Studies on Plant Growth Hormones: I. BIOLOGICAL ACTIVITIES OF 3-INDOLYLACETALDEHYDE AND 3-INDOLYLACETONITRILE

1. Two neutral plant hormones, one isolated recently from plants(3-indolylacetonitrile) and the other (3-indolylacetaldehyde)reported to be present in plants, are avaible as pure syntheticcompounds for investigation of their biological activities.This paper is mainly concerned with their effects on cellelongationin the Avena coleoptile
2. 3-Indolylacetaldehyde is considerablyless active than 3-indolylaceticacid in the Avena straight-growthtest; for example, a 1.0 mg./l.solution of the aldehyde showsan activity equivalent to thatof a 0.1 mg./l. solution of theacid
3. An acidic substance is produced in solutions of the aldehydeduring the period of assay. In some experiments it accountsfor all of the activity shown by the aldehyde solutions, onthe assumption that it is 3-indoylacetic acid, and in otherexperiments it shows a greater activity than that of the aldehydesolutions from which it was obtained. Therefore, it is concludedthat 3-indolylacetaldehyde, itself is either inactive or inhibitory.Acid production in aldehyde solutions in vitro is much lower,a fact which suggests that there is enzymatic oxidation of aldehydeto acid in the presence of coleoptiles.
4. The activities of3-indolylacetaldehyde in the pea test andin root-inhibitionand of 3-indolylacetone in the straight-growthtest are brieflyreported.
5. 3-Indolylacetonitrile is considerably more activethan 3-indolylaceaticacid in the Avena straight-growth test;for erample, a 0.1 mg./l.solution of the nitrile shows an activityequivalent to a 1.0mg./l. solution of the acid. The inhibitoryeffect at concentrationsabove 1.0–10.0 mg./l. is lesswith the nitrile than withthe acid.
6. There is negligible productionof acid in solutions of the nitrileboth in vitro and in thepresence of Avena coleoptiles at temperaturesranging from –18?to 25? C. for varying lengths of time.The possibility of enzymaticconvesion of nitrile to acid insidethe cells of the coleoptileis discussed
7. The activities of 3-indolylacetamide and of 2:4-dichlorophenoxyaceticacid and the corresponding nitrile are considered in this connexion
8. The nitrile is destroyed by treatment with alkali but notbyacid. In the light of these results, it is desirable to re-examineprevious work on identification of auxins in plants by theiracid and alkali sensitivity. Evidence for the existence of thenitrile in a number of other plants is presented.

     

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.     

A study of the effects of fungitoxic compounds on Phytophthora cinnamomi in water

Copper and chlorine-releasing compounds were the most fungitoxic of 13 compounds tested in water for inhibition of Phytophthora cinnamomi. Mycelium was killed when immersed for 24 h in suspensions containing copper (13–45 mg/1) or a solution containing free residual chlorine (100 mg/1). Sub-lethal concentrations of these compounds reduced the numbers of sporangia. Exposing zoospores of P. cinnamomi for 60 s to water containing 2 mg free residual chlorine/1 reduced subsequent colony production on agar plates by 96–100%.
Prothiocarb, etridiazole ex. and furalaxyl killed mycelium immersed in solutions or suspensions for 3–6 days at 1500, 1000 and 600 mg a.i./l respectively and suppressed sporangium production at 1000, 500 and 300 mg/1.
Mycelium survived 3 days' immersion in ethyl hydrogen phosphonate compounds at 4000 mg a.i./l but 1000 mg a.i./l suppressed sporangium formation.
1-(2-Cyano-2-methoxyiminoacetyl)-3-ethyl urea and drazoxolon did not kill mycelium at 2000 and 1500 mg a.i./l respectively with a 6-day exposure, but reduced numbers of sporangia produced.     

