the fractionof DP> 20 did not correspond to that of the lower polymers,as the ‘tail’ appeared to become labelled first.Transfer of terminal fructosyl residues by known transfructosylaseactivity can explain the labelling of the sucrosyl residuesof the fructosan series, thus implicating this enxyme in thedistribution of fructose within the series, but the mechanismleading to ‘tail’ labelling is still obscure.     

Factors Affecting the Abscission of Reproductive Organs in Yellow Lupins (Lupinus luteus L.): III. ENDOGENOUS GROWTH SUBSTANCES IN VIRUS-INFECTED AND HEALTHY PLANTS AND THEIR EFFECT ON ABSCISSION

Extracts of small and mature-size lupin pods yielded four substancesaffecting the growth of wheat-coleoptile sections: one acidpromotor (A), two acid inhibitors(B and X), and one neutralinhibitor(Y). Inhibitor B was extremely active, however, coleoptile sectionsshowed no signs of toxic effects; they resumed growth at a rapidrate after rinsing them and adding ß-indolylaceticand (IAA) to the medium. 1 µg of IAA was required to counteractthe effect of ‘B’ extracted from 230 mg. Of tissue.On an equal fresh weight basis the inhibiting action of ‘B’in lupin pods was 500–1,500 times more potent than thatof ‘inhibitor ß’ in etiolated pea seedlings. Small pods of plants infected with pea-mosaic virus yielded3 times the amount of ‘A’ of healthy plants (equivalentto 1 µg. IAA 0.3 µg. IAA per 25 g. of tissue respectively),and approximately the amount of ‘B’. Mature podsof virus-infected plants again yielded more‘A’,but also 2? times more ‘B’ than pods of healthyplants. Healthy pods yielded more ‘A’ than virus-infectedpods, and there was no difference in ‘X’. A lupin abscission test was developed and the effects of proximaland distal application of -naphthyl acetic acid (NAA) are presented,and discussed with respect to results of other abscission tests. ‘A’ accelerated abscission when applied proximally,and delayed or prevented it when applied distally. ‘B’strongly accelerated abscission when applied in either way.A possible mechanism explaining the abscission-inducing effectof developing pods on later flowers is discussed in terms ofthe substances ‘A’ and ‘B’. The partlyprevented abscission observed on virus-infected plants was foundto agree well with the proposed mechanism.     

Properties of Mitochondria Prepared by Two Different Isolation Procedures From the Cotyledons of Germinating Bean Seedlings

Mitochondria from 1-day-old bean cotyledons were isolated bya ‘slow’ isolation procedure involving a wash andby a ‘rapid’ procedure. The mitochondria isolatedby the ‘rapid’ procedure were more tightly coupledthan those isolated by the ‘slow’ procedure. Anexogenous supply of cytochrome c or NAD was shown to improvethe activity of mitochondria isolated by the ‘slow’procedure, but not those isolated by the ‘rapid’procedure. The phosphorylative abilities of the latter weremuch greater than the former and were retained for longer periods.It was found that there was a leakage of NAD out of the mitochondria.     

Scopoletin Involvement in Post-Harvest Physiological Deterioration of Cassava Root (Manihot esculenta Crantz)

A study of the mechanism of the rapid deterioration of cassavaroots has shown that this requires the presence of oxygen andscopoletin, the latter acting, apparently, in some autocatalyticfashion. Roots from plants whose tops were pruned off some daysprior to harvest were less liable to spontaneous deterioration,but responded vigorously to the applied scopoletin, whereasroots stored for some time in the absence of O₂, so-called ‘cured’roots were no longer susceptible to exogenously-applied scopoletin.Clearly, metabolically, the two methods for prevention of deteriorationdiffer pruning may be effective due to internally-reduced scopoletinsupply or absence of some factor involved in the primary oxidation;‘curing’ may involve loss of a scopoletin precursoror inactivation of an enzyme system. Key words: Scopoletin, Manihot esculenta, Cassava, Post-harvest deterioration     

