Transformation of phenoxyacetic acid herbicides by Phaseolus vulgaris L. callus cells

The auxin herbicide (4-chloro-2-methylphenoxy)-acetic acid (MCPA) was absorbed by liquid cultured callus cells of Phaseolus vulgaris L. and subsequently became hydroxylated at the methyl group. The alcohol remained largely unconjugated and was partly released to the culture medium. Several glycosides and an ether-soluble conjugate of MCPA appeared as minor metabolites. Unsubstituted phenoxyacetic acid (POA) was metabolised primarily by 4-hydroxylation and subsequent phenolic glucoside formation. Metabolites of POA were retained by the cells. In the case of both substrates, metabolism in cells correlated well with that observed in apical buds excised from etiolated seedlings.Abbreviations MCPA (4-chloro-2-methylphenoxy)-acetic acid - OH-MCPA (4-chloro-2-hydroxymethylphenoxy)acetic acid - POA phenoxyacetic acid - 4-OH-POA 4-hydroxyphenoxyacetic acid     

Phytochrome Control of Its Own Synthesis in Pisum sativum

An analysis of phytochrome synthesis in Pisum seedlings by measuringthe activity of polysomal polyadenylated RNA (poly-A⁺-RNA) codingfor phytochrome apoprotein showed phytochrome control of itsown synthesis; brief red-light irradiation of pea seedlingsinhibited the activity of the RNA, and the red-light effectwas red/far-red reversible. ⁴ Permanent address: Biology Department, Faculty of Science,University of Tokyo, Hongo, Tokyo 113, Japan. (Received August 13, 1984; Accepted September 17, 1984)     

Salt Tolerance in Suaeda maritima (L.) Dum: THE EFFECT OF SODIUM CHLORIDE ON GROWTH, RESPIRATION, AND SOLUBLE ENZYMES IN A COMPARATIVE STUDY WITH PISUM SATIVUM L

The effect of sodium, chloride on the growth of a halophyte,Suaeda maritima (L.) Dum., was compared with its effect on Pisumsativum L. cv. Alaska under controlled environmental conditions.The salt stimulated the growth of Suaeda maximally at concentrationsof 170 to 340 mM while the growth of Pisum was inhibited evenby 100 mM. Both species accumulated ions in the tops and themaximum concentrations of Na⁺ and Cl^– rose in Suaeda to860 mM (based on the water content) and 730 mM and in Pisumto 170 mM and 300 mM respectively. Respiration in both specieswas inhibited as the NaCl level in the culture solution wasraised. Four supernatant enzymes (malic dehydrogenase, glucose-6-phosphatedehydrogenase, peroxidase, and acid phosphatase) prepared fromPisum and from Suaeda (grown either in the absence of addedNaCl or in the presence of 340 mM NaCl) were assayed in variouslevels of sodium chloride. The dehydrogenases were markedlyinhibited by increasing salt concentrations while there wasa smaller effect on the peroxidase and acid phosphatase. Therewas no difference in the effect of salt on the enzymes preparedfrom the two species although one is halophilic and the otherhalophobic.     

CO2-Fixation, Glycolate Formation, and Enzyme Activities of Photorespiration and Photosynthesis during Greening and Senescence of Sunflower Cotyledons

Time-courses of ¹⁴CO₂-fixation and of enzyme activities involvedin photorespiration and photosynthesis were determined duringthe life span of cotyledons from sunflower seedlings (Helianthusannuus L.). Glycolate formation in vivo was estimated from theresults of combined labelling and inhibitor experiments. NADPH-glyceraldehyde-3-phosphatedehydrogenase, NADPH-glyoxylate reductase and chlorophyll werewell correlated with the time-course of ¹⁴CO₂-fixation (photosynthesis).There was, however, a considerable discrepancy between the developmentalsequence of photosynthesis and that of both ribulose-l,5-bisphosphatecarboxylase and glycolate oxidase. Furthermore, time-coursesof glycolate oxidase activity in vitro and of glycolate formationin vivo differed significantly. Therefore, the use of glycolateoxidase as a marker for the activity of photorespiration ingreening sunflower cotyledons may be questionable. Results from¹⁴CO₂-labelling experiments with cotyledons treated with theglycolate oxidase inhibitor 2-hydroxy butynoic acid suggestthat glycolate formation relative to CO₂-fixation is reducedin senescent cotyledons. Key words: Development, glycolate oxidase, photorespiration, ribulose-l,5-bisphosphate carboxylase, oxygenase     