Some effects of differently-acting nematicides on the cereal cyst-nematode (Heterodera avenae) and on the appearance of ''scorch'' in spring wheat on light loamy sand

In fungitoxicity tests against Phytophthora cinnamomi on Chamaecyparis lawsoniana cv. Ellwoodii, a drench of furalaxyl (1000 mg a.i./l) applied to the compost in which 1-yr-old plants were growing, 1 wk before they were inoculated with 650 000 zoospores, controlled disease for at least 12 months. With an inoculum dose of 650 zoospores/plant, furalaxyl at 500 mg a.i./l controlled disease even when inoculation was 12 wk after fungicide treatment. Aluminium tris (ethyl phosphonate) (2000 mg a.i./l) applied as a drench 1 wk before inoculation with 650 000 zoospores/plant did not prevent root infection but delayed foliar symptoms for 9 months: the same treatment, using etridiazole (500 mg a.i./l) only slightly reduced disease incidence. When applied as a single drench 2 days before inoculation, prothiocarb (2000 mg a.i./l) and cuprammonium compounds (200 mg a.i./l) were much less effective than furalaxyl (1200 mg a.i./l), sodium ethyl phosphonate (1500 mg a.i./l), aluminium tris (ethyl phosphonate) (1500 mg a.i./l) or etridiazole (500 mg a.i./l). However, a drench of furalaxyl at 1000 mg a.i./l, aluminium tris (ethyl phosphonate) at 2000 mg a.i./l or etridiazole at 500 mg'a.i./l did not eradicate P. cinnamomi from compost containing infected root debris. Pre-planting drenching of the compost was ineffective. All fungicide treatments were non-phototoxic to 1-yr-old C. lawsoniana cv. Ellwoodii. These results are of special relevance to the control of P. cinnamomi on container-grown woody ornamentals.     

Ion Exchange in Sphagnum and its Relation to Bog Ecology

In Sphagnum cuspidatum unesterified polyuronic acids form 12per cent. of the dry weight; in S. acutifolium 25 per cent,of the dry weight. A good correlation has been found for Sphagnabetween the content of unesterified polyuronic acid and thecation exchange ability, and between cation exchange abilityand height of normal habitat above the water table. Anion exchangeability in Sphagna is less than 0.0026 m.eq./g. D.W. comparedwith about 1.2 m.eq./g. D.W. for cations at pH values above7. In natural conditions the exchange sites are, however, onlypartly dissociated. The production of new plant material ina bog dependent on rainwater for nutrients can be sufficientto maintain the pH below 4.5, but on average in England onlyof the order of 2 per cent, of the monovalent cations otherthan H⁺ could be retained in exchangeable form. A greater proportionof polyvalent cations could be retained. The kinetics of cation exchange are consistent with a heterogeneousexchange phase containing regions of high charge density andregions with lower charge density. At equilibrium the proportionsof different cations in the exchange phase are largely explicableby a Donnan distribution, but there are notable exceptions.Two estimates based on Donnan distribution suggest that withlow external pH and/or low cation concentration the apparentconcentration of exchange sites may be 2-3 eq./l., falling withrise in pH and/or increase in cation concentration to 0-9-1-5 eq./l. The apparent dissociation coefficient also variesin these conditions from 2 x 10^–2 to 1 x 10^–4.     

The Effects of Indole-3-Acetic Acid and 2:4-Dichlorophenoxyacetic Acid on the Growth Rate and Endogenous Rhythm of Intact AvenaColeoptiles

