Bl?tenbildung bei Lemna paucicostata 6746 durch kombinierte Anwendung von Abscisins?ure und GCG

To a certain extent the flowering of Lemna paucicostata 6746is evoked in continuous light by application of abscisic acid(ABA) and CCC. Moreover, the action of the combined substancesappears in two separate concentration ranges. In the range ofABA 2?10^–9 M/CCC 10^–7–10^–6 M floweringis initiated without inhibition of vegetative growth and proceedsonly in the presence of high intensity light and sucrose. Acombination of ABA 2?10^–5 M/CCC 10^–3M simultaneouslycauses a strong inhibition of frond multiplication. Here theeffect can be observed also under low intensity light conditionsand without sucrose in the medium. A range with flower inhibitingactivity lies between the two flower promoting concentrationranges. (Received November 16, 1972; )     

MORPHOGENESIS IN SPIEODELA OLIGORRHIZA: EFFECTS OF PYRIMIDINE BASE ANALOGUES ON INITIATION, ELONGATION AND DIFFERENTIATION OF FRONDS

The effect of four pyrimidine base analogues and their antidoteson S. oligorrhiza was studied. FUdR stopped cell division at concentrations of 4 10^–7M and higher. This effect could be nullified by the additionof 4 10^–6 M thymidine. Neither uridine nor uracil hadan antidotal effect on FUdR. FU (8 10^–6 M or higher concentration) affected celldivision, frond elongation and differentiation, and could notbe counteracted by either thymidine or uracil. TU (8 10^–4 M) rather specifically inhibited differentiationof frond tissues, while not preventing cell division or theinitiation of new generations. Uracil and uridine at about equimolarconcentrations completely counteracted the TU effect. AzU (10^–3 M) suppressed cell division, frond elongationand frond differentiation. When thymidine (10^–3 M) wasadded simultaneously with AzU only cell elongation and differentiationof fronds were inhibited, but cell division proceeded. 10^–3M uracil (but not uridine) counteracted all effects of AzU. ¹ Based on a portion of the senior author's Ph.D. Thesis.     

Release of Guttation Fluid from Passive Hydathodes of Intact Barley Plants. II. The Effects of Abscisic Acid and Cytokinins

Guttation was used as a non-destructive way to study the flowof water and mineral ions from the roots and compared with parallelmeasurements of root exudation. Guttation of the leaves of barley seedlings depends on age andon the culture solution. Best rates of guttation were obtainedwith the primary leaves of 6- to 7-day-old seedlings grown onfull mineral nutrient solution. The growing leaf tissue becomessaturated with K⁺ below 1.5 mM K⁺ in the medium, whereas K⁺concentration in the guttated fluid still increases furtheras K⁺ concentration in the medium is raised. At 3 mM K⁺ averagevalues of guttation were 1.4–2.4 mm³ h^–1 per plantwith a K⁺ concentration of 10–20 mM; for exuding plantsthe flow was 4.2–7.6 mm³ h^–1 per plant and K⁺ concentration35–55 mM. Abscisic acid (ABA) at 10^–6 to 10^–4 M 0–2h after addition to the root medium increased volume flow ofguttation and exudation and the amount of K⁺ exported. Threeh after addition of ABA both volume and amount of K⁺ were reduced.There was an ABA-dependent increase in water permeability (Lp)of exuding roots shortly after ABA addition. Later Lp was decreasedby 35 per cent and salt export by 60 per cent suggesting aneffect of ABA on salt transport to the xylem apart from itseffect on Lp. Benzyladenine (5 x 10^–8 to 10^–5 M)and kinetin (5 x 10^–6 M) progressively reduced volumeflow and K⁺ export in guttation and exudation and reduced Lp. Guttation showed a qualitatively similar response to phytohormonesas found here and elsewhere using exuding roots. Hordeum vulgare L., barley, guttation, abscisic acid, cytokinins, benzyl adenine, kinetin     