Effect of malformin on root growth

Malformin induces curvatures, stimulates root hair and lateralroot formation, promotes radial expansion, inhibits elongation,wet and dry weight, cell division and cell wall synthesis inroots of Zea mays, but has no effect on protein synthesis. Thegrowth curves (elongation, wet and dry weight) of Z. mays rootstreated with malformin are cubic. Processes which are involvedin inhibition of elongation are considered the primary causeof root curvatures by malformin. ¹This research was supported by grant GB-7158 from the NationalScience Foundation and grant E-146-F from the American CancerSociety. Journal Paper No. 3536 of the Purdue Agricultural ExperimentStation. ²Present address: Volcani Institute of Agricultural Research,P.O.B. 6, Bet-Dagan, Israel. (Received December 24, 1969; )     

The Uptake of Growth Substances: V. VARIATION IN THE UPTAKE OF A SERIES OF CHLORINATED PHENOXYACETIC ACIDS BY STEM TISSUES4GOSSYPIUM HIRSUTUM AND ITS RELATIONSHIP TO DIFFERENCES IN AUXIN ACTIVITY

When segments excised from the etiolated hypocotyls of Gossypiumhirsutum are pretreated in buffer, the subsequent uptake ofradioactive 2,4-dichlorophenoxyacetic acid (2,4-D-1-¹⁴C) isdepressed and the net loss of radioactivity which normally followsa phase of positive uptake by freshly excised segments doesnot take place. Uptake by fresh segments, in contrast with uptakeafter pretreatment, has a high Q₁₀ and is markedly depressedby both 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 3-indolylaceticacid. On these grounds it is proposed that net loss resultsfrom the release of material accumulated by a specific mechanismwhich, with time, becomes inoperative. Additional experimentssuggest that part of the 2,4-D taken up by stem segments ofTriticum vulgare and Avena sativa is accumulated by a similarmechanism. For 1-cm segments, entry is most rapid through the cut ends,and the effects of pretreatment exert their maximal effectsin the tissue near the ends. Therefore very short segments havebeen used to compare the courses of uptake of phenoxyaceticacid (POA) and its 2-, 4-, 2,6-, 2,4- and 2,4,5- chloro- derivatives.The patterns observed are similar to those previously reportedfor 1 -cm segments, although the differences between compoundsare greater. The courses of uptake of 2,4-D and 2,4,5-T, bothterminate in a phase when there is a net loss. POA and the 2-chloro-substitutedacid (2-CPA) are both continuously accumulated. No net lossis found with either the 2,6- (2,6-D) or the 4- chloro (4-CPA)compounds but the rates of uptake progressively decrease toa low level. It is proposed that the processes which determine the patternof uptake of chlorinated phenoxyacetic acids include two typesof accumulation. With Type I accumulation the mechanisms involvedrapidly become disorganized after tissues are excised from theplant. Type 2 accumulation, on the other hand, is stable. Theavailable data indicate that Type I accumulation is peculiarto compounds with marked auxin-like properties.     