The rates of elongation of the coleoptiles of Avena seedlings,subjected to intermittent immersion in solutions of IAA or 2:4-Dfor various total periods, were determined from measurementsof photographs taken every hour by infra-red radiation. Immersion in 17·5 mg./l. IAA for 1–5 hours causeda large increase in the growth rate followed by a depression.When the seedlings were immersed in 8·75 mg./l. IAA forperiods of 12 or 24 hours the depression was partially overcomeso long as the treatment was continued. Absorption of additionalIAA by the coleoptiles reduced their geotropic sensitivity. Penetration of 2:4-D (sodium salt) into the coleoptiles wasslower than that of IAA and the resulting stimulation of thegrowth rate was less, particularly in unbuffered solutions.After the treatment the growth rate declined slowly to aboutthe normal value. Results with coleoptiles were very similar to those previouslyobtained with rhizomes of Aegopodium and suggest that inhibitionof growth following stimulation by IAA may be of general occurrence.Possible causes of the inhibition are discussed and a comparisonis made between the results with intact coleoptiles and observationsmade by others on coleoptile sections. Temporary immersion of the seedlings in auxin solutions depressedthe rate of elongation of the primary leaf while it increasedthat of the coleoptile. It caused little disturbance of theendogenous rhythm induced by change from light to darkness.The suggestion that such rhythms can be explained in terms ofvariation in concentration of IAA-oxidase is not supported.     

Low Temperature Treatments Induce an Increase in the Relative Content of Both Linolenic and {lambda}3-Hexadecenoic Acids in Thylakoid Membrane Phosphatidylglycerol of Squash Cotyledons

The effect of low temperatures on the fatty acid compositionof phosphatidylglycerol (PG) in thylakoid membranes, in particularon the ratios of nmol% 16:1(3t) (mg fresh weight)^–1 ofcotyledons and nmol 16:1(3t) (mg chlo rophyll)^–1 weremeasured during squash seedling growth. Plants were germinatedand grown for one day at 30°C then were either kept at 30°C(control plants) or trans ferred to low temperatures (18, 14or 10°C). When plant were transferred from 30°C to lowtemperatures, the increase in fresh weight was gradually limited.The lowe the temperature, the smaller was the fresh weight.In contrast, the relative content of 16:1(3t) and 18:3, as wella the ratios of nmol 16:1(3t) (mg chlorophyll)^–1 and mol%16:1(3t) (mg cotyledon fresh weight)^–1 increased indicatingthat the increase of fresh weight and chlorophyll was mor sensitiveto low temperature than PG desaturation in thyla-koid membranes.Furthermore, low temperatures inducei an increase in 16:1(3t)and 18:3 (the final products of PC synthesis) at the expenseof 16:0 and 18:1 (the initial products of PG synthesis). However,within a range of temperature from 10 to 18°C, the extentof these changes (nmol% of 18:3 or 16:1(3t) per day) was graduallylimited by lower temperatures. We therefore propose that lowtemperature inhibit both fatty acid synthesis and desaturationactivities. However, at low temperatures the fatty acid synthesisis likely to be more strongly inhibited than the desaturationactivities, thus explaining the observed increase in the relativecontent of PG-18:3 and PG-16:l(3t). Results an discussed interms of the mechanism which could be in volved in the metabolismof PG in squash cotyledons. (Received July 5, 1996; Accepted March 10, 1997)     

The effects of temperature and the Rht3 dwarfing gene on growth, cell extension, and gibberellin content and responsiveness in the wheat leaf

The effects of low temperature and the Rht3 dwarfing gene onthe dynamics of cell extension in leaf 2 of wheat were examinedin relation to gibberellin (GA) content and GA-responsivenessof the extension zone. Leaf 2 of wild-type (rht3) wheat closelyresembled that of the Rht3 dwarf mutant when seedlings weregrown at 10C. The maximum relative elemental growth rate (REGR)within the extension zone in both genotypes was lower at 10Cthan at 20C, but the position with respect to the leaf basewas unaffected by temperature. The size of the extension zoneand epidermal cell lengths were similar in both genotypes at10C. Growth at 20C, instead of 10C, increased the lengthof the extension zone beyond the point of maximum REGR in thewild type, but not in the Rht3 mutant. Increasing temperatureresulted in longer epidermal cells in the wild type. Treatingwild-type plants at 10C with gibberellic acid (GA₃) also increasedthe length of the extension zone, but the Rht3 mutant was GA-non-responsive.However, the concentrations of endogenous GA₁ and GA₃ remainedsimilar across the extension zone of wild-type plants grownat both temperatures, despite large differences in leaf growthrates. The period of accelerating REGR as cells enter the extensionzone, and the maximum REGR attained, are apparently not affectedby GA. It is proposed that GA functions as a stimulus for continuedcell extension by preventing cell maturation in the region beyondmaximum REGR and that low temperature increases the sensitivitythreshold for GA action. Key words: Cell extension, gibberellin, Rht3 dwarfing gene, temperature, wheat leaf     

