Studies in the Principles of Phytotoxicity: I. THE ASSESSMENT OF RELATIVE TOXICITY

The biological effects of phytotoxic compounds will be dependentupon uptake, the amounts reaching the site of toxic action,and the toxicity at cell level. When the materials are appliedas sprays to growing plants absorption through the roots, retentionby and penetration into the shoot, transport and localized accumulationare factors which may determine differences in response eitherbetween compounds or between species. The precise assessmentof relative toxicity must therefore involve studies of the effectson whole plants and at cell level. For such assessments it is essential to determine in the firstplace the change in the biological effects brought about bya wide range of dosage. The percentage inhibition of germinationbears a sigmoid relationship to the amount of toxicant in theexternal medium, while the same relationship holds between percentagemortality and the concentration of the spray solution. Accuratecomparisons of relative toxicity can only be obtained when thevariation in reaponse is measured at several dosages and thedata treated by the methods of probit analysis. Using such techniques in germination or spraying experimentsit has been demonstrated that the relative toxicities of chlorinatedphenoxycetic acids, alkyl phenylcarbamates, dinitro-alkylphenols,pentachlorophenol, thioacetic acid, and formamide are greatlydependent on the species. In fact, the order of toxicity maybe reversed from one species to another, while between compoundsthe results of germination tests may or may not be comparablewith those obtained by spray applications. The physical characteristics of the spray solution will in partdetermine the degrees of retention and penetration. For compoundswith a low solubility in water the addition of a hygroscopicsubstance may increase the percentage kill. According to thespecies, spray solutions of a low surface activity may be moreor less toxic than those with a high activity, while the relativeeffects of oil emulsions and aqueous sprays vary between species. For compounds which are freely translocated, the methods ofgrowth analysis are of value for assessing the toxic effects,especially of non-lethal dosages. Since the effects on the growthof the component parts of the plant may be widely divergent,conclusions based on a single criterion are likely to be erroneous.Where movement of the compound is restricted, such as with hydrocarbons,an assessment of toxicity can be obtained by measuring the degreeof localized damage following on the application to the leavesof individual droplets of varying size. Lemna minor has the twin advantages that the experimental conditionscan be controlled and that in some respects its response tophytotoxic compounds is akin to that of unicellular organisms.Since with some compounds at any one dose the depression inthe growth rate remains constant with time (e.g. nitrophenols),while for others the depressant effect is cumulative (e.g. dichloro-phenoxyaceticacid, cupric salts), the nature of the growth response mustfirst be established before comparisons between compounds canbe made. For studies of relative toxicity at cell level two methods haveken employed. The external concentrations in the agar mediumrequired to halve the growth rate of Trichoderma viride havebeen determined, or the dosages required to bring about a standardeffect on the respiration of yeast have been estimated. It is concluded that only by using a range of species and anumber of techniques can relative toxicity be established withprecision.     

Studies in the Principles of Phytotoxicity: II. EXPERIMENTAL DESIGNS AND TECHNIQUES OF STATISTICAL ANALYSIS FOR THE ASSESSMENT OF TOXICITY

Some of the more important statistical methods used in the analysisof experiments concerned with studies of phytotoxicity aredescribed, and are illustrated by data from field and laboratoryexperiments undertaken within the Department of Agricultureof the University of Oxford. Most attention has been given toa consideration of quantal effects, such as the proportionatemortality. Adjustments to allow for natural mortality or theappearance of additional plants during the course of the experimentare outlined, together with the conditions under which the datashould be transformed before analysis. Since the relationshipbetween the proportionate response and some function of thedose or concentration of the toxicant generally follows a normalsigmoid law, the methods of probit analysis are appropriatefor presize estimations. In this connexion, the design of experimetsis discussed and the calculations involved in such an analysisare illustrated. In investigations where quantitative measurements are recorded,the dose-response relationehip may also be of the normal sigmoidform, so that the data be treated by a modification of the probittechnique. The methods of statistical treatment demanded whenthe dose-response relationship does not conform to a normalsigmoid are briefly discussed.     