The Microelectrophoretic Behaviour of Plant Mitochondria compared with Rat Mitochondria

‘Heavy’ mitochondrial preparations of bean, cauliflower,and rat liver have been found to give unimodal distributionfor electrophoretic mobility against number of particles. ThepH-mean mobility curves were similar in form and consistentwith the mitochondrial surfaces being lipoproteins. de Duve (1959) separated ‘heavy’ and ‘light’(lysosome-rich) mitochondrial fractions from rat liver. Microelectrophoreticstudies on similar ‘heavy’ and ‘light’mitochondrial preparations from rat liver have shown the latterto consist mostly of mitochondria with some faster-moving particlestentatively identified with de Duve's lysosomes. ‘Light’mitochondrial preparations of bean showed no evidence of particlesadditional to mitochondria.     

Recalling Taste Intensities in Sweetened and Salted Liquids

The effect of training on recalling taste intensities over 6weeks was studied using an ad libitum mixing procedure. Subjectstasted sweet and salty standards labeled as ‘weak’and ‘strong’ (3 and 8% sucrose in redcurrant juice;0.4 and 1.2% NaCl in beef broth). They subsequently mixed unsweetenedand sweetened juice, and unsalted and salted broth, to producetaste intensities that corresponded to the standards. A minimumtraining (MT) group (n = 13) produced comparison stimuli bytasting and directly comparing with standards in one sessiononly; an extensive training (ET) group (n = 13) did this insix sessions before producing comparison stimuli based on memoryonly at 1 h, 1 day, 1 week and 6 weeks. An upward bias (chemicallydetermined concentrations of comparison stimuli exceeding thoseof standards) occurred at 1 day or 1 week in MT subjects for‘weak’ and ‘strong’ sweetness, and for‘strong’ saltiness, and sustained thereafter. Theupward tendency was also observed in ET subjects but was significantonly for ‘strong’ sweetness. It is important torecognize memory effects such as the one described, as theyaffect food perceptions and can be a major source of bias insensory food research. Chem. Senses 21: 29–34, 1996. ³Current address: Psychonomics Department, Utrecht University,Heidelberglaan 2, 3584 CS Utrecht, The Netherlands     

Plant Morphology: The Historic Concepts of Wilhelm Troll, Walter Zimmermann and Agnes Arber

Recent molecular systematic and developmental genetic findingshave drawn attention to plant morphology as a discipline dealingwith the phenotypic appearance of plant forms. However, sincedifferent terms and conceptual frameworks have evolved overa period of more than 200 years, it is reasonable to surveythe history of plant morphology; this is the first of two paperswith this aim. The present paper deals with the historic conceptsof Troll, Zimmermann and Arber, which are based on Goethe'smorphology. Included are contrasting views of ‘unity anddiversity’, ‘position and process’, and ‘morphologyand phylogeny’, which, in part, are basic views of currentplant morphology, phylogenetic systematics and developmentalgenetics. Wilhelm Troll established the ‘type concept’and the ‘principle of variable proportions’. Hehas provided the most comprehensive overview of the positionalrelations of plant forms. Agnes Arber started from the universaldynamics of life and attempted to describe all structures asprocesses. She paid attention to ‘repetitive branching’,‘differential growth’, and ‘parallelism’.As a result she has recently been rediscovered by developmentalbotanists. Walter Zimmermann rejected any metaphysical influenceon plant form and instead called for objective procedures. Hewas mainly interested in phylogenetic ‘character transformation’and the ‘reconstruction of genealogical lines’.Guided by the example of flower-like inflorescences, a futurepaper will deal with functional and developmental constraintsinfluencing plant forms. Recent morphological concepts (‘trialectical’,‘continuum’/‘fuzzy’, ‘processmorphology’) will be discussed and related to currentmorphological and developmental genetic research. Copyright2001 Annals of Botany Company Plant form, plant morphology, natural philosophy, homology, phylogeny, Goethe, Troll, Arber, Zimmermann, typology, character transformation, differential growth, complementarity     

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.