The effects of varying the cellular and extracellular concentrations of sodium and potassium ions on the uptake of glycine by mouse ascites-tumour cells in the presence and absence of sodium cyanide

1. Tumour cells were starved to deplete them of ATP and transferred to 0.9mm-glycine in Ringer solutions containing 2mm-sodium cyanide and various Na(+) and K(+) concentrations. The uptake of glycine then usually reached a peak by about 10min. 2. When cellular [Na(+)] and extracellular [Na(+)] were each about 30m-equiv./l., the maximum amount of glycine absorbed increased between 1.2- and 3.0-fold on lowering extracellular [K(+)] from 128 to 10m-equiv./l. 3. When extracellular [Na(+)] was 150m-equiv./l., the ratio, R, of the cellular to extracellular glycine concentrations increased progressively, from near 1 to about 9, when cellular [Na(+)] was lowered from 120 to 40m-equiv./l. 4. When cellular [Na(+)] was almost constant, either at 45 or 70m-equiv./l., R fell about 14-fold when extracellular [Na(+)] varied from 150 to 16m-equiv./l. 5. Values of R near 0.2 were found when cellular [Na(+)] was about four times as large as extracellular [Na(+)]. 6. R fell about threefold when the cells were put with 12mm- instead of 0.9mm-glycine. 7. The results were taken to imply that, under these conditions, the spontaneous movements of both Na(+) and K(+) across the cell membrane, down their respective concentration gradients, served to concentrate the glycine in the tumour cells (Christensen's hypothesis).     

Studies on the Growth in Culture of Plant Cells: VII. EFFECTS OF KINETIN ON THE CARBOHYDRATE AND NITROGEN METABOLISM OF ACER PSEUDOPLATANUS, L CELLS GROWN IN SUSPENSION CULTURE

Aspects of the carbohydrate and nitrogen metabolism of Acerpseudcplatanus, L cell suspension cultures grown on a syntheticmedium containing 2 per cent glucose and 1.0 mg/l 2,4-dichlorophenoxyaceticacid and kinetin either at 0.25 mg/l (low kinetin) or at 2.5mg/l (high kinetin) are described. High kinetin inhibits growthas measured by increase in cell number, packed-cell volume,and cell dry weight. Although not inhibitory to glucose utdization,high kinetin inhibits the O₂ uptake of the cells. Such cellscontain only a trace amount of fructose and their rate of O₂uptake can be raised to that of the low kinetin cells by a periodof fructose feeding. The O₂ uptake of both kinds of cell issensitive to malonate but the stimulation of O₂ uptake inducedby bis(hexafiuoroacetonyl)-acetone (‘1799’) at 0.2mM is much less with the high-kinetin than the low-kinetin cells.The enzymes phosphoglucoseiseomerase and glucose-6-phosphatedehydrogenase are much less active in the high-kinetin cells.Mitochondria isolated from both kinds of cells show good respiratorycontrol although slightly lower values for Q_O2(N), ADP/O ratioand control ratio are recorded with mitochondria from the highkinetin cells. Kinetin at 2.5 mg/l slightly reduces the ADP/Oratio of isolated mitochondria but at 4.0 mg/l their responseto ADP is completely suppressed. Extracellular hemicelluloseformed in presence of high kinetin has a reduced content ofgalactose and xylose and an increased content of glucose. Theseobservations indicate that the inhibition of respiration byhigh kinetin is mainly due to suppression of glucose conversionto other sugars rather than to inhibition of glycolysis or terminalrespiration. High kinetin decreases the rate of protein but not of amino-acidsynthesis. Suppression of the synthesis of particular proteinsmay be an important factor responsible for the reduced cellyield of the cultures in presence of high kinetin. The significanceof these observations to our understanding of the critical metaboliceffects of cytokinina is discussed. Acer pseudoplatanus cells release amino acids into their culturemedium early in the period of batch culture and largely reabsorbthem as incubation proceeds.     