The Uptake of Growth Substances: XV. THE DIFFERENTIAL EFFECTS OF PROGRESSIVE CHLORINATION OF PHENOXYACETIC ACID ON ENTRY INTO THE EPIDERMAL AND CUT SURFACES OF STEM SEGMENTS

The comparative patterns of entry into segments with sealedand open ends, excised from etiolated internodes of Pisum sativum,have been examined for phenoxyacetic acid (POA) and its 2-,4-, 2,4-, 2,6-, 3,5-, 2,4,5- and 2,4, 6-chloro derivatives,each containing ¹⁴C in the carboxyl group. Sealing the ends greatly depresses the level of entry, on averagean eight-fold reduction at 9 h. Likewise, the interrelationsbetween the degree of chlorination and uptake potential aredisparate. For segments with exposed cut surfaces the finalcontent is maximal for POA and the 2-chloro compound and minimalfor the 3,5-dichloro derivative (3,5-D) with an eight-fold difference.With sealed ends this difference is reduced to two-fold butwhile 3,5-D accumulates least uptake is now highest for POAand 2,4-D. There are also changes in the order with time. Initially,2,4,5-T penetrates fastest into sealed segments but for segmentswith open ends entry is most rapid for the 4- and 2,4,6-chloroderivatives. Additions of streptomycin and cetyltrimethylammoniumbromide(CTAB) induce differential changes in the patterns of uptake.Where uptake is promoted the enhancement is not restricted toactive auxins. Sealing the ends may alter the nature of theresponse. The likely physico-chemical and metabolic processes concernedin the two routes of entry are discussed and the results comparedwith previous divergent findings on the relationship betweenchemical structure and uptake by Lemna minor and penetrationinto leaves of Phaseolus vulgaris.     

Chemical Composition of Bleeding Xylem Sap from Kiwifruit Vines

A study of the chemical composition and charge balance was madeof bleeding xylem sap collected from excised one-year-old extensionshoots of healthy, Mn-deficient, Mn-toxic and Zn-deficient kiwifruitvines (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson)immediately prior to leafburst. The exudates were analysed formacronutrient cations and anions, trace elements, amino acids,organic acids and sugars. Major charged species measured wereCa (13.3 mM), K (8.9 mM), Mg (5.6 mM), malate (12.5 mM) andphosphate (5.8 mM). Glutamine (12 mM) was the predominant Ncarrier identified, accounting for 58 per cent of the totalN followed by NO₂^–-N (4.5 per cent), NH₄⁺-N (3.5 per cent)and arginine-N (2.9 per cent). Approximately 22 per cent ofthe N was in a hydrolysable proteinaceous fraction comprisingmainly glutamine and glutamate. Eighteen free proteinaceousamino acids were idetified in sap, the most abundant being glutamine,glutamic acid, valine, isoleucine and phenylalanine. Computersimulation of the chemical composition predicted that in additionto hydrated cations, ion pairs formed between inorganic components(SO₄^2–, HPO₄^2–, H₂PO₄^–) and cations (Ca²⁺,Mg²⁺, Mn²⁺), plus metal-organic ligand complexes (Ca Malate,Zn Malate, FeCit, CuHis, CuGln) are important species involvedin translocation. The solubility product of hydroxyapatite wasexceeded in all exudates although in vitro precipitation wasnot observed. To achieve electroneutrality with the componentsmeasured, however, formation of precipitate precursors (hydroxyapatitenuclei) had to be assumed. Irregularities in Mn nutrition (butnot Zn) were clearly indicated by the elemental compositionof exudate suggesting the use of sap analysis as a possiblepre-season indicator of nutritional status for this species. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson, kiwifruit, xylem sap composition, trace metals, amino acids, organic acids     

Short-term Effects of Heat-girdles on Source Leaves of Vicia faba: Analysis of Phloem Loading and Carbon Partitioning Parameters

