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.     

Statistical method for predicting protein coding regions in nucleic acid sequences

Protein coding regions of a genome fragment can be mathematicallypredicted by studying variations in the statistical propertiesor by searching the signals characteristic of the junctionsbetween the coding and non-coding regions. We propose here anew statistical method using correspondence analysis. This methoddoes not use any reference codon set but takes into accountthe codon usage homogeneity along the studied genome fragment.Comparison with previously published methods especially the‘codon usage method’ of Staden has been made, andtwo examples are presented here. Applications to analysis ofprokaryotic operon and eukaryotic split genes are also discussed.Use of the method has also shown two structures not previouslydescribed: i) in the human prt gene, a strong triplet structureexists in a non-coding region; ii) in the human tp-a codon usageis not uniform between the different exons Received on September 25, 1986     

Notes on Contagious Distributions in Plant Populations

Past experience has shown that the Poisson series is often inadequateas a model for describing plant populations. Various alternativetwo-parameter models have been suggested in place of the Poissonseries, but they all depend on assumptions which may or maynot hold. In this paper a different approach is put forwardin that attention is concentrated on the mean number of plantsper quadrat and an index of ‘clumping’ or ‘contagiousness’.Examples are given as to the use of these concepts to test fordifferences between the distribution of a plant in two localitiesor between two plants in the same locality.     

The Metabolism of 3-Indolylacetic Acid in Plant Tissues3

The nature of metabolic products of 3–indolylacetic acid(IAA) extracted from potato tuber disks treated with aeratedIAA solution has been investigated. Two major products, knownat first as ‘V’ and ‘P’ in these studieshave been isolated and ‘V’ has been identified as3-indolylacetylaspartic acid (IacAsp). The rapid uptake of IAA is inhibitited by metabolic poisonssuch as 10^–3 M. cyanide. The maximum mean internal concentrationexceeds the external concentration well–aerated cultures.The mean internal concentration, however only remains for aperiod and then falls off rapidly as a result of extrusion ofabsorbed IAA into the external solution. This extrusion is notinhibited by 10^-3 cyanide; when the mean internal IAA concentrationis 150 µ mol/ml. and the localized IAA concentration musttherefore exceed this value. We conclude therefore that theIAA concentration in the sites where it has accumulated exceedsthe concentration of IAA outside. Uptake of IAA and also its further conversion are inhibitedby indolylacetonitrile and promoted by aspartate, but this promotionis not associated with any gain in amount of indolylacetylaspartate(IacAsp). The data suggest that IacAsp may be formed in tissue from ‘boundIAA’ rather then free IAA. The ‘accelerator ’ found in potato and beans whichhas similar R_F to IAcAsp has been shown definity to be someother substance or substances and not IAcAsp as was at firstthought possible.     

Integrated Analysis of Growth and Light Interception in Winter Lettuce II. Differences between Cultivars

‘Integrated growth analysis’ (emphasizing aspectsof crop and plant structure) and ‘light conversion analysis’(stressing the efficiency of interception and photosyntheticconversion of light) have been used to investigate the wintergrowth of different cultivars of butterhead and crisphead typesof glasshouse lettuce. Measurements from ‘Ambassador’ (large-framed butterhead),‘Renate’ (medium-sized butterhead) and ‘Cristallo’(crisphead) were made, statistical progressions were fittedto the primary data and hence estimates of all the analyticalcomponents were derived. Curves for crop growth rate, like those for most other components,followed a generally similar pattern for all three cultivars.In integrated growth analysis, the biomass curve for Ambassadorlay above the curves for the other cultivars. The weight advantagewas initially 60 per cent and it persisted with only a smallreduction (to 40 per cent) until the final harvest. Relativegrowth rate varied little between cultivars because differencesobserved in leaf area ratio were complementary to those seenin net assimilation rate. In light conversion analysis, differences in light interceptingefficiency between cultivars were not statistically significant,though Ambassador attained full interception 4 days earlierthan Renate and 6 days earlier than Cristallo. Differences inlight utilizing efficiency were small and non-significant exceptduring the post-rosette stage when the value for Renate waslower than that of either Ambassador or Cristallo. Deviationsaround the fitted curves were correlated with fluctuations inthe light regime. An assessment is made of the utility and limitations of thetwo procedures. It is concluded that both approaches can assistin analyzing the rate of dry matter production in crops or plantstands. Integrated growth analysis is advantageous when theneed arises to treat individual and population-based attributessimultaneously, while light conversion analysis provides a meansof explicitly incorporating the primary environmental variableinfluencing growth. Lactuca sativa L., lettuce cultivars, growth analysis, crop growth rate, relative growth rate, light interception, light utilization     

