Effects of a brassinosteroid on growth and electrogenic proton extrusion in maize root segments

In apical or subapical root segments of maize ( Zea mays L. cv. Dekalb XL640), 10⁻⁷–10⁻⁵ M 24-epibrassinolide (BR), a physiologically active synthetic epimer of the pollen hormone brassinolide, induces a significant stimulation of root growth, associated with an increase of acid secretion. The increase in acid secretion is enhanced by the presence of K⁺ in the medium and is accompanied by an early, significant hyperpolarization of the transmembrane electric potential (PD), which is completely suppressed by the addition of the protonophore uncoupler FCCP. Similar effects of BR have earlier been reported for shoots, and also for IAA in shoots. Contrariwise, 10⁻⁸–10⁻⁷ M IAA inhibits acid secretion and depolarizes the PD in the maize root segments. This suggests different pathways for the action of the two different hormones on the proton pump.     

Effect of 2-chloroethylphosphonic acid on capsule formation and alkaloid content in Papaver somniferum

Application of different concentrations of ethephon (2-chloroethylphosphonic acid) to Papaver somniferum L. at the times of stem elongation, bud, and capsule formation produced different effects. Ethephon (10^-2 M ) retarded growth of the plant and inhibited capsule formation during stem elongation, significantly reduced capsule size during the flowering period, but did not alter capsule development during capsule formation. When applied during the period of stem elongation, ethephon (10^-3 M and 10^-4 M ) reduced capsule size; alkaloid accumulation was reduced by ethephon at a concentration of 10^-3 M , but slightly increased by 10^-4 M . Ethephon (10^-3 M and 10^-4 M ) did not alter capsule development or alkaloid content significantly when applied during bud formation, but stimulated capsule size and alkaloid content when applied during capsule formation. Pretreating the plants with Ag⁺ (silver nitrate) did not reverse the ethephon effect. The results suggest that capsule maturation and alkaloid accumulation in P. somniferum are modified by ethylene, which is produced as a result of exogenous ethephon treatment.     

Maintenance of the diurnal petiolar movement by exogenous indole-3-acetic acid under day-night cycles in Mimosa pudica

Effects of plant hormones on the diurnal movement of the petiole of Mimosa pudica L. were examined under the conditions of day-night cycles. Surgical removal of the leaf at the middle of the petiole led to gradual loss of the movement. Aqueous solutions of indole-3-acetic acid (IAA) applied as a pulse each day 10 μl at (10⁻⁶−10⁻⁵ M ) or continuously (10⁻⁸−10⁻⁶ M ) to the cut end of the petiole maintained a diurnal movement that has the same phase of oscillation as that shown in the intact leaf. Pulse treatments given at different times of the day had no effect on the phase of the oscillation. Higher concentrations of the acid gave larger amplitudes. Other hormones such as gibberellic acid, kinetin and [R,S]-abscisic acid or 1-aminocyclopropane-1-carboxylic acid did not show diurnal movement-maintaining activities of IAA. Gibberellic acid disturbed the phase of the diurnal movements and kept the petiole elevated at very high positions. A possible action mechanism of IAA is discussed.     

Ca2+ acts synergistically with brassinosteroid and indole-3-acetic acid in stimulating ethylene production in etiolated mung bean hypocotyl segments

Brassinosteroid (BR) and indole-3-acetic acid (IAA) were used in combination with Ca²⁺ in order to determine if there was a synergistic effect in the stimulation of ethylene production in etiolated mung bean ( Vigna radiata L. Rwilez ev. Berken) hypocotyl segments. Ca²⁺ was found to act synergistically with BR. IAA or a combination of the two in promoting a stimulation in ethylene production. EDTA, which chelates Ca²⁺, greatly reduced the effectiveness of calcium salts in promoting ethylene production in the presene of either BR, IAA or a combination of the two. Neither K⁺, Mg²⁺ nor Mn²⁴ (chloride salts) acted synergistically with BR and IAA.     