Petiole heat-girdle treatments (followed by a 5 min ¹⁴CO₂ assimilation)were performed on mature leaves of Vicia faba, in order to assesstheir effect on the partitioning of photo-assimilates to theminor vein phloem. Whole leaf autoradiographic evidence indicateda high leaf-to-leaf variation in the image intensity over theminor veins (relative to the mesophyll/epidermal background)in both control and heat-girdled groups of leaves. The averagedegree of minor vein labelling in heat-girdled leaves, however,was found to be significantly lower than that in controls. Comparativeassessment of vein labelling was based on microscopic densityreadings of silver grains over veinal and interveinal regionsin autoradiographic images. Investigations into the cause ofthis alteration in vein labelling indicated no involvement ofan inhibition of apoplasmic phloem loading, as both heat-girdledand control leaves of Vicia were shown to have comparable minorvein uptake of exogenously supplied ¹⁴C-sucrose. Heat-girdlingwas shown, however, to increase significantly the partitioningof recently fixed carbon into the insoluble (mainly starch)fraction relative to the ethanol-soluble fraction, within 12min of the treatment. We suggest that this carbon partitioningchange can primarily account for the change in vein labelling,since an increase in the insoluble fraction would result in(1) more ¹⁴C-activity remaining in the leaf mesophyll and (2)less ¹⁴C-activity going into the mesophyll export pool, andthus, less ¹⁴C-sucrose being transferred to the minor vein region.Additionally, although leaf export was completely halted inheat-girdled leaves, ¹⁴C-activity was found within the majorveins as far as the point of petiole heat-girdling (followinga 5 min assimilation and 4 h chase). Apparently, continued (butlimited) solution flow within the sieve elements is maintainedby transport pathway unloading within the treated leaves. Key words: Phloem loading, carbon partitioning, heat-girdle, Vicia faba     

UDP-Glucose: Sterol Glucosyltransferase and a Steryl Glucoside Acyltransferase Activity in Amyloplast Membranes from Potato Tubers

Envelope membranes were isolated from potato tuber amyloplastby a discontinuous sucrose density gradient and high speed centrifugation.These membranes catalyzed the transfer of [¹⁴C]glucose fromUDP-[¹⁴C]glucose to endogenous sterol acceptors and, in turn,catalyzed the esterification of steryl glucosides with fattyacids from an endogenous acyl donor. The synthesis of sterylglucosides was stimulated in the presence of Triton. X-100,while formation of acyl steryl glucosides was inhibited by thedetergent. However, in the presence of an added sterol acceptorand Triton X-100, the inhibition of acyl steryl glucoside synthesiswas overcome by the addition of phosphatidylethanolamine. Theenzyme involved in steryl glucoside formation was solubilizedby treatment of the envelope membranes with 0.3% Triton X-100.The solubilized enzyme had an almost absolute requirement forsterol acceptors. Key words: Solanum tuberosum, Sterol glucosylation, Steryl glucoside acylation, Amyloplast membrane     

Effect of Phytochrome on the Uptake of Gibberellin by Protoplasts of Nicotiana glutinosa L.

The effect of red light on gibberellin uptake by Nicotiana glutinosaL. protoplasts was determined. Five minutes of red light causedover a 50% inhibition of GA₃ uptake within 2 minutes. Five minutesof far red light completely reversed the red light effect. Theantagonistic effect of far red light indicates that gibberellinuptake is under phytochrome control. The rapid inhibition of gibberellin uptake indicates that phytochromeregulates the permeability properties of the plasma membraneas an initial response and not the intracellular binding ofgibberellin. ¹Department of Plant Pathology, University of Missouri. (Received October 28, 1985; Accepted April 23, 1986)     

Metabolic Alterations Associated With Abscisic Acid-Induced Frost Hardiness in Bromegrass Suspension Culture Cells

Metabolic alterations associated with the induction of freezingtolerance by abscisic acid (ABA) were characterized by chemicalanalysis and by [U-^l4C]sucrose partitioning into cellular constituentsin bromegrass (Bromus inermis Leyss cv. Manchar) cell suspensioncultures. ABA caused a significant elevation in dry matter,particularly in the fraction insoluble in 85% ethanol, thatwas highly correlated with enhanced frost tolerance. Cell walls,the largest component of the insoluble fraction, increased significantlyas frost tolerance increased throughout the ABA treatment period.ABA stimulated total [¹⁴C]sucrose uptake by cells from 7% onday 1 to 97% on day 7 compared to control cells. Partitioningstudies detected a significant increase in ¹⁴CO₂ evolution at3, 5 and 7 days after ABA treatment and a significantly higherincorporation of [¹⁴C]sucrose into the ethanol insoluble fractionafter 5 and 7 days of treatment. Organic acid depletion in ABA-treatedcells was also highly correlated with the increase in hardiness.The concentration of total sugars was higher in ABA-treatedcells. The results indicate that most of the metabolic changesduring ABA-induced acclimation were similar to changes reportedfor cells acclimated in response to low temperature. ¹Oregon Agricultural Experiment Station Technical Paper No.9052 ²Present address: Department of Horticulture, University ofSaskatchewan, Saskatoon, Sask. Canada S7N 0W0 (Received November 1, 1989; Accepted March 13, 1990)     

