Physiological effects of long-term exposure to low and moderate concentrations of atmospheric NH3 on poplar leaves

Abstract. Poplar shoots ( Populus euramericana L.) obtained from cuttings were exposed for 6 or 8 weeks to NH₃ concentrations of 50 and 100 μgm⁻³ or filtered air in fumigation chambers. After this exposure the rates of NH₃ uptake, transpiration, CO₂ assimilation and respiration of leaves were measured using a leaf chamber. During the long-term exposure also modulated chlorophyll fluorescence measurements were carried out to obtain information about the photosynthetic performance of individual leaves. Both fluorescence and leaf chamber measurements showed a higher photosynthetic activity of leaves exposed to 100 μg NH₃ m⁻³. These leaves showed also a larger leaf conductance and a larger uptake rate of NH₃ than leaves exposed to 50 μg m⁻³ NH₃ or filtered air. The long-term NH₃ exposure did not induce an internal resistance against NH₃ transport in the leaf, nor did it affect the leaf cuticle. So, not only at a short time exposure, but also at a long-term exposure NH₃ uptake into leaves can be calculated from data on the boundary layer and stomatal resistance for H₂O and ambient NH₃-concentration. Furthermore, the NH₃ exposure had no effect on the relation between CO₂-assimilation and stomatal conductance, indicating that NH₃ in concentrations up to 100 μg m⁻³ has no direct effect on stomatal behaviour; for example, by affecting the guard or contiguous cells of the stomata.     

Anti-bacterial activity of synthetic N-heterocyclic oxidizing compounds

Synthetic chlorochromate derivatives of pyridine and quinoline were active in vitro against type cultures of Escherichia coli (ATCC 128), Staphylococcus aureus (ATCC 14775), Pseudomonas aeruginosa (ATCC 10145) and Bacillus subtilis (NCTC 8236). The minimum inhibitory concentrations (MIC) were 125–250 μg ml⁻¹ and 250–500 μg ml⁻¹ for pyridinium chlorochromate and quinolinium chlorochromate, respectively. An established derivative of quinoline (Perfloxacin) had an MIC of 125–250 μg ml⁻¹. The extinction time for 10⁵ cfu in broth was 90 min for pyridinium chlorochromate and 120 min for quinolinium chlorochromate, except for B. subtilis which survived up to about 180 min and 360 min. A combination of the two compounds produced an antagonistic effect. The 50% lethal dose (LD₅₀ toxicity) in mice was estimated at 76 μg g⁻¹ and 33 μg g⁻¹ body weight for the quinolinium and pyridinium chlorochromates. The compounds also exhibited some potential for suppressing a simulated staphylococcal infection in mice at the dosage levels of ca 22 μg g⁻¹ for pyridinium chlorochromate and 45 μg g⁻¹ for quinolinium chlorochromate.     

Insecticidal and synergistic effects of Majorana hortensis essential oil and some of its major constituents

The essential oil from leaves of Majorana hortensis Moench (Lamiaceae) was isolated by hydrodistillation with a yield of 1.6% (wt/wt). The insecticidal activity of the oil was evaluated against fourth instars of Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae) and adults of Aphis fabae L. (Hemiptera: Aphididae). The oil showed a remarkable toxic effect against S. littoralis in a topical application assay (LD₅₀ = 2.48 μg per larva) and in a residual film assay (LC₅₀ = 3.14 g/l). The oil of M. hortensis also exhibited a pronounced toxic effect against A. fabae adults with LC₅₀ values of 1.86 and 2.27 g/l in rapid dipping and residual film assays, respectively. Gas chromatography-mass spectrometry analyses of M. hortensis essential oils revealed the presence of 31 compounds and the main components were terpinen-4-ol (30.0%), γ-terpinene (11.3%), and trans -sabinene hydrate (10.8%). Repeated column chromatography of M. hortensis oil on silica gel led to the isolation of two major constituents, which were characterized based on ¹H-nuclear magnetic resonance and mass spectrometric data, as terpinen-4-ol and γ-terpinene. These two components were examined for their insecticidal and synergistic activities towards S. littoralis and A. fabae . Terpinen-4-ol and γ-terpinene exhibited a significant insecticidal activity against both insects, but γ-terpinene was more toxic than terpinen-4-ol. When tested in a binary mixture with the synthetic insecticides profenofos and methomyl, it was found that both compounds enhanced the insecticidal activity of these insecticides by two- to threefold. These results show that terpinen-4-ol and γ-terpinene have a synergistic effect on the insecticidal activities of synthetic insecticides profenofos and methomyl.     