Studies in the Principles of Phytotoxicity: IV. THE EFFECTS OF THE DEGREE OF NITRATION ON THE TOXICITY OF PHENOL AND OTHER SUBSTITUTED BENZENES

1. The relative toxicity of phenol, o- and p-nitro, 2:4-dinitro-,and 2:4:6- trinitrophenol was measured by up to five techniques.Determinations were made of the concentrations required to reduceby half (i) the growth rate of Trichoderma viride at pH 3, (ii)the frond multiplication rate of Lemna minor at pH 5·1–5·4,(iii) the respiration rate of yeast at pH, (iv) the respirationrate of infiltrated leaf disks of Brassica alba at pH 3, and(v) the number of B. alba seedlings surviving after sprayingwith buffered solutions of the compounds. Whenever possibletoxicity was measured at a pH level below pK so as to eliminatethe effect of pH on toxicity, but in some of the measurementswith 2:4-dinitro- phenol (pK = 4·0) and with picric acid(pK = 0·8) this was not feasible. It was then necessaryto measure toxicity at a pH at which the compound was much dissociated;from the measured values of toxicity of dinitrophenol the toxicityat a lower pH was estimated from the generalized pH-activityrelationship of Simon and Beevers (5952). 2. The relative toxicity of the nitrophenols is very similarwhichever test procedure is employed. The first two nitrationsare accompanied by large increases in toxicity, but with thethird successive nitration there is a decrease. 3. The toxicity of the corresponding mono, di, and trinitroderivatives of anisole, phenetole, toluene, and nitrobenzenewas determined using T. viride. In each series the first andthird stages of nitration brought about large increases in toxicitybut the intermediate one had little effect. 4. All the p-nitro compounds were more toxic than their o- isomers. 5. On the basis of the concepts put forward by Ferguson (1939)and Albert (1951) it is concluded that the toxic action of thenitroanisoles and nitrotoluenes is ‘structurally non-specific’,i.e. the effect is not dependent on the presence or absenceof a particular chemical group in the molecule. With both thenitrobenzene and the phenol series the results suggest thatthe exact chemical structure is an important factor.     

Studies in the Principles of Phytotoxicity: V. INTERRELATIONSHIPS BETWEEN SPECIFIC DIFFERENCES IN SPRAY RETENTION AND SELECTIVE TOXICITY

In a detailed study of the factors which control spray retentionby the shoot, five species with markedly different morphologicalcharacteristics have been examined (Helianthus annuus, Brassicaatha, Linum usitatisrnnwn, Hordeum vulgare, and Pisum sativum).The amount of spray retained, expressed as volume per unit weightof shoot or unit leaf area, is dependent on the stage of developmentof each species, the volume of spray applied, and the surfacetension of the spray solution. The interrelationships betweenthese factors are complex for all the second-order interactionsproved to be highly significant. Under one set of condi tionsthere may be a tenfold difference in retention between two specieswhile under another set the corresponding difference may beas little as twofold. Between a spray output of 14 and 143 ml./m.³ the level of retentionby P. sativum and H. vulgare is linearly related to output butfor H. annuus and B. alba the relationship is curvilinear. Whenthe surface tension is reduced below 40 dynes/cm. retentionby P. sativum and H. vulgare is increased, but for B. alba andH. annuus retention is decreased if the output exceeds 50 ml./m.For a given output, a reduction in the mean droplet size augmentsretention by H. vulgare but not by H. annuus. Differences in retention either between species or between stagesof develop ment are linked with the ratio of leaf area to shootweight, the nature of the leaf surfaces, the angle of incidenceat which the droplets strike the leaf, and localized accumulation.Retention is maximal when the leaf-area ratio is high, the surfacescompletely wetted, and the laminae set in a horizontal plane:once this maximum value is reached any additional spray receivedruns off the shoot. The relationship between retention and the concentration ofthe spray solution required to bring about some standard biologicalresponse has been examined for two groups of compounds—thosewhich are freely translocated (triethanolarnine salts of 2:4-dichloro-,2:4:5-trichloro-, and z-methyl-4-chloro-phenoxyacetic acids)and those which are not (arnrnonium 2:4-dinitro-6-sec-butylphenate).For the first group the equi-effective concentration is inverselyand linearly related to retention since the total amount receivedis of primary importance in determining the inhibition of growth,though the position of the droplets must be taken into account.Placing micro-drops containing the growth regulator on the cotyledonsof L. usitatimmwn inhibits the growth of the shoot less thana spray application of the same amount over the whole shoot:for H. annuus placing the growth regulator on either the firstor second pair of leaves or on the first internode induces moreinhibition of growth than application to the cotyledons. With ammonium dinitro-sec-butylphenate the relationship betweenretention and concentration is also inverse but approximatelylogarithmic for L. usitatisrimum. For some other species thechanges in retention consequent upon a reduction in the surfacetension are not matched by comparable changes in the equi-effectiveconcentration. For B. alba and H. annuus though lowering thesurface tension may decrease retention it may also Himiniahthe concentration because the fall in retention is more thanoffset by a greater penetration of the compound into the shoot. It is concluded that differences in spray retention betweenspecies can play a major role in determining selective actionand the conditions under which this factor may operate mosteffectively are discussed.     