Studies on Foliar Penetration: I. FACTORS CONTROLLING THE ENTRY OF 2, 4 - DICHLOROPHENOXYACETIC ACID

A technique, using leaf disks, has been developed to study thepenetration of isotopically labelled compounds into leaves underconditions where there is no appreciable change in the concentrationof the external solution and no subsequent translocation. Inthis preliminary survey, the leaves of Phaseolus vulgaris andColeus Blumei were employed to investigate the entry of 2,4-dichlorophenoxyaceticacid (2,4-D), labelled in the carboxyl group with ¹⁴C. Over3 days there is no loss of ¹⁴C to the atmosphere from treatedleaves of Phaseolus. The rate of penetration is enhanced when(a) the leaves are young, (b) the water status is lowered, (c)the temperature is raised (Q₁₀=2.3–2.8), and (d) a surface-activeagent is added to the external solution. Penetration is alsofavoured by a decrease in the pH, the relation indicating thatboth ions and molecules enter. Penetration is greater in thelight and prior illumination of the tissues positively affectsthe subsequent rate in the light, but not in the dark. In boththe light and the dark considerably more 2,4-D penetrates theabaxial surface of Phaseolus leaves. For Coleus an even greaterdifference between surfaces is found in the light but not inthe dark. For both species in the light the rates of entry intoboth surfaces are proportional to their respective stomataldensities. The simultaneous addition of indoleacetic acid tothe external solution caused more 2,4-D to enter Phaseolus leaves,but the addition of triiodobenzoic acid restricts entry. Therate of penetration remains constant over 24 hours and between0.1 and 200 mg./l. the rate is linearly related to concentration.Subsequent to entry, the 2,4-D is in a form which does not diffusefrom the tissue into buffer or exchange with unlabelled 2,4-D.Moreover, no outward movement takes place from treated tissuewhich has been frozen and thawed. These findings are discussedin relation to previous work on foliar penetration. It is concludedthat at least with Phaseolus penetration largely takes placethrough the guard cells and/or accessory cells.     

Toxicity of diflubenzuron, pyriproxyfen, imidacloprid and diafenthiuron to the predatory bugOrius laevigatus (Het.: Anthocoridae)

The susceptibility of the predatory bugOrius laevigatus (Fieber) to the insect growth regulators diflubenzuron, pyriproxyfen, the nitroguanidine insecticide imidacloprid and the thiourea compound diafenthiuron was investigated in the laboratory. Fifth-instar nymphs were exposed to formulated materials of each compound and adults were exposed to formulated materials of diafenthiuron and imidacloprid. In each case, exposure via ingestion and residual contact was tested. Pyriproxyfen was harmless toO. laevigatus nymphs by both ways of exposure. The respective LC₅₀-values of diflubenzuron via ingestion and residual contact were 229.9 and 391.1 mg a.i./l. Diafenthiuron did not cause significant mortality to fifth-instar nymphs and adults via ingestion but was toxic by residual contact with LC₅₀-values of 329.4 mg a.i./l and 125.9 mg a.i./l for nymphs and adults respectively. Imidacloprid proved to be the most toxic compound with LC₅₀-values of 1.1 and 0.04 mg a.i./l for nymphs and 2.1 and 0.3 mg a.i./l for adults, via ingestion and residual contact, respectively. The results suggest that use of pyriproxyfen in an integrated pest management programme will not cause any problems but that imidacloprid, and to a lesser extent, also diflubenzuron and diafenthiuron could be harmful to the predator.     