Involvement of potassium ions in the action of various antineoplastic drugs on the growth of Saccharomyces cerevisiae

The involvement of potassium ions in the action of some antineoplastic drugs on the growth of Saccharomyces cerevisiae was studied by incubating yeast cells in the presence of drugs at various concentrations and KC1 at concentrations of 50 mmol 1^-1 and 100 mmol 1^-1. The presence of 6.25–50 μg m1^-1 amsacrine or melphalan alone in the culture medium had no significant effect on yeast growth. Addition of KC1 significantly increased the sensitivity to these drugs. On the contrary, incubation of yeast cells with KC1 had no effect on the cytotoxic action of doxorubicin, methotrexate or 5-fluorouracil.     

The cytotoxic and photodynamic inactivation of micro-organisms by Rose Bengal

Rose Bengal was cytotoxic to the following bacteria at the concentrations given in parentheses (highest concentrations of dye in mol/1 at which growth occurred on nutrient medium): Brochothrix thermosphacta and Deinococcus radiodurans (1 times 10^-6 or less); Streptococcus, Micrococcus, Staphylococcus, Bacillus, Arthrobacter and Kurthia spp. (1 times 10^-5–1 x 10^-4), and Pseudomonas spp. and Enterobacteriaceae (5 times 10^-3–1 x 10^-2 or greater). These organisms were killed rapidly when suspended in illuminated (170 μE/m²/s) solutions of Rose Bengal (1 times 10^-4 mol/1) providing oxygen was present. Singlet oxygen was identified as the lethal agent, because the rate of killing was increased by dissolving the dye in deuterium oxide while the organisms were protected against photoinactivation by L-histidine or crocetin. Yeasts from chilled foods were killed in illuminated solutions of Rose Bengal but a light intensity of 315 μE/m²/s was needed for a death rate comparable with that of bacteria. The yeasts present in a range of chilled meat and dairy products failed to form colonies on Rose Bengal (5 times 10^-5 mol/1) media exposed continuously to modest illumination (55–80 μE/m²/s).     

The effect of calcium concentration on the toxicity of copper, lead and zinc to yolk-sac fry of brown trout, Salmo trutta L., in soft, acid water

Yolk-sac fry of brown trout were exposed to three levels of single trace metals (Cu, 20,40,80 nmol 1^-1; Pb, 12·5,25,50 nmol 1^-1; Zn, 75,150,300 nmol 1^-1) typical of concentrations reported for acid soft waters, in flowing, artificial, soft water media maintained at pH 4·5 and [Ca] of 20 or 200 μmol 1^-1for 30 days.
Mortalities were high in fry subjected to all levels of the three trace metals at [Ca] 20 μmol 1^-1, with 80% of the total deaths occurring between days 11 and 15 of the experiment. 25% mortality occurred at low [Ca] and pH 4·5 in the absence of trace metals, with only one death recorded at [Ca] 200 μmol1^-1'(Cu, 80 nmol 1^-1). At high [Ca] all three levels of Cu and Pb impaired net Na and K uptake; Cu was the only metal to reduce the uptake of Ca. The Zn treatments had no significant effect on mineral uptake. Calcification of centra was reduced by all three Cu treatments at [Ca] 200 μmol 1^-1. The lowest Zn concentration (75 nmol 1^-1) was the only other treatment to impair skeletal development. In the absence of trace metals, low [Ca] significantly reduced Ca, Na and K uptake, skeletal calcification and dry mass at pH 4·5.
The deleterious effects of low Cu, Pb and Zn concentrations at low pH and low [Ca], and the ameliorative effect of higher ambient [Ca], are discussed in relation to fishery status in soft, acid waters.     

3,5-Dichlorophenoxyacetic acid as a growth retardant

Tomato seedlings, grown in the glasshouse, were sprayed with solutions of 3,5-dichlorophenoxyacetic acid as sodium salt at 2 times 10^-5, 4 times 10^-5 and 10^-4 M. The treated plants became dark-green, dwarfed, and compact. After 6–7 weeks normal growth was resumed. Measurements and analytical data on treated and control plants are presented.     