Removal of the sugar inhibition of flowering in Lemna gibba G3 by catecholamines

DL-Epinephrine (10^–8–10^–7 M), DL-norepinephrine(10⁶ M) and DL-isoproterenol (10^–8–10^–6 M)alleviated floral inhibition due to 1% of sucrose, in Lemnagibba G3. The induction period extended by sucrose was curtailedby epinephrine, frond multiplication enhanced by the sugar beingleft unaltered. The pattern of action of catecholamines appearedto be very similar to that of cAMP. DL-Epinephrine, however,was ineffective in the presence of 10^–7 M DL-propranololwhich affected neither flower nor frond production by itself.Quabain and nicotinic acid also nullified the epinephrine actionon duckweed flowering. These and other relevant findings supportthe hypothesis that the cAMP-adenyl cyclase system participatesin the processes of flower induction in this long-day plant. (Received August 21, 1973; )     

Effect of abscisic acid on differentiation and ribulose diphosphate carboxylase of chloroplasts

Daucus carota tissues were grown on Murashige-Skoog medium (MS)at different concentrations with abscisic acid (ABA). Sevenbands of chloroplast fractions were obtained on a sucrose gradient.At 10^–5M, ABA highly increased chlorophyll and proteinnitrogen content of medium density chloroplasts. With increasingage of the tissues, the most active chloroplasts according totheir ¹⁴CO₂ fixation were found in smaller numbers. When treatedwith 10^–5 M ABA, 34 day-old tissues cultivated in vitroshowed the chloroplast pattern of 110 day-old tissues. The effectof ABA—given to the tissues during a short pretreatmentor continuously present in the culture medium—on the ribulosediphosphate carboxylase activity was analysed. It was foundthat ABA at 10^–5 M strongly inhibited ¹⁴CO₂ fixation. (Received December 20, 1977; )     

Frond and flower production in Lemna gibba G 3 in presence of respiratory inhibitors

Effects of respiratory inhibitors on frond and flower productionin light culture of a long-day duckweed, Lemna gibba G 3, wereinvestigated. The inhibitors examined could be divided into3 groups based on their specific actions: (A) 2,4-Dinitrophenol(10^–6M), arsenate (10^–4M), malonate (10^–2M),o-phenanthroline (10^–6M), ,'-dipyridyl (10^–5M) andazide (10^–6M) inhibited flower production by suppressingthe rate of flower production without affecting the inductionperiod. Frond production, however, was promoted by these reagents.Effective time of application came one day after the end ofthe induction period. (B) Iodoacetate (10^–6M) and fluoride(10^–4M) inhibited both flower production and, less significantly,frond production. Reduced rate of flower production was responsiblefor the inhibition of flowering. Effective time of applicationpreceded by one day that of A group inhibitors. (C) Salicylaldoxime(10^–6M), diethyldithiocarbamate (10^–6M) and 8-hydroxyquinoline(10^–7M) enhanced flower production by reducing the lengthof the induction period, and simultaneously slightly inhibitedfrond production. Effective time of application was the latterhalf of the induction period. The implications of these findingsare discussed with special reference to the component processesinvolved in photoperiodic induction of flowering in duckweed. (Received March 27, 1969; )     

Interaction of Abscisic Acid and Light on Leaf Senescence in Rice

The senescence of excised leaves of Oryza saliva L. cv. BAM11 was studied by monitoring the breakdown of chlorophyll andprotein. ABA at 10^–6 M retarded senescence until the 3rdday and accelerated it in a normal way until the 9th day inlight. The effect of ABA was light-dependent, which is beingreported for the first time in rice. ABA in the presence oflight (26.3 Klux) delayed protein breakdown but could not preventthe yellowing effect. (Received June 18, 1982; Accepted January 28, 1983)     

Abscisic Acid and Apical Dominance in Phaseolus coccineus L. The Role of Tissue Age