Studies on Foliar Penetration: III. THE EFFECTS OF CHLORINATION ON THE RATE OF PENETRATION OF PHENOXYACETIC ACID AND BENZOIC ACID INTO LEAVES OF PHASEOLUS VULGARIS

A comparative study has been made of the penetration into leafdisks of Phaseolus vulgaris of (a) phenoxyacetic acid and its2-, 4-, 2, 4-, 2, 6-, 3-5, 2, 4, 5-, and 2, 4, 6- chloro derivatives,and (b) benzoic acid and its 2-, 2, 4-, 2, 5-, 2, 3, 6-chloroand 3, 6-dichloro-2-methoxy derivatives. The methods of synthesisof each compound with ¹⁴C incorporated in the carboxyl groupare described. In the series of substituted phenoxyacetic acids it was establishedthat only for 2, 4, 5-T was there an appreciable loss of radioactivityfrom the system either in the light or darkness. In contrast,with the exception of 2, 4-DCBA, ¹⁴C is lost from each memberof the series of substituted benzoic acids. The level and pattern of penetration in the two series is differentiallyaffected by chlorination. In general progressive chlorinationof phenoxyacetic acid leads to an increase in the rate of penetrationin both light and darkness. There are, however, exceptions;for illuminated disks the rate of entry of 2,4,5-T is exceededby 2,4,6-T, 2, 4-D, and 2, 6-D whereas in the dark 2,4,5-T hasby far the highest rate of penetration. Progressive chlorinationof benzoic acid, however, depresses entry in both light anddarkness. Possible relationships between these findings and changes inselected physical properties of each series of compounds havebeen examined. Between members of the series of substitutedphenoxyacetic acids there is little variation in the dissociationconstant whereas for the substituted benzoic acids there isa marked lowering of the pK as the degree of chlorination increases.The rate of elution with chloroform of each compound from abuffered Silocel column gives a measure of the degree of partitioninto a lipid medium at a given pH. At pH 5.2 chlorination ofphenoxyacetic acid results in more rapid elution whereas chlorinationof benzoic acid causes a longer hold up. An apparatus was designed to enable measurements to be madeof the rate at which a compound moves from one aqueous phaseto another through a layer of lipid. Chlorination promotes therate of transfer of phenoxyacetic acid through octanol but retardsthe transfer of benzoic acid. The extent to which chlorinationdepresses the rate of transfer of benzoic acid matches the diminutionin the rate of leaf penetration. For the series of substitutedphenoxyacetic acids transfer rates and penetration rates followsimilar trends in the dark but in the light agreement is lessgood. These findings are discussed in relation to prior studies onthe rate of uptake and the metabolic fate of the ndividual compoundsin a number of plant tissues.     