Effects of di-n-butyl phthalate on growth and photosynthesis in algae and on isolated organelles from higher plants

Di- n -butyl phthalate (DBF) is widely used as a plasticizer and has been found in all types of ecosystems. It inhibits growth and photosynthesis of green algae ( Chlorella emersonii CCAP strain 211/8 h and Selenastrum capricornutum CCAP strain 278/4) at concentrations higher than 10-⁵ M . The IC₅₀ value for CO₂-dependent oxygen evolution in algae was 3 × 10^-4M. The CO₂-reduction in isolated protoplasts prepared from barley ( Hordeum vulgare L. cv. Simba) was also inhibited by phthalate. The IC₅₀ value was 2 × 10^-4 M . The electron transport in isolated thylakoids prepared from spinach was inhibited with an IC₅₀ value of 3 × 10^-4 M . The IC₅₀ value for uncoupled electron transport extrapolated to zero chlorophyll concentration was 2.5 × 10^-5 M . The effect of di-n-butyl phthalate was localized to reactions in photosystem II. Di-n-butyl phthalate could thus be a pollutant which affects growth and photosynthesis of plants. The reported IC₅₀ values may be underestimated since di- n -butyl phthalate can attach to surfaces. The results are discussed in relation to observed effects of di- n -butyl phthalate on other organisms.     

Neuroendocrine stimulation of uterine gland protein synthesis in the tsetse fly, Glossina morsitans

ABSTRACT. The uterine gland of the tsetse fly Glossina morsitans morsitans Westw. synthesizes a secretion which nourishes the developing larva in the uterus. Aqueous extracts of the brain have been shown to stimulate the synthesis of the protein and amino acid components of this secretion from L- [U-¹⁴C]leucine by uterine gland tubules in vivo and in vitro. A linear dose response relationship was demonstrated in vitro with extract concentrations ranging from 1 × 10^-4 to 1 × 10^-2 brains μl^-1. The maximum response, a > 300% increase in the rate of protein and amino acid synthesis, was achieved with as little as 1 × 10^-2 brains μl^-1 The concentration of active factor(s) in the brain declined during a single interlarval period coincident with the period of release of secretion associated with larval growth. The stimulatory activity in brain extracts was destroyed by proteolytic enzymes indicating that it is probably a protein or peptide. Results suggest that the active factor(s) is a hormone responsible for the stimulation of uterine gland protein synthesis essential for larval nutrition.     

Effect of plant growth hormones and polyamines on ornithine decarboxylase activity during the germination of barley seeds

Gibberellic acid (GA₃) and β-indolylacetic acid (IAA), two of the well known growth hormones, induce four fold the activity of ornithine decarboxylase (ODC) during the germination of barley seeds ( Hordeum vulgare L. var. Beca). The optimal concentration for induction of ODC was 10^–5 M for GA₃ and 10^–3 M for IAA. When 10^–3 M of a polyamine, putrescine or spermidine, is added to the growth medium, ODC activity is significantly inhibited. This inhibition is due to the induction of a protein inhibitor of ODC (antizyme), whose apparent molecular weight is 16 000 ± 2 000 daltons. Addition of GA₃ to cultures which have been grown for 50 or 98 h in the presence of polyamines, abolishes the observed inhibition of ODC activity, while in the reverse experiment, addition of polyamines at 50 or 98 h does not affect the ODC activity induced by GA₃. Cadaverine, a physiological plant diamine, enhances ODC activity; whereas 1,8-diaminooctane (the alkyl analogue of spermidine) does not have any effect.     

2,4-Dichlorophenoxyacetic acid inhibition of potassium transport in barley seedlings

Growth, potassium uptake and translocation as well as transpiration rates were measured in intact low-salt barley seedlings ( Hordeum vulgare L. cv. Union) in the presence of different 2,4-D concentrations at pH 6.5. Growth was only affected at 10^-3 M .
Above 10^-7 M 2,4-D both uptake by the roots and transport to the shoots were inhibited. The inhibition at 10^-5 M remained constant for at least 24 h. Furthermore inhibition of uptake was measurable within 1 h. Excised roots and roots of intact plants showed the same uptake pattern.
It is suggested that the observed effects were caused by 2,4-D-induced changes in uptake and translocation systems in the roots. Pre-treatment with 10^-5 M 2,4-D had no effect upon subsequent potassium uptake. Transpiration was reduced within 1 h in 10^-4 or 10^-3 M 2,4-D, probably due to changes in water transport or root permeability.     