Photosystem I and photophosphorylation-dependent leucine incorporation in the blue-green alga Anacystis nidulans

L-Leucine uptake and incorporation in the blue-green alga Anacystisnidulans were measured during illumination with monochromaticlight of 630 and 717 nm. With near as well as far red light,an enhanced uptake of ¹⁴C-L-leucine was observed. In far redlight, the leucine uptake depended on light intensity and pHvalue. After the first few minutes, the uptake remained constantfor more than one hour. The rate of uptake in light was thesame in air as in nitrogen. The incorporation of ¹⁴C-leucinein the soluble fraction decreased in the presence of chloramphenicolwhich prevents protein synthesis. In far red light, its incorporationwas insensitive to DCMU (5 ? 10^–6 M) but was depressedby uncouplers like CCCP or desaspidin. These effects are takenas evidence that leucine incorporation under the conditionsused is dependent on photosystem I reactions and cyclic photophosphorylation.DBMIB and KCN in high concentrations decrease the leucine incorporationin far red light and indicate that plastoquinone and plastocyaninare members of the cyclic electron flow also in intact cellsof Anacystis. Antimycin A has no inhibitory effect. The inhibitionby other less specific inhibitors like salicylaldoxime, desaspidinand DSPD is discussed. (Received August 19, 1978; )     

Some Properties of an Acid Phosphatase Isolated from the Seed Coats of Developing Pea Seeds

An acid phosphatase (EC 3 1 3 2)isolated from the seed-coatsof developing pea seeds was estimated to have MW 30000 by gelfiltration on Sephadex G-75 It was shown to act on a broad spectrumof physiological substrates, the most preferred being ß-glycerophosphate,3-phosphoglycerate and ADP, wich all showed rates of about halfthe maximum rate shown with p-nitrophenyl phosphate (p-NPP)Another model substrate frequently used in enzyme localizationstudies, -naphthyl acid phosphate, was hydrolysed at about 30% of the rate shown with p-NPP This acid phosphatase was enhancedor stabilized by the chelators EDTA and 1, 10-phenanthrolme,unaffected by Mg²⁺ and N-ethyl maleimide, but strongly inhibitedby Zn²⁺ and F^– Both oxidized and reduced glutathione werewithout effect at low concentration and slightly inhibitoryat high concentration (15 mm) Thiol groups are clearly not involvedin regulating the activity of this acid phosphatase, a featurewhich distinguishes it from acid phosphatases from several otherplant species. Pisum sativum L, pea, acid phosphatase, seed-coats, seed development     

Increased vacuolar and plasma membrane H+-ATPase activities in Salicornia bigelovii Torr. in response to NaCl