Abscisic acid (ABA) applied to the decapitated second internodeof runner bean plants enhanced outgrowth of lateral buds onlywhen internode stumps were no longer elongating. Applied toelongating internodes of slightly younger plants, ABA causesinhibition of bud outgrowth. Together with 10^–4 M indol-3-ylacetic acid (IAA), ABA stimulated internode elongation and interactedadditively in the inhibition of bud outgrowth. A mixture of10^–5 M ABA and 10^–6 M gibberellic acid (GA₃ ) causedsimilar effects on internode growth as IAA + ABA, but was mutuallyantagonistic in effect on growth of the lateral buds. Abscisic acid, apical dominance, gibberellic acid, indol-3yl acetic acid, Phaseolus coccineus, bean     

In vitro Regeneration from Excised Leaf Discs of Three Brassica Species

Excised leaf discs of three Brassica species, B. oleracea, B.napus, and B. campestris were induced to produce adventitiousbuds and subsequently entire plants by culture on media withspecific combinations of 6-benzylaminopurine (BAP) and -naphthylaceticacid (NAA). Each species required a particular hormone concentrationfor optimum growth and differentiation: B. oleracea, BAP 10mg^–1 and NAA 1 mg 1^–1; B. napus, BAP 10 mg 1^–1and NAA 10 mg 1^–1; B. campestris, BAP 1 mg 1^–1 andNAA 10 mg 1^–1. In a more detailed study on one of these species, namely B.oleracea, the relative influence of other media components suchas amino acids and other organic additives was examined. Itwas also found that the source and size of the explant greatlyaffected the growth response, as did the size of the culturevessel. The regenerated plants dislayed a range of ploidy as well asphenotypic abnormalities. Findings are discussed in relation to results from other tissueculture systems.     

Resemblance of growth substances to metal chelators with respect to their actions on duckweed growth

Action patterns of IAA, KIN and GA on the growth of Lemna gibbaG3 are similar to those reported for agents chelating both cupricand ferric ions. Relatively high doses of growth substances,e.g.10^–6 M IAA or KIN and ^–4 M GA, inhibit developmentof photoperiodically induced flower buds and antagonisticallypromote frond multiplication; whereas, at relatively low doses,e.g. 10^–9 M IAA or KIN and ^–5 M GA, they acceleratethe process occurring in the latter half of the induction periodto enhance flower induction. Complex forming abilities of IAA,KIN and GA with cupric and ferric ions are demonstrated spectrophotometrically.Moreover, the ferrous ion-dependent oscillatory change in reproductiveand vegetative photophilies of duckweed is eliminated by KINbut not by IAA and GA. Of the three growth substances tried,KIN alone shows an affinity for ferrous ions. (Received April 5, 1971; )     

Organogenesis in the Cultured Female Gametophyte of Ephedra foliata

The female gametophyte of Ephedra foliata was used as an explantfor the production of haploids as it is composed of haploidcells, all of the same genotype. The regeneration of roots wasdependent upon the presence of NAA, while BAP had a modifyingeffect. At lower concentrations (0.05 parts 10^–6 and 3.5parts 10^–6) BAP enhanced the root promotion of NAA (0.05–4.0parts 10^–6). At higher concentrations of BAP (1–6parts 10^–6), roots and shoot buds were formed. Kinetinat 4.0 parts 10–6 with 0.5 parts 10–6 2, 4-D wasoptimal for shoot bud production in explants at the archegonialstage and 2, 4-D at 2.0 parts 10–6 with 0.5 parts 10–6kinetin was optimal for root formation. Cells of the callusand root tip had the haploid number of chromosomes, n = 7. Meristemoidswere located on the surface or embedded in the callus tissue.The deep seated meristemoids organized only root primordia,but the peripheral ones gave rise to root as well as shoot budprimordia. Initially, there was no vascular connection betweenthe shoot-bud and the callus. This was established later. Key words: Ephedra, Female gametophyte, Haploid, Tissue culture     