The growing outer epidermal wall: design and physiological role of a composite structure

Background: The cells of growing plant organs secrete an extracellular fibrouscomposite (the primary wall) that allows the turgid protoplaststo expand irreversibly via wall-yielding events, which are regulatedby processes within the cytoplasm. The role of the epidermisin the control of stem elongation is described with specialreference to the outer epidermal wall (OEW), which forms a ‘tensileskin’. Novel Facts: The OEW is much thicker and less extensible than the walls ofthe inner tissues. Moreover, in the OEW the amount of celluloseper unit wall mass is considerably greater than in the innertissues. Ultrastructural studies have shown that the expandingOEW is composed of a highly ordered internal and a diffuse outerhalf, with helicoidally organized cellulose microfibrils inthe inner (load-bearing) region of this tension-stressed organwall. The structural and mechanical backbone of the wall consistsof helicoids, i.e. layers of parallel, inextensible cellulosemicrofibrils. These ‘plywood laminates’ containcrystalline ‘cables’ orientated in all directionswith respect to the axis of elongation (isotropic material).Cessation of cell elongation is accompanied by a loss of order,i.e. the OEW is a dynamic structure. Helicoidally arranged extracellularpolymers have also been found in certain bacteria, algae, fungiand animals. In the insect cuticle crystalline cutin nanofibrilsform characteristic ‘OEW-like’ herringbone patterns. Conclusions: Theoretical considerations, in vitro studies and computer simulationssuggest that extracellular biological helicoids form by directedself-assembly of the crystalline biopolymers. This spontaneousgeneration of complex design ‘without an intelligent designer’evolved independently in the protective ‘skin’ ofplants, animals and many other organisms.     

The Effects of Salinity upon Galactosyl-Glycerol Content and Concentration of the Marine Red Alga Porphyra purpurea (Roth) C.Ag.

Changes in the major alcohol-soluble, low molecular weight carbohydratesof P. purpurea, O--D-galactopyranosyl-(1-2)-glycerol (‘floridoside’)and O--D-galactopyranosyl-(1-1)-glycerol (‘isofloridoside’),have been examined in response to salinity variation. ‘Floridoside’is shown to vary in absolute amount, increasing in hypersalineand decreasing in hyposaline media. ‘Isofloridoside’content per cell does not change in a similar manner. Responsesare almost identical under light or dark conditions, ‘floridoside’changes being complete within 24 h. Decreasing the externalwater potential using ionic and non-ionic solutes has the sameeffect upon galactosyl-glycerol content. The amount of ‘floridoside’synthesized, and degraded under hypersaline and hyposaline conditionsrespectively is shown to be insufficient to restore cell volumeto its original value. It is therefore suggested that the primaryfunction of ‘floridoside’ increases in concentratedsea-waters is that of a compatible solute, serving to protectthe cell during periods when the external salt content is increaseddramatically.     

Evaluating the 'Labeled Magnitude Scale' for Measuring Sensations of Taste and Smell