The Uptake of Growth Substances: I. FACTORS CONTROLLING THE UPTAKE OF PHENOXYACETIC ACIEDS BY LEMNA MINOR

An analysis has been made of the factors controlling the uptakeof 2:4-dichloro-phenoxyacetic acid (2:4-D) and related compoundsby Lemna minor, grown under controlled conditions. All compoundswere labelled with ¹⁴C in the carboxyl group and the ¹⁴C inthe plants, after liquid combustion, assayed as barium carbonate. With 2:4-D the rate of entry from concentrations of 8 to 32mg./l. is maximal in the first 20 minutes, then falls progressivelyuntil the rate is zero between 1 and 2 hours and in the thirdphase (up to 24 hours) there is a net loss from the plants dueto an outward movement of the compound back into the externalsolution. When the chlorine substitutions are in the 2:6-positionthe course of uptake is similar, save that loss to the solutiontakes place later. For the 2-chloro-substitution, after theinitial phase of uptake there is some loss but this is followedby a period of recovery and uptake again proceeds, but slowly.In contrast, the course of uptake over 24 hours of phenoxyaceticacid is normal, i.e. there is a steady accumulation. When plants are pretreated with labelled 2:4-D for 30–60minutes and transferred to water or culture solution then over90 per cent. of the ¹⁴C is found in the external medium after4:5 hours and this release cannot be accounted for in termsof exchange processes since the addition of unlabelled compoundto the medium retards the rate of loss. This loss is slowedbut not stopped at 1.25°C. and up to 22.5°C. the rangeof the Q₁₀ is 1.6–1.9. Uptake in the first 30 minutes is temperature sensitive between7.5 and 30°C. (Q₁₀ 2.3–2.6) and in general is positivelyand curvilinearly related to the external concentration. Pretreatmentwith unlabelled compound up to 2 hours progressively depressesthe subsequent initial uptake of labeled growth regulator. Itis concluded that initially the rate of entry greatly exceedsthe rate of loss but that with time the ratio steadily diminishesto less than unity. Initial uptake of 2:4-D is markedly dependent on the pH of thesolution and closely but not completely correlated with theexternal concentration of undissociated molecules. On the otherhand, the outward movement is relatively unaffected by the externalpH. Combinations of concentration and time of exposure which bringabout loss to the solution need not cause any permanent retardationof growth. In fact, exposure for 1 hour to 8 mg./l. significantlyaccelerated growth in the next 8 days. These results are discussed in relation to previous findingsand it is concluded that the pattern of uptake is determinedon the one hand by the chemical structure of the growth substanceand on the other by specific physiological differences at celllevel.     

The Effects of Externally Applied 3-indolylacetic Acid on Phototropic Induction and Response in the Coleoptile of Avena

The effects of intermittent immersion of Avena seedlings insolutions of IAA on the response of the coleoptiles to unilateralillumination in the region of that producing the second positivecurvature were studied by means of automatic time-lapse photographywhich enabled the growth-rate and curvature to be recorded simultaneously. Phototropic induction occurred even after the coleoptiles hadabsorbed sufficient IAA from a 10^-4 M. solution to raise theirrate of elongation to about twice the normal value. Phototropiccurvature, which had been temporarily inhibited by a curvaturein the opposite direction induced by the IAA, became evidentas soon as this curvature had ceased to operate. In coleoptiles, supplied with IAA after the commencement ofa phototropic curvature, the response was temporarily suppressed.It was resumed as soon as the effects of the exogenous IAA haddisappeared. The ability of the coleoptiles to produce a slight phototropicresponse persisted even when their growth-rate had been greatlyreduced by previous removal of the endosperm. Increasing thegrowth-rate by supplying the starved seedlings with IAA or sucrose,separately or together, failed to increase the response. Decapitation did not prevent phototropic induction, but delayedthe onset of the response. Application of IAA by intermittentimmersion in a 0.1 mg./l. solution, after the decapitated coleoptileshad been exposed to unilateral illumination, increased the rateof growth but reduced the response. The results suggest that in these experiments phototropic inductionwas not mediated by any direct action of light on the displacement,inactivation, or rate of synthesis of an endogenous auxin. Theyare in agreement with the hypothesis that the stimulus causedan asymmetrical distribution of a co-factor of auxin.     