Effect of abscisic acid on membrane-bound epidermal ATPase from tobacco leaves

Membrane-bound Mg⁺⁺-activated ATPase activity in epidermal stripsfrom tobacco leaves (Nicotiana tabacum L. Samsun NN) was stimulatedby abscisic acid (ABA) when the strips were floated on ABA solutionin light or in darkness. The optimum ABA concentrations in lightand in darkness were 10^–5 M and 10^–6 M, respectively.Carbonyl cyanide m-chlorophenylhydrazone (CCCP) and N, N'-dicyclohexylcarbodiimide(DCCD) completely blocked the basal level membrane-bound epidermalATPase activity. ABAinduced membrane-bound epidermal ATPaseactivity was completely inhibited by CCCP, but only partly byDCCD. H⁺-influx into epidermal strips on a solution in light was lowerthan that in darkness. ABA stimulated H⁺-influx into epidermalstrips in light and in darkness. CCCP suppressed basal levelH⁺-influx, whereas DCCD did not. CCCP also suppressed ABA-inducedH⁺-influx, whereas DCCD did not. Interaction between H⁺-influxand membranebound epidermal ATPase activity is discussed. (Received May 23, 1978; )     

Rates of Photosynthesis in Characean Cells: I. PHOTOSYNTHETIC 14CO2 FIXATION BY NITELLA TRANSLUCENS

A study has been made of photosynthetic ¹⁴CO₂ fixation by isolated‘mature’ internodes of Nitella translucens. Experimentalconditions were similar to those used in studies of the ionicrelations of these cells. Maximum rates of photosynthesis were33–40µµmoles CO₂, fixed per cm² of surfacearea per second (equivalent to 12–15 /xmoles fixed permg chlorophyll per hour). ^l4CO₂ fixation was inhibited to thedark level by 3(3,4,dichlorophenyl)-1, 1-dimethylurea (at 0-6µM or 10µM) and by the uncoupler carbonyl cyanide-m-chlorophenylhydrazone(SµM). The presence of imidazole or ammonium sulphate(both of which uncouple ATP production in vitro) did not resultin an inhibition of 14CO2 fixation. These results are discussedin relation to published work on solute uptake by Nitella translucens.During photosynthesis there was rapid movement of ¹⁴C-labelledorganic compounds out of the chloroplasts. ¹⁴C-labelled sucrose,ammo-acids, and sugar phosphates were found in samples of vacuolarsap.     

Stimulation of the Uptake of Sorbitol into Vacuoles from Apple Fruit Flesh by Abscisic Add and into Protoplasts by Indoleacetic Acid

The uptake of sorbitol into vacuoles from immature flesh ofapple fruit (Maluspumila Mill, var domestica Schneid.) was facilitatedby 10^–6 M ABA, while such uptake into protoplasts wasnot stimulated. By contrast, the application of 10^–5 MIAA facilitated uptake of sorbitol into protoplasts but didnot significantly into vacuoles. (Received July 17, 1990; Accepted December 25, 1990)     

Effect of Spermidine and Methylglyoxal-bis (Guanyl-hydrazone) (MGBG) on In Vitro Pollen Germination and Tube Growth in Catharanthus roseus

Incorporation of polyamine-spermidine into the nutrient mediumat 10^–6 and 10^–5 M concentrations stimulates pollen-tubegrowth in vitro in Catharanthus roseus L. G. Don. MGBG, an inhibitorof spermidine biosynthesis, at 0.5 x 10^–3 and 1 x 10^–3M concentrations reduced the percentage of germination as wellas tube growth and at a concentration of 1.5 x 10^–3 Mgermination was totally inhibited. Pollen grains incubated inthe medium containing 1.5 x 10^–3 M MGBG, when transferredto a fresh medium with 10^–5 M spermidine, resulted in80% germination recovery, along with considerable tube growth.Experiments with actinomycin-D indicate that stimulation ofpollen-tube growth by spermidine may involve de novo synthesisof protein. Catharanthus roseus, pollen germination, tube growth, spermidine, MGBG, inhibition, actinomycin-D     

Morphogenic Potential of Cultured Explants of Crocus chrysanthus Herbert. cv. E. P. Bowles