The halophyte Salicornia bigelovii Torr. shows optimal growthand Na⁺ accumulation in 200 mM NaCl and reduced growth underlower salinity conditions. The ability to accumulate and compartmentalizeNa⁺ may result, in part, from stimulation of the H⁺ -ATPaseson the plasma membrane (PM-ATPase) and vacuolar membranes (V-ATPase).To determine if these two primary transport systems are involvedin salt tolerance, shoot fresh weight (FW) and activity of thePM- and V-ATPases from shoots in Salicornia grown in 5 and 200mM NaCI were compared. Higher PM-ATPase activity (60%) and FW(60%) were observed in plants grown in 200 mM NaCI and thesestimulations in growth and enzyme activity were specific forNa⁺ and not observed with Na⁺ added in vitro. V-ATPase activitywas significantly stimulated in vivo and in vitro (26% and 46%,respectively) after exposure to 200 mM NaCl, and stimulationwas Na⁺ -specific. Immunoblots indicated that the increasesin activity of the H⁺ -ATPases from plants grown in 200 mM NaCIwas not due to increases in protein expression. These studiessuggest that the H⁺-ATPases in Salicornia are important in salttolerance and provide a biochemical framework for understandingmechanisms of salt tolerance in plants. Key words: Salicornia, H⁺-ATPases, salt tolerance     

Pigment Bodies in Fruits of Crimson and High Pigment Lines of Tomatoes

Pigment bodies in fruits of crimson (og^c), high pigment (hp),and crimson-high pigment (og^c hp) lines of tomatoes were observedby electron and light microscopy and compared with those ofnormal red lines and a yellow cultivar. During chloroplast-chromoplasttransformation, two main structurally distinct bodies are produced,their total and relative amounts apparently accounting for theentire range of colours (from very deep red to yellow) characterizingthe mature fruits of these different colour lines. The longnarrow crystalloids, believed to be lycopene, form in associationwith an extended thylakoid system; in senescing (over-ripe)fruit many of these are reduced to shorter irregular forms.The rounded globules are believed to be beta-carotene dissolvedin lipid material derived from membrane lysis. Analytical resultscorroborate microscopic observations that the effect of theog^c gene, as compared with the r⁺ gene for normal red colour,is to increase the lycopene content and lower the beta-carotenecontent. The effect of the hp gene is to increase the levelsof both pigments. The results support the view that the genescontrol the development of fruit pigments which affect chromoplastultrastructure. Lycopersicon esculentum Mill, tomato, fruit, pigment bodies, beta-carotene, lycopene     

The Uptake of Growth Substances: VII. THE ACCUMULATION OF CHLORINATED BENZOIC ACIDS BY STEM TISSUES2

The courses of uptake of benzoic acid (BA) and its 2-chloro-(2-CBA), 2,4-dichloro- (2,4-DCBA), 2,5-dichloro- (2,5-DCBA),and 2,3,6-trichloro- (2,3,6-TCBA) derivatives, all containing¹⁴C in the carboxyl group, have been investigated, employingstem segments of Pisum sativum, Gossypium hirsutum, and Avenasativa. From comparisons of the rates of accumulation by segmetns ofdifferent length it is conclueded that for each compound uptakeproceeds largely or wholly via the cut surfaces. The initial uptake of BA and 2-CBA by segments of Pisum is depressedas the pH of the solution is raised from 4 to 6.5, but the fallis less rapid than the decrease in the proportion of undissociatedmolecules. For all three species, BA and 2-CBA, which induced no extensiongrowth, were accumulated at a more or less constant rate. Bycontrast, the course of uptake of 2,3,6-TCBA, a powerful auxin,exhibited marked deviations from a linear pattern, especiallyin Avena where uptake became negative between four and six hours.This loss of radioactivity from the tissues was due to the netegress of 2,3,6-TCBA itself into the external solution. In Avenathe two dichloro-benzoic acids (2,4-DCBA and 2,5-DCBA) haveintermediate trens: net accumulation declined almost to zerobut subsequently recovered and proceeded at a rapid rate. These findings are discussed in relation to prior studies ofthe uptake of substituted phenoxyacetic acids and the conceptsof Type 1 and Type 2 accumulation. It is proposed that accumulationof BA and 2-CBA is largely governed by a stable Type 2 processwhile the initial uptake of the powerful auxins, 2,3,6-TCBAand 2,5-DCBA proceeds via an unstable system, similar or identicalto Type 1 accumulation.     