The Uptake of Growth Substances: VI. A COMPARATIVE STUDY OF THE FACTORS DETERMINING THE PATTERNS OF UPTAKE OF PHENOXYACETIC ACID AND 2,4,5-TRICHOLOROPHEN-OXYACETIC ACID, WEAK AND STRONG AUXINS, BY GOSSYPIUM TISSUES2

Using segments of etiolated hypocotyls of Gossypium, a comparativestudy has been made of the processes which determine the patternsof uptake of a very weak auxin, phenoxyacetic acid (POA), anda very powerful one, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). When segments are placed in solutions of POA-1-¹⁴C, a continuousincrease in the radioactivity of the tissues is accompaniedby the formation of radioactive metabolities which can be separatedfrom POA by techniques of paper chromatography. At the sametime there is a progressive increase in the amount of radio-activitywhich cannot be removed by transferring the tissues to buffer.Uptake is inhibited by low temperature, anaerobiosis, 2,4-dinitrophenol,and iodoacetate. It is concluded that the accumulation of POAinvolves its metabolic conversion to products which do not readilydiffuse out into the external medium. With 2,4,5-T-1-¹⁴C the radioactivity of the segments at firstincreases rapidly but this is followed after two hours by aphase of rapid decrease. No radioactive metoabolites can bedetected by paper chromatography and all of the ¹⁴C taken upcan be rapidly removed by transfer to buffer. The magnitudeof the decrease in radioctivity during the second phase of uptakeis balanced by a release to the medium of a matched amount ofradioactive 2,4,5-T. Uptake of 2,4,5-T is somewhat less sensitiveto temperature and anaerobiosis than uptake of POA and is bycontrast only slightly inhibited by 2,4-dinitrophenol and iodoacetate. Pretreatment of segments in buffer markedly alters the patternof uptake of 2,4,5-T but not that of POA. It reduces both theamount of 2,4,5-T initially taken up and the amount subsequentlyreleased to the medium. In addition, both net loss of radioactivityduring the course of uptake of 2,4,5-T and the reduction inthe extent of uptake following pretreatment are both arrestedby adding streptomycin, but not by the addition of pencillinor chloramphenicol. It is concluded that the uptake of 2,4,5-T involves reversibleaccumulation by a process whose efficiency decreases with time:the most likely systems are a metabolically linked mechanismfor the active transport across a membrane or reversible adsorptionon specific binding sites.     

FACTORS AFFECTING THE TOXICITY OF SEVERAL LICHEN ACIDS: EFFECT OF PH AND LICHEN ACID CONCENTRATION

The effect of pH 5–8 and lichen acid concentration gradients (2.7 times 10⁻² - 2.7 times 10⁻⁶ m ) on the toxicity of the following lichen acids: usnic, lecanoric, evernic, vulpinic, stictic, fumarpro-tocetraric, psoromic, and atranorin, on spores of Funaria hygrometrica was tested. Percent germination and sporeling growth were used as indicators of toxicity. None of the lichen acids were significantly toxic, for either percent germination or sporeling growth at concentrations equal to or below 2.7 times 10⁻⁵ m at pH 7.0, but many of the lichen acids which increased in toxicity at values different from pH 7 may have been toxic at lower concentrations if a different pH was used for the assay. Lichen acid toxicity showed a good correlation with pH for the parameter of spore germination, or sporeling growth, or both. Some lichen acids did not inhibit germination but were effective in retarding sporeling growth, or vice versa. This observation is discussed in relation to changing fatty acids and other lipid composition as germination occurs. Two of the three O-methylated lichen acids (evernic and psoromic) were among the most effective in inhibiting growth over all, but at lower pH values these were less effective than non-O-methylated lichen acids. Stictic, which is also an O-methylated lichen acid, was the least effective inhibitor over all the pH values for both parameters, while vulpinic was the most toxic over all the pH values. The order of relative toxicity for the lichen acids is different, depending on the pH and concentration at which they are tested and depending on the parameter measured. Thus, in an ecological sense, it is difficult to evaluate the adaptive significance of a particular compound or group of compounds without knowing what factors influence the toxicity of those compounds and how these factors vary in the organism's habitat.     