Effects of pollutants in fresh waters on European non-salmonid fish I: Non-metals

As part of a programme of acquiring data for preparing standards to safeguard European, nonsalmonid, freshwater fish from pollution, toxicity tests were carried out in hard, well-aerated water. Asymptotic median lethal concentrations (LC50s) of undissociated ammonia, cyanide, nitrite and phenol to one or more of three species were determined. The LC50s were as follows: to common carp 16mg1^-1 as NO₂–N; to perch 0.1 mg1^-1 as HCN; to roach 0.35 mg1^-1 as NH₃-N, 0-11mg1^-1 as HCN, 10.1 mg1^-1 asNO₂-Nand 10mg^-1 as phenol. In order to define these LC50s, exposure periods within the range 0.3 days (phenol) to 14 days (nitrite) were required. Comparisons are made with other data and the tentative water quality 'criteria' proposed by the European Inland Fisheries Advisory Commission.     

Mediation of sterol-induced calmodulin synthesis in Phaseolus vulgaris roots by Ca2+ and its possible relationship to plant growth regulators

Vitamin D₃ and stigmasterol have been previously shown to stimulate growth, Ca²⁺ fluxes and calmodulin synthesis in Phaseolus vulgaris roots. In this study, these sterols (10⁻⁹ M ) were shown to accelerate the incorporation of [³H]-thymidine into DNA in Phaseolus vulgaris (L. cv. Contraancha) root apices, similarly to a mixture of the mitogenic plant growth factors 2,4-dichlorophenoxyacetic acid and kinetin (4.6 μ M each). The effects of stigmasterol were blocked by flufenazine, a calmodulin antagonist. Analogously to stigmasterol, the plant hormones stimulated calmodulin synthesis as shown by double labeling of root proteins with [¹⁴C]-leucine and [³H]-leucine, respectively, followed by their separation on sodium dodecyl sulfate-po-lyacrylamide gels and a calmodulin affinity column, immunoblot analysis and cyclic AMP phosphodiesterase activation assays. The stimulation of root calmodulin formation by stigmasterol was abolished in the absence of Ca²⁺ in the incubation medium and was mimicked by the Ca²⁺ ionophore A–23187. The results suggest that the sterols, like plant mitogenic hormones, promote DNA synthesis, and that these compounds stimulate calmodulin synthesis as a consequence of their mitogenic activity. ^Ca2+ appears to mediate the action of the sterols.     

Bioelectrical reactions of Nitellopsis obtusa induced by indole-3-acetic acid

The complex of bioelectrical paramenters (membrane potential, membrane resistance and capacitance) of internodal cells of Nitellopsis obtusa was measured over a wide range of IAA concentration (10⁻¹⁰ to 10⁻⁴ M ) with two intracellular microelectrodes. Primary effects of IAA at a concentration as low as 10⁻¹⁰ M were observed. The optimum range of IAA action was from 10⁻⁹ to 10⁻⁶ M . The type of IAA-induced electroresponse depended on the initial level of membrane potential, which characterized the energetic state of the plasmalemma. In the energized state (ca −200 mV) N. obtusa cells appeared to have 3 typical reactions: hyperpolarization (membrane potential less than K⁺-equilibrium potential), depolarization (membrane potential higher than K⁺-potential) and absence of response at K⁺-electrochemical equilibrium. Membrane capacitance was found constant at 0.74 ± 0.05 μF cm⁻², but membrane resistance increased up to 50% independently of the sign of the electrogenic reaction. Increase of membrance capacitance and decrease of the membrane resistance was a feature of the de-energized state (ca −135 mV) and may be explained by lower viscosity of membrane lipids, which interacted with IAA. The complex of parameter, including cytoplasmic steaming taken as an indicator of energy supply, is discussed as indicating slow IAA penetration combined with a primary action of IAA on the plasmalemma receptor sites.     

Effect of pH, temperature and culture medium composition on the production of an extracellular cysteine proteinase by Micrococcus sp. INIA 528

Growth and proteinase production by Micrococcus sp. INIA 528 in a batch-operated laboratory fermentor were investigated, with trypticase soy broth as the basal medium for studies on optimum temperature, pH and medium composition. Maximum growth was recorded at 34°C and pH 715, whereas optimum temperature and pH for proteinase production were 31°C and pH 6.25. Maximum rate of enzyme production occurred during the late log and early stationary phases of growth. Addition of 5.0 g 1^-1 yeast extract, 1.0 g 1^-1 glucose, 1.0 g 1^-1 MgSO₄ or 1.0 g 1^-1 K₂HPO₄ to basal medium resulted in a lower enzyme yield, but supplementation of basal medium with 2.5 g 1^-1 (NH₄)₂SO₄ increased enzyme production by 45%. A high initial biomass added to fresh broth supplemented with 2.5 g 1^-1 (NH₄)₂SO₄ only increased enzyme activity by 19%, compared to the maximum enzyme activity achieved with the standard inoculum.     