Zinc status affects p53, gadd45, and c-fos expression and caspase-3 activity in human bronchial epithelial cells

This study was designed to examine theinfluence of zinc depletion and supplementation on the expression ofp53 gene, target genes of p53, andcaspase-3 activity in normal human bronchial epithelial (NHBE) cells. Aserum-free, low-zinc medium containing 0.4 µmol/l of zinc [zincdeficient (ZD)] was used to deplete cellular zinc over one passage. Inaddition, cells were cultured for one passage in media containing 4.0 µmol/l of zinc [zinc normal (ZN)], which represents normal cultureconcentrations (Clonetics); 16 µmol/l of zinc [zinc adequate (ZA)],which represents normal human plasma zinc levels; or 32 µmol/l ofzinc [zinc supplemented (ZS)], which represents the high end ofplasma zinc levels attainable by oral supplementation in humans.Compared with ZN cells, cellular zinc levels were 76% lower in ZDcells but 3.5-fold and 6-fold higher in ZA and ZS cells, respectively.Abundances of p53 mRNA and nuclear p53 protein were elevatedin treatment groups compared with controls (ZN). For p53mRNA abundance, the highest increase (3-fold) was observed in ZD cells.In contrast, the highest increase (17-fold) in p53 nuclearprotein levels was detected in ZS cells. Moreover, gadd45mRNA abundance was moderately elevated in ZD and ZA cells and was notaltered in ZS cells compared with ZN cells. Furthermore, the onlyalteration in c-fos mRNA and caspase-3 activity was thetwofold increase and the 25% reduction, respectively, detected in ZScompared with ZN cells. Thus p53, gadd45, andc-fos and caspase-3 activity appeared to be modulated bycellular zinc status in NHBE cells.

     

Physiological studies of a hybrid between populations of Dactylis glomerata from contrasting climatic regions. II. Intra population variation

Mushroom compost was treated with nematicides and infested with Aphelenchoides composticola at the time of filling into growing containers. Yields of mushrooms from infested untreated control composts were reduced to 40–60% of yields from uninfested control compost. Yields from infested compost treated with fenamiphos emulsifiable concentrate (e.c.) at 10 or 20 mg a.i./kg, thiabendazole wettable powder at 40 or 60 mg a.i./kg or oxamyl granules at 20 mg a.i./kg were as high as from uninfested controls. Compost treated with granules of AC 64,475 up to 20 mg a.i./kg or ethoprophos or thionazin up to 80 mg a.i./kg gave yields significantly lower than uninfested controls. Numbers of nematodes rose to about 10⁶/20 g of compost in untreated compost and then fell, and a similar peak occurred in treatments in which yields were substantially reduced by nematode damage. Treatments which yielded as well as the uninfested controls held maximum nematode numbers down to about 10V20 g of compost but populations stayed at this level or tended to rise while numbers in untreated compost fell. Incorporation of fenamiphos in casing or its application to the surface of beds 3 wk after cropping began gave lower yields than the uninfested control but mushrooms were being produced late in the cropping cycle. Fenamiphos e.c. at 20 mg ai./kg incorporated in compost is considered a practical preventive measure for control of A. composticola.     