ANTIBIOTIC PROPERTIES OF ACRYLIC ACID, A FACTOR IN THE GASTROINTESTINAL ANTIBIOSIS OF POLAR MARINE ANIMALS.

Sieburth, John McNeill (Virginia Polytechnic Institute, Blacksburg, Va.). Antibiotic properties of acrylic acid, a factor in the gastro-intestinal antibiosis of polar marine animals. J. Bacteriol. 82:72-79. 1961.-Observations were made on acrylic acid to study some of the antibiotic, chemical, and physical properties of this volatile acid which occurs at a concentration of 8% (dry weight) in the marine alga Phaeocystis pouchetii. The sodium salt inhibited both gram-positive and gram-negative bacteria by filter paper disc assays at concentrations of 0.012-12.0 mg/ml. Activity was enhanced by acid reactions approximating those of the avian gut. In an attempt to explain the absence of typical strains of Escherichia coli and the suppression of the atypical coliform microflora in the anterior gastrointestinal segments of pygoscelid penguins in areas where the phytoplankton was dominated by P. pouchetii, chick trials were conducted with sodium acrylate. Acrylate supplementation of chicken feed at levels as low as one-fifth (0.01%) of those estimated to be ingested by penguins under natural conditions, suppressed the E. coli population and permitted its partial replacement by Aerobacter aerogenes. This latter phenomenon was explained by an increase in acrylate resistance by the A. aerogenes population. Acrylate feed levels between 0.01 and 1.0% caused an apparent increase in the growth rate of chicks, whereas 10% levels caused anorexia and death.     

INVESTIGATIONS ON FUNGICIDES. III. THE FUNGITOXICITY OF 3- AND 5-ALKYL-SALICYLANILIDES AND PARA-CHLOROANILIDES

The anilides and para -chloroanilides have been prepared from the first four homologues of the 3- and 5-alkylsalicylic acid series and the fungistatic activity of these compounds has been assessed by two methods. In tests against mycelium, the chloroanilides usually induced less retardation of growth than the corresponding anilides. The effect of introducing an alkyl grouping was in general to reduce the fungistatic effect but with the n -propyl derivatives this trend was less marked. Salicylanilide gave the greatest over-all inhibition of the fungi investigated.     

糖类和pH值的改变对十二碳二元酸发酵的影响

烷烃发酵是非均相发酵,其发酵液中存在气相、固相、水相和油相。因此,烷烃发酵与一般微生物发酵方法不一样。它是高耗氧、高产热的发酵过程,并且会在发酵过程中产生乳化剂,以便油相和水相混匀,使微生物更好地利用烷烃[1～3]。烷烃和糖类等水溶性基质不同:烷烃的疏水性决定…     

The Uptake of Growth Substances: II. THE ABSORPTION AND ACCUMULATION OF 2:3:5-TRIIODOBENZOIC ACID BY THE ROOT AND FROND OF LEMNA MINOR