Effect of herbicide diclofop-methyl on proton extrusion from Lolium multiflorum seedlings differing in resistance and in fungal endophyte (Neotyphodium sp.) infection

Lolium multiflorum (Italian ryegrass), an annual weed invading wheat and barley cropping systems, has evolved resistance to diclofop-methyl (DM) herbicide. Earlier studies on the mode of action of DM in susceptible L. multiflorum and L. rigidum populations have shown that herbicide promotes oxidative stress leading to senescence, a process reversible through the action of auxins. The disruption of cell membrane potential ( E _m ) appears to be correlated with DM phytotoxicity in susceptible populations, suggesting that the continuous H⁺ extrusion from plasmalemma to extracellular space is inhibited. L. multiflorum usually establishes a symbiotic relationship with fungal endophytes of the Neotyphodium genus. This fungus confers to host plants higher survival at sublethal dosages of DM, probably due to the production of auxinic compounds. Our goal was to characterize DM-resistant and DM-susceptible L. multiflorum populations infected (E+) and non-infected (E−) with endophytes, by studying the capacity of H⁺ bumping of plasmalemma of intact roots under DM selection. We correlated the effects of DM on H⁺ disruption with plant survival. DM inhibited acidification markedly more in susceptible than in resistant populations. Continued extrusion of H⁺ by DM-resistant cell membranes was positively related to plant survival and growth. There was no detectable difference in the capacity of bumping H⁺ between DM-susceptible E+ and E− seedlings, even though survival was higher in E+ plants. The basis for the differential response in H⁺ extrusion between resistant and susceptible populations of L. multiflorum is discussed.     

Flight responses of tsetse flies (Glossina) to octenol and acetone vapour in a wind-tunnel

Abstract. Female Glossina morsitans morsitans Westwood were video-recorded in a wind-tunnel as they entered, in crosswind flight, a broad plume of either octenol or acetone (two components of ox odour). Both odours produced upwind turning responses (in-flight anemotaxis) to a range of concentrations, with thresholds at around 10^-8mg1^-l for octenol and 10^-6mg1^-1 for acetone. Kinetic responses were unaffected by octenol at low concentrations, but flight speed was significantly reduced and sinuosity (^om^-1) and angular velocity (^os^-1) significantly increased by concentrations at or above those in ox breath; for acetone, these effects were apparent but inconsistently related to concentration. It is concluded that octenol and acetone vapour are used by tsetse flies to locate hosts by upwind anemotaxis, probably combined with kinetic responses. The behavioural basis for the 'repellency' of high octenol concentrations in the field is discussed in the context of the virtual loss of upwind anemotaxis to octenol at the highest concentration tested in the tunnel (30 × ox breath).     

Comparison of some decontamination methods and growth media for isolation of mycobacteria from northern brook waters

Two decontamination methods and five media were compared for the isolation of mycobacteria from brook waters of different physical, chemical and bacteriological characteristics. The decontaminants used were: 0.7 mol 1^-1 NaOH followed by 50 g 1^-1 oxalic acid and 0.9 mol 1^-1 H₂SO₄ combined with 0.5 g 1^-1 cycloheximide. The media compared were: Mycobacteria 7H11 agar with OADC enrichment (pH 6.6), glycerol egg (pH 6.5 and 5.5), and pyruvate egg (pH 6.5 and 5.5). All media contained cycloheximide, 0.5 g 1^-1. The NaOH—oxalic acid method generally resulted in lower contamination and higher isolation of mycobacteria than the H₂SO₄-cycloheximide method. With the NaOH—oxalic acid method, all five media were equal in positivity rates but contamination was a problem on Mycobacteria 7H11 agar. Of the four egg media tested, the highest positivity rate (92% of the samples) was obtained on the pyruvate modification (pH 6.5), and the highest mean colony count of mycobacteria (900 cfu 1^-1) on the glycerol modification (pH 6.5). Characteristics of water and sampling site had similar effects on the isolation frequencies of mycobacteria obtained by different combinations.