Shikimic Acid in the Leaves of Eucalyptus sieberiana F. Muell.

Shikimic acid was determined in leaves, at different stagesof growth, from 1- and 4-year-old specimens of Eucalyptus sieberianaF. Muell. A linear relationship was found between the shikimicacid concentration (mg./g.) and the weight of the leaf up tothe point where the leaf had reached full size. As the leavesbecame older the shikimic acid content decreased.     

Effect of sub-lethal concentrations of permethrin on ovary activation in the predator Supputius cincticeps (Heteroptera: Pentatomidae).

Insecticides may cause mortality and deleterious effects on predatory stinkbugs. For this reason, the effect of five concentrations of permethrin applied on third instar nymphs of Supputius cincticeps (St?l) (Heteroptera: Pentatomidae) was investigated on ovary activation in this predator. The nymphs received topical application of permethrin in the following concentrations (mg a.i./ml): 10(-7), 10(-6), 10(-5), 10(-4), and 10(-3). Ovary lengths and oocyte numbers were quantified following first egg mass. Ovary length of S. cincticeps varied from 5.7 mm with 10(-4) mg a.i./ml, to 6.4 mm with 10(-7) mg a.i./ml, with similar values for the other permethrin concentrations and for the control. The number of oocytes per female varied from 13.5 with 10(-3) mg a.i./ml, to 29.2 for the control, with significant differences. The number of oocytes per female of nymphs exposed to a permethrin concentration of 10(-5) mg a.i./ml was similar to that of the control. However, the lower number of oocytes per female from nymphs exposed to other concentrations of permethrin suggests that this insecticide may affect the reproductive capacity of this predator. The results obtained are discussed in relation to tolerance of Heteroptera predators to insecticides and possible hormesis occurrence.     

A sodium ion concentration gradient formed during the absorption of glycine by mouse ascites-tumour cells

1. To deplete them of ATP the tumour cells were starved at 37 degrees in a Ringer solution containing 33m-equiv. of Na(+)/l., 131m-equiv. of Li(+)/l., 2mM-sodium cyanide and 0.1mm-ouabain. The cellular content of K(+) was largely replaced by Li(+), but cellular [Na(+)] remained near 33m-equiv./l. 2. The addition of 12mm-glycine to the system caused cellular [Na(+)] to increase, during the next 4min., by about 4m-equiv./l., so that it slightly exceeded extracellular [Na(+)]. This occurred in parallel with the absorption of glycine. 3. The cellular K(+) content fell by an amount representing about 10% of the amount of Na(+) absorbed. 4. The results provide a clear demonstration that the flow of glycine into the cells is linked to a parallel movement of Na(+); K(+) appears to play a facultative role in the carrier system, whereas Li(+) is almost inert. 5. The effects produced by glycine were not reproduced by l-arabinose.     

Effects of Indol-3yl Acetic Acid on the Citrate-Condensing Reaction by Preparations of Root and Shoot Tissue

Preparations of citrate condensing enzyme (citrate oxaloacetate-lyase(CoA-acetylating) E. C. 4. 1. 3. 7) from root and shoot tissueof 5-day-old bean seedlings (Phaseolus vulgaris L., var. Burpee'sStringless Greenpod) had different activities, expressed asreaction rate per unit of fresh tissue. Activity per mg proteinwas increased when protein concentrations of the preparationswere reduced by dilution. Addition of indol-3yl acetic acid(IAA) enhanced activity of both root and shoot preparations.The effect was optimal at a concentration of 1.25x10^-4 M andthe enzyme was inhibited at 1.25x10^-3 M. Enhanement was greaterin root than in shoot preparations and in mixtures of equalamounts of each prepartion activity was intermediate betweenthose of the separte enzymes in absence of IAA but in its presenceapproached that of the shoot preparation. Apparent citrate synthesis in vivi was increased in shoots by application of IAA but therewas no such effect in roots.