The Labeled Magnitude Scale (LMS) is a semantic scale of perceptualintensity characterized by a quasi-logarithmic spacing of itsverbal labels. The LMS had previously been shown to yield psychophysicalfunctions equivalent to magnitude estimation (ME) when gustatory,thermal and nociceptive stimuli were presented and rated together,and the upper bound of the LMS was defined as the ‘strongestimaginable oral sensation’. The present study comparedthe LMS to ME within the more limited contexts of taste andsmell. In Experiment 1, subjects used both methods to rate eithertaste intensity produced by sucrose and NaCl or odor intensityproduced by acetic acid and phenyl ethyl alcohol, with the upperbound of the LMS defined as either the ‘strongest imaginabletaste’ or the ‘strongest imaginable odor’.The LMS produced psychophysical functions equivalent to thoseproduced by ME. In Experiment 2 a new group of subjects usedboth methods to rate the intensity of three different tastequalities, with the upper bound of the LMS defined as the ‘strongestimaginable [sweetness, saltiness, or bitterness]’. Inall three cases the LMS produced steeper functions than didME. Experiment 3 tested the hypothesis that the LMS yields datacomparable to ME only when the perceptual domain under studyincludes painful sensations. This hypothesis was supported whenthe LMS again produced steeper functions than ME after subjectshad been explicitly instructed to omit painful sensations (e.g.the ‘burn’ of hot peppers) from the concept of ‘strongestimaginable taste’. We conclude that the LMS can be usedto scale sensations of taste and smell when they are broadlydefined, but that it should be modified for use in scaling specifictaste (and probably odor) qualities. The implications of theseresults for theoretical issues related to ME, category-ratioscales and the size of the perceptual range in different sensorymodalities are discussed. Chem. Senses 21: 323–334, 1996.     

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.     

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     

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.     

Effects on Growth and Development of Individual Chromosomes from Slow-growing Lophopyrum elongatum Love when Incorporated into Bread Wheat (Triticum aestivum L.)

Aspects of growth and development were evaluated in the fast-developingannual Triticum aestivum L. ‘Chinese Spring’, theslow-developing perennial Lophopyrum elongatum Löve, theiramphiploid, and chromosome addition and substitution lines ofL. elongatum into ‘Chinese Spring’. Relative growthrates (RGR) of shoots of L. elongatum and the amphiploid werelower than those of ‘Chinese Spring’ (34 and 13%respectively) and main stem development was also slower. Therewas no difference in shoot RGR of any of the chromosome additionor substitution lines and that of ‘Chinese Spring’when assessed between Haun stages 2.0 and 5.0. In contrast,several aspects of plant development were observed to differin the chromosome addition and substitution lines. SubstitutingE genome chromosomes (with the exceptions of 3E and 4E) forD genome chromosomes, or adding E genome chromosomes, slowedthe rate of main stem development, at least up to Haun stage5.0. Despite these differences in the rate of main stem development,the appearance of adventitious roots commenced at approximatelyHaun stage 2.0 in all genotypes. However, the numbers of adventitiousroots and tillers at the 5.0 Haun stage differed between someof the lines when compared to ‘Chinese Spring’.Although incorporation of some L. elongatum chromosomes alteredaspects of plant development, all lines showed more similarityto bread wheat than to L. elongatum, reflecting, in part, thegreater genetic contribution made by bread wheat to these lines.Copyright 2001 Annals of Botany Company Adventitious roots, chromosome addition and substitution lines, Haun stage, Lophopyrum elongatum, relative growth rate (RGR), Triticum aestivum(wheat)     

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.     

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     

Data Analysis and Graphics Using R: An Example-Based Approach, Second Edition. * John Maindonald and John Braun

A volume in the ‘Cambridge Series in Statistical and ProbabilisticMathematics’, ‘Data Analysis and Graphics UsingR’ is presented as a gentle tour guide for new R users,aiming to help them navigate through many powerful tools thatthe open source R system offers. As the authors point out inthe Preface, the book is ‘aimed at scientists who wishto do statistical analysis on their own’. Every efforthas been made to ensure the book is useful for practical dataanalysis. This book is particularly useful for researchers inthe life science realm who     

Hybrid Identification in Clivia(Amaryllidaceae) using Chromosome Banding and Genomic In Situ Hybridization

Giemsa C-banding and genomic in situ hybridization (GISH) wereused to identify parental genomes in hybrids of Clivia(Amaryllidaceae).Of the three groups reputed to be hybrids, onlyC. cyrtanthiflorawas shown to be of hybrid origin. The ‘German hybrids’and ‘Belgian hybrids’ were both shown to be karyotypicallyand genomically similar to C. miniata, and are either selectionsor intraspecific hybrids of that species. Successful genomedifferentiation in F₁hybrids by GISH required high stringencyand high ratios of blocking DNA to probe. The spatial dispositionof different genomes with C-band or GISH markers in the hybridswas investigated in two dimensions on the spread. In five artificiallyproduced hybrids, either C-banding or GISH was used to locatethe position of parental genomes in mitotic metaphase cells.In all cases there was a significant tendency for centromeresof the different parental genomes to occupy two distinct concentricdomains on the metaphase plate. The presence or absence of centromericheterochromatin was not correlated with genome disposition.Results show that chromosome analyses can be a useful way ofidentifying Clivia hybrids in their vegetative phase. Copyright2001 Annals of Botany Company Clivia, genomic in situ hybridization, cultivar origin, parental genome separation     