Explants of leaves, basal plates, petals, anthers and ovariesof young growing corms of Crocus chrysanthus var. E. P. Bowleswere cultured on MS basal media with 20 different combinationsof either kinetin and NAA or BAP and 2, 4-D in the dark. Nomajor change was observed except on ovary explants. The ovaryexplants produced callus at 5.0 mg 1^–1 and 10 mg^–1BAP and subsequently stigma-like structures formed on the surfaceof the callus. Transfer to light resulted in the stigma-likestructures developing a yellow pigmentation whereupon they cameto resemble the naturally-grown stigmas. Corm formation andshoot regeneration was obtained from the callus when the ovaryexplants were cultured on media containing 5.0 and 10 mg I^–1BAP with 0.5 mg 1^–1 2, 4-D. Increasing the level of 2,4-D markedly reduced the number of shoots produced per explant. Key words: Crocus chrysanthus, callus, ovary explants     

Microelectrophoretic and 9-Aminoacridine Fluorescence Study of the Surface Electrical Properties of Suspension Cultured Catharanthus roseus Cells and Isolated Protoplasts: Effects of Abscisic Acid Treatment

The effects of abscisic acid (ABA) treatments on the surfaceelectrical properties of cells and isolated protoplasts fromCatharanthus roseus cell suspension cultures were studied byelectrophoretic mobility and 9-aminoacridine (9AA) fluorescencemeasurements. The surface charge densities of the cells andprotoplasts estimated from electrokinetic data were –0.064Cm^–2and –0.048 C m^–2 respectively. These values wereclose to that estimated by 9AA fluorescence technique i.e.,–0.053 Cm^–2 for the cells and –0.041 Cm^–2for the isolated protoplasts accordingly. The net negative surfacecharge density decreased after application of 10 µM and50 µM ABA in both cells and protoplats, the more pronouncedeffect being observed at 10 µM ABA. When 100 µMABA was supplemented to the cell suspension culture the oppositeeffect was observed. The average charge density increased to–0.074 C m^–2 for the cells, and to –0.055C m^–2 for protoplasts, as revealed from the 9AA measurements.The results are discussed in terms of specific concentrationdependent ABA-induced alterations of the electrostatic propertiesof cell and protoplast membranes. (Received December 12, 1994; Accepted April 3, 1995)     

The Effects of Cytokinins and ABA on Stomatal Behaviour of Maize and Commelina

Epidermal strips and leaf fragments of Commelina and leaf fragmentsof maize were incubated on solutions containing naturally-occurringor synthetic cytokinins and/or ABA. The effects of these treatmentson stomatal behaviour were assessed. Cytokinins alone did notpromote stomatal opening in either species but concentrationsof both zeatin and kinetin from 10^–3 to 10^–1 molm^–3 caused some reversal of ABA-stimulated closure ofmaize stomata. The reversal of the ABA effect increased withincreasing cytokinin concentration. Cytokinins had no effecton ABA-stimulated closure of Commelina stomata. When appliedalone, at high concentration (10^–1 mol m^–3), toCommelina epidermis or leaf pieces both zeatin and kinetin restrictedstomatal opening. Key words: ABA, Cytokinins, Stomata, Maize, Commelina     

Effects of Abscisic Acid on Nucleic Acid Synthesis and the Induction of Nitrate Reductase in Lemna polyrhiza

Abscisic acid (ABA) at low concentrations brings about the formationof turions (dormant fronds) in Lemna polyrhiza within 3 to 5days after application. The incorporation of ³H-thymidine intoDNA, separated by polyacrylamide-gel electrophoresis, is inhibitedby 80 to 90 per cent within 1 to 3 h of ABA application. Theincorporation of ¹⁴C-orotate and ³²P into RNA is not inhibiteduntil 3 to 9 h after ABA application, but 70 per cent inhibitionis reached after 24 h on 10^–5 M ABA. There is little inhibitionof ¹⁴C-leucine incorporation into protein until 2 to 3 daysafter application of ABA. The capacity of nitrate to inducenitrate reductase in cultures previously grown on nitrate-freemedium is not affected by ABA even up to 3 days after application.The results are discussed in relation to the mode of actionof ABA.