The absorption by Lemna minor of 2 : 3 : 5-triiodobenzoic acid(TIBA), labelled in the 2 position with iodine-131, has beeninvestigated. Under constant conditions of light (300 foot candles)and temperature (25?C.) the course of uptake by the whole plantis dependent on the concentration of TIBA in the culture solution(pH 5.I). Up to circa 1 mg./l. a high rate of uptake in thefirst 30 minutes is followed by a slower but steady accumulationduring the next 4.5 hours. When the concentration is increasedto 5 mg./1. uptake, at first rapid, falls off progressivelyso that after 1-2 hours the content of the tissues starts todecrease because TIBA moves out in to the external solutionfaster than it enters. The magnitude of this reversal from apositive to a negative rate of uptake,.partitularly for theroots, is even more pronounced at 10 mg/l. When plants, first placed in labelled solutions for 2 to 2.5hours are transferred to culture solution the loss of the labelledcompound to the external solution, especially from the roots,is very rapid : the decrease in root content may reach 90 percent. in the first 80 minutes. The initial rate of egress islittle affected either by the hydrogen ion concentration orthe presence of unlabelled TIBA in the external solution. Between5, 15, and 25? C. the temperature quotients range from 1.29to 1.70 for the root and 1.66-1.37 for the frond. Comparable experiments on the initial phase of uptake duringthe first 2o to 30 minutes demonstrate that (a) the rates aregreatly dependent on the external pH i.e. uptake is largelyin the molecular form and (b) between 5 and 15?C. the ratesare not temperature dependent but between 15 and 25?C. theyare: the quotients for roots and frond are 2.6 and 2.0. Comparisons of the course of uptake of normal plants and plantspreviously frozen in liquid air showed that at both I? and 25?C.'pre-frozen' fronds continue to accumulate TIBA and may containat the end of 5 hours 8 times as much as control fronds. Incontrast, the uptake by the pre-frozen roots is depressed. Theaddition of high (30-50 mg./l.) but not low (10 mg./1.) concentrationsof indole-3-acetic acid (IAA) to the external solution alsocauses a striking accumulation of TIBA in the frond but uptakeby the roots is not changed. Lastly, the presence of TIBA in the external solution whilenot affecting the uptake of cerium-144. in the first 2 hourssubsequently depresses uptake by the root but not by the frond. These findings are compared with the similar pattern of uptakefor z,4-dichlorophenoxyacetic acid described in the previouspaper. The nature of the processes controlling the inward andoutward flow of TIBA, their location within the cell and theirbearing on the physiological actions of auxins are discussed.     

Studies on Extension Growth in Coleptile Sections: III. THE INTERACTION OF TEMPERATURE AND {beta}-INDOLYLACETIC ACID ON SECTION GROWTH

Wheat coleoptile sections were grown at various temperaturesfrom 1–40°C. in water and solutions of the sodiumsalt of ß-indolylacetic acid (NaIAA) ranging fromlow to very high concentrations (0.001 p.p.m. to 10,000 p.p.m.). Growth-time curves are sigmoid, obviously so under conditionsunfavourable to growth, less clearly as conditions either oftemperature or growth-substance supply are improved, the pointof inflection moving nearer to zero time. The growth-rate isreduced by temperatures below the optimum, and although growthcontinues for a longer time, final section length is also reduced.Such reductions are also brought about by sub-optimal levelsof NaIAA and by supra-optimal levels of both factors. In the test method employed, sections are grown in closed tubesof small volume, and after a time lose turgidity and becomewaterlogged; the onset of this condition is accelerated by hightemperature or growth-substance concentration, and greatly delayedby low temperature. Under comparable conditions, but with thetubes uncorked, flaccidity is delayed even at high temperatureor high concentration of NaIAA. If sections are transferred from one temperature to anotherthe change in growth-rate is abrupt; effects of transfer onfinal length are complex. A contour diagram represents the idealized relationships betweensection growth and temperature and NaIAA supply over their wholerange of effectiveness. Relations between temperature and growthin other systems are briefly discussed.     

粪产碱菌的Tn5转座诱变及吲哚乙酸生物合成特性的研究

粪产碱菌(Alcaligenes faecalis)A1501的吲哚乙酸(IAA)合成需要外源色氨酸参与。在不含色氨酸的限制性培养基中,A1501能良好生长,但不能合成IAA,表明在A1501中存在一条依赖于色氨酸的IAA合成途径。A1501的IAA合成具有菌体密度依赖特性。采用Tn5转座诱变技术构建A1501的突变库,从3500多株Tn5转染子中分离到一株色氨酸营养缺陷型突变株AT63。该Tn5突变株在不含色氨酸的限制性培养基上不能生长,但仍能进行IAA的生物合成,每毫升菌体密度等于10的突变株菌体的IAA合成量为224μg。对突变株AT63的研究表明在A1501中至少存在两条IAA合成途径：一条以色氨酸为合成前体,另一条以吲哚-3-磷酸甘油为前体。Southern杂交结果表明突变株中Tn5插入位点可能位于编码色氨酸合成酶基因上。     