Studies in the Physiology of the Onion Plant: V. AN INVESTIGATION INTO THE GROWTH SUBSTANCE CONTENT OF BULBING ONIONS

Extracts have been prepared from induced and non-induced onionplants. These extracts have been fractionated and the ether-soluble,acidic components investigated using the wheat coleoptile straight-growthassay, colorimetric determination of 3-indolylacetic acid (IAA),and a new bioassay which has been introduced and modified togive reproducible results. This last is an assay of substanceswhich will cause ‘bulbing’ (swelling of the leafbases) of onion plants, and it has been used to demonstratea number of factors which influence the initiation of bulbingin the onion. It has been shown that substances are presentin extracts of onion tissue which will cause an increase inthe ‘bulbing ratio’ of test onion seedling sections. Results indicate that there is an increase in the IAA contentto a very high level during the first week following induction—beforethere is any visible sign of swelling of the leaf bases—butthat this falls off rapidly after 5–7 days and eventuallyfalls below the level found in non-induced plants.     

Concentration-dependent changes of perceived odor quality

In order to assess the dependence of perceived odor qualityon odorant concentration, we studied 21 subjects. For eightsubjects all possible pairs from a pool of six odorants at threedecimal dilutions were presented, and subjects were requestedto state whether members of the pair were qualitatively ‘similar’or ‘different’ It was found that while pairs withthe same odorant at identical concentrations were judged ‘similar’in >90% of the cases by all subjects, scores went down to10% ‘similar’ judgements in some cases when thesame odorant was presented at a 100-fold concentration difference.Large time-invariable differences were found among subjectsand among odorants. For the additional 13 subjects, all possiblepairs from a pool of four odorants at three decimal dilutionswere presented. Subjects were instructed to state whether membersof the pair were qualitatively ‘same’ or ‘different’,and were also requested to rank the degree of difference ona visual analogue scale. Results for this group were, in general,similar to the results of the former group of subjects and goodagreement between the two tasks was found. The results suggestthat variations in olfactory stimulus magnitude may be perceivedas quality differences, as previously shown for vision and audition.     

Effects of Flooding and Drainage and their Alternation on the Growth and Uptake of Nutrients by Rice (Oryza sativa L., indica, var. IR-8)

Continuous flooding of the soil (‘flooded’ treatment)gave best growth of IR-8 variety of rice whereas soil drainedfor 4 weeks and then flooded for 8 (‘drained and flooded’treatment) resulted in poorest growth and chlorotic plants.Plants grown in the continuously drained soil (‘drained’treatment) and those in the soil flooded for 4 weeks and thendrained for 8 (‘flooded and drained’ treatment)showed intermediate growth. There were no differences in therelative water content of plants growing in the various treatments.Analyses of plant tissues showed that a consideration of therelative concentration of Fe, Mn, and P in the shoots is mostclosely related to the performance of rice under various culturalconditions. An increase in the concentration of Fe in the planttissues following flooding was correlated with the best growth(‘flooded’ treatment) unless it was accompaniedby high level of Mn (as in the ‘drained and flooded’treatment) which may have proved toxic, e.g. by interferencewith Fe metabolism as was evidenced by chlorosis. Measurementsof oxidation-reduction potentials, oxygen diffusion rates, andthe concentration of exchangeable and soluble Fe and Mn in thesoils have shown that the ‘drained and flooded’treatment caused the most extreme reducing conditions. Floodingaccompanied by the development of extreme reducing conditionsled to a greater accumulation of Mn in the shoots (‘drainedand flooded’ treatment) whereas flooding accompanied bythe maintenance of oxidizing conditions (‘flooded’treatment) resulted in a lower uptake of Mn. Growth of riceplants for 4 weeks in the drained soil did not fit them forthe reduced conditions which developed during subsequent flooding(‘drained and flooded’ treatment).