Inorganic Carbon Transport and Fixation in Cells of Anabaena variabilis Adapted to Mixotrophic Conditions

The Cyanobacterium Anabaena variabilis ATCC 29413 grown at lowCO₂ concentration under mixotrophic conditions with fructoseshowed a repression in the ability to fix inoganic carbon. Thisrepression was not due to a diminution in the ability to transportexternal inorganic carbon but could be explained by a decreaseof two enzymatic activities involved in the assimilation ofinorganic carbon: carbonic anhydrase and Rubisco. Carbonic anhydraseactivity was close to 50% lower in mixotrophic than in autotrophiccells. Moreover growth under mixotrophic conditions reducedRubisco activity at all dissolved inorganic carbon concentrationsassayed (5–60 mM). Maximum Rubisco activity (V_max decreasedfrom µmol CO₂ mg protein^-1h^-1 in autotrophic cells to2.3 µmol CO₂ mg protein^-1h^-1 in mixotrophic cells. Nosignificant differences in K_m(C₁) between autotrophic and mixotrophiccells were however observed. The possible mechanisms involvedin the inhibition of Rubisco are discussed. (Received November 8, 1994; Accepted October 12, 1995)     

Relation between Sex Expression Types and Cotyledon Etiolation of Cucumber in vitro I. On the Role of Ethylene Evolved from Seedlings

Cucumber seedlings, when cultured in vitro, showed differencesin cotyledon etiolation rates among cultivars with differentgenetic backgrounds for sex expression. The chlorophyll contentin gynoecious cultivars (acr^F/acr^F) decreased rapidly whilethat in monoecious ones (acr⁺/acr⁺) decreased more slowly, andthat in mono-gynoecious ones (acr¹/acr¹) decreased at an intermediaterate. Etiolation was suppressed even in early-etiolating cultivarswhen the flask remained unsealed or endogenously evolved ethylenewas removed. Cotyledon etiolation was enhanced even in late-etiolatingcultivars when ethephon was added to the flask. The rate ofetiolation corresponded to the ethylene concentration in theflask; much more ethylene was detected in early-etiolating cultivarsthan in late-etiolating ones. Ethylene accumulation is one of the important factors involvedin the cotyledon etiolation observed in in vitro cultures. Thedifference in etiolation rates among seedlings with differentgenetic backgrounds for sex expression corresponds to theirability for ethylene evolution, in the order of acr^F>acr¹>acr⁺. (Received January 6, 1981; Accepted March 23, 1981)     

The Inducible Formation and Stability of Nitrate Reductase in Higher Plants: II. EFFECTS OF ENVIRONMENTAL FACTORS, ANTIMETABOLITES, AND AMINO-ACIDS ON INDUCTION

The induction of nitrate reductase by molybdenum or nitratein excised tissues of cauliflower leaf was dependent on temperature;for the range 2^? to 12^? C, Q₁₀ was about 2; for the range 12^?to 22^? C, Q₁₀ was greater than 3. Enzyme formation was initiallymost rapid at 32^? C but did not continue for as long as it didat 22^? or 24^? C. Decreased oxygen supply lessened the rate ofenzyme formation. The effects on enzyme formation of a widerange of natural and synthetic antimetabolites were tested withrespect to induction by either nitrate or molybdenum, when introducedat the same time by infiltration. Actidione (cycloheximide),patulin, cycloserine, polymyxin B, L-2-thiolhistidine D-methionine,L-dihydroxyphenylalanine, D,L--methylglutamic acid, sarcosineand 1 ,2-dichloro-4-(p-nitrobenzenesulphonylamido)-5-nitrobenzene(DCDNS) were the most inhibitory compounds tested. Serine stimulatedproduction of enzyme activity; kinetin, benzimidazole, and p-fluorophenylalanine,3--methyltryptophane and the 4- isomer, chloramphenicol, gramicidin,and several thio- and^aza- derivatives of purines or pyrimidineswere practically without effect. Differential effects of inhibitorson enzyme formation in response to nitrate or molybdenum wererarely observed, and no deductions regarding the possible sequencein which the substrate and prosthetic metal induce activitycould be inferred from the results.