核酸起始序列、终止序列和插入序列的统计分析

对八百个核酸序列进行了统计分析,讨论了起始序列、终止序列、插入序列、间隙序列以及序列的氨基酸编码区的各项信息指标,进行了相互比较,并讨论了这些指标和分子进化的统计相关性.     

The Uptake of Growth Substances: III. INFLUENCE OF INDOLEACETIC ACID AND OTHER AUXINS ON THE UPTAKE OF 2,4-DICHLOROPHENOXY-ACETIC ACID BY CHLORELLA

When 2,4-dichlorophenoxyacetic acid, labelled with ¹⁴C, is accumulatedby Chlorella pyrenoidosa, an appreciable fraction, which increaseswith time, is held within the cell in a form which is not removedwhen the cells are placed in a solution containing the unlabelledcompound. The accumulation of this fraction is dependent uponthe supply of metabolic energy since it is affected by temperature,light, and the addition of inhibitors or citrate to the externalmedium. The uptake of this metabolically accumulated 2,4-D follows apattern which indicates that a single enzymic reaction is apredominant component of the uptake process. In the presenceof the other auxins, including indoleacetic acid, 2,4,5-trichlorophenoxyaceticacid and 4-chlorophenoxyacetic acid, the uptake of 2,4-D isdepressed and the changes suggest that there is competitionat the site of this reaction. The nature of the competitionis seemingly of the type where each compound serves as a substratefor the enzyme. It may be significant that the extent to which the individualauxins compete with 2,4-D is in the same order as their generaleffectiveness as growth regulators for other species.     

Phase Change in Hedera helix L.: III. THE EFFECTS OF GIBBERELLINS, ABSCISIC ACID AND GROWTH RETARDANTS ON JUVENILE AND ADULT IVY

Gibberellic acid, applied to delaminated petioles of rootedcuttings of juvenile and adult ivy initially induced internodeelongation and abnormal leaf development, and suppressed apicaldominance. Juvenile cuttings were affected only transientlyand soon reverted to normal growth. Adult cuttings, insteadof resuming normal growth after this initial response to GA₃,gradually developed many juvenile characteristics. Approximately16 weeks after treatment at 25 ?C nearly all shoots of adultcuttings had undergone complete rejuvenation. Lower temperaturereduced the speed of response to GA₃. A mixture of gibberellinsA₄ and A₇ had effects similar to those of GA₃ on the growthof juvenile and adult cuttings. Treatment of both phases ofivy with abscisic acid (ABA) induced no visible effects andwhen ABA was applied with GA₃ it did not reduce the responseof either phase to the gibberellin. CCC had a marked dwarfingeffect on juvenile ivy but did not induce pre-maturation. However,extraction of gibberellin-like substances from severely dwarfedplants suggested that CCC was not exerting its growth retardingeffect through an inhibition of gibberellin biosynthesis. AMO1618 did not retard growth of juvenile ivy cuttings.     

AMPHOTERIC COLLOIDS : III. CHEMICAL BASIS OF THE INFLUENCE OF ACID UPON THE PHYSICAL PROPERTIES OF GELATIN.

1. The method of removing the excess of hydrobromic acid after it has had a chance to react chemically with gelatin has permitted us to measure the amount of Br in combination with the gelatin. It is shown that the curves representing the amount of bromine bound by the gelatin are approximately parallel with the curves for the osmotic pressure, the viscosity, and swelling of the gelatin solution. This proves that the curves for osmotic pressure are an unequivocal function of the number of gelatin bromide molecules formed under the influence of the acid. The cc. of 0.01 N Br in combination with 0.25 gm, of gelatin we call the bromine number. 2. The explanation of this influence of the acid on the physical properties of gelatin is based on the fact that gelatin is an amphoteric electrolyte, which at its isoelectric point is but sparingly soluble in water, while its transformation into a salt with a univalent anion like gelatin Br makes it soluble. The curve for the bromine number thus becomes at the same time the numerical expression for the number of gelatin molecules rendered soluble, and hence the curve for osmotic pressure must of necessity be parallel to the curve for the bromine number. 3. Volumetric analysis shows that gelatin treated previously with HBr is free from Br at the isoelectric point as well as on the more alkaline side from the isoelectric point (pH ≧ 4.7) of gelatin. This is in harmony with the fact that gelatin (like any other amphoteric electrolyte) can dissociate on the alkaline side of its isoelectric point only as an anion. On the more acid side from the isoelectric point gelatin is found to be in combination with Br and the Br number rises with the pH. 4. When we titrate gelatin, treated previously with HBr but possessing a pH = 4,7, with NaOH we find that 25 cc. of a 1 per cent solution of isoelectric gelatin require about 5.25 to 5.5 cc. of 0.01 N NaOH for neutralization (with phenolphthalein as an indicator). This value which was found invariably is therefore a constant which we designate as "NaOH (isoelectric)." When we titrate 0.25 gm. of gelatin previously treated with HBr but possessing a pH < 4.7 more than 5.5 cc. of 0.01 N NaOH are required for neutralization. We will designate this value of NaOH as "(NaOH)_n," where n represents the value of pH. If we designate the bromine number for the same pH as "Br_n" then we can show that the following equation is generally true: (NaOH)_n = NaOH (isoelectric) + Br_n. In other words, titration with NaOH of gelatin (previously treated with HBr) and being on the acid side of its isoelectric point results in the neutralization of the pure gelatin (NaOH isoelectric) with NaOH and besides in the neutralization of the HBr in combination with the gelatin. This HBr is set free as soon as through the addition of the NaOH the pH of the gelatin solution becomes equal to 4.7. 5. A comparison between the pH values and the bromine numbers found shows that over 90 per cent of the bromine or HBr found was in our experiments in combination with the gelatin.     

HOMOVANILLIC ACID AND 5-HYDROXYINDOLEACETIC ACID IN THE CEREBROSPINAL FLUID OF PATIENTS WITH SENILE DEMENTIA, PRESENILE DEMENTIA AND PARKINSONISM

Abstract— Four groups, one of healthy volunteers, one of senile dementia, one of presenile dementia, and one of patients with parkinsonism were compared according to the values of HVA and 5-HIAA in CSF. The levels of HVA and 5-HIAA were highest in the group of healthy volunteers and decreased in the following order: senile dementia, presenile dementia, and parkinsonism. In the groups the two metabolites were positively correlated. These results are in agreement with earlier investigations showing disturbances of monoamine metabolism in the brain of patients suffering from these syndromes.     

COMBINED EFFECT OF 6-BENZYLAMINOPURINE,GIBBERELLIC ACID,AND 3-INDOLEACETIC ACID ON THE EXPANSION OF ISOLATED PUMPKIN COTYLEDONS

The effect of 6-benzylaminopurine, gibberellin, and 3-indoleacetic acid, used separately or in combinations, on the expansion of isolated pumpkin cotyledons has been studied. All three types of phytohormones can promote the expansion of isolated cotyledons. The resulting effect depends on the concentration of the particular phytohormone and on its quantitative ratio with the other phytohormones. The optimum combinations of phytohormones introduced externally varied according to the seed. The stimulating effect on the expansion of cotyledons is evidently exerted by those phytohormones which are present in the seeds in minimum amounts. An analysis of the concentration curves of the phytohormone effect indicates that they are not interchangeable as regards their influence on the expansion of isolated pumpkin cotyledons.