Antibacterial Activity of Ambodryl and Benadryl

Of nine antihistamines screened for in vitro antibacterial activity, ambodryl (bromodiphenhydramine hydrochloride) and benadryl (diphenhydramine hydrochloride) were the most active. At 50 to 100 μ/ml concentrations these inhibited a large number of Gram negative and Gram positive bacteria in vitro , with ambodryl having a broader spectrum. In vivo tests showed that the compounds at single doses of 3 and 1.5 μg/g body weight protected mice against a challenge with a virulent strain (LD₅₀) of Salmonella typhimurium , and also significantly reduced the multiplication of this organism in the liver, spleen and blood of the protected animals in comparison with the unprotected controls.     

A developmental study of Glycine max cell and protoplast isolation in relation to leaf age and photosynthetic competence

Leaf mesophyll cells were isolated from developing first trifoliate leaves of Glycine max (L.) Merr cv. Fiskeby V using a mechanical isolation procedure combined with low speed centrifugation. Cell yields of 17 ± 1.7% were routinely obtained with 55–75% intactness, as assessed by staining techniques, fluorescence transients and the ability of cells to convert to protoplasts after enzyme treatment. Rates of leaf photosynthesis were maximal in 27-day-old plants [280 μmol O₂ evolved (mg chlorophyll)^-1h^-1], from which isolated cells and protoplasts gave rates of up to 140 μmol O₂ evolved (mg chlorophyll)^-1 h^-1. Results are discussed in relation to leaf development and cell status during the attainment of photosynthetic competence.     

Insecticide susceptibility and resistance of Blattella germanica (Blattaria: Blattellidae) in Seoul, Republic of Korea, 2007

The susceptibility of Blattella germanica (L.) in the Republic of Korea (ROK) to insecticides was evaluated under laboratory conditions using 12 insecticides currently used by the local public health centers and/or pest control operators in the ROK. The insecticides included seven pyrethroids and five organophosphates. Based on their LD₅₀ values, the order of susceptibility of B. germanica adults to the insecticides was chlorpyrifos-methyl, profenofos and chlorpyrifos with values of 0.07, 0.29 and 0.88 µg/♀, respectively. The least susceptibility was obtained with tetramethrin at LD₅₀ of 7.39 µg/♀. In the comparative resistance test, the resistance ratios (RR) of 12 insecticides were compared to each other using field-collected B. germanica adults in Seoul between 1993 and 2007. Blattella germanica demonstrated higher RRs to pyrethroids such as λ-cyhalothrin, and low RRs among the organophosphates. Among the pyrethroids, λ-cyhalothrin had the highest RRs of 111- and 129-fold differences at LD₅₀ and LD₉₀ values, respectively. Among the organophosphates, profenofos was observed to have the highest RRs of 4- and 15-fold differences at LD₅₀ and LD₉₀ values, respectively. However, there were no significant differences in susceptibility to tetramethrin, chlorpyrifos and fenitrothion. Blattella germanica was more susceptible to pyridafenthion showing a 0.7-fold difference in a resistance ratio (RRLD₅₀= LD₅₀ value of 2007/LD₅₀ value of 1993). Resistance ratio of tetramethrin was low, but susceptibility was also not high.     

Pathogenicity of different isolates of Vibrio harveyi in tiger prawn, Penaeus monodon

P.-C. LIU, K.-K. LEE AND S.-N. CHEN. 1996. The pathogenicity of six Vibrio harveyi strains in tiger prawn, Penaeus monodon , was studied, using both live bacteria and extracellular products (ECP). The organisms originally isolated from diseased penaeids were more virulent using both live bacteria and ECP (LD₅₀, 4.87–8.65 times 10⁴colony-forming units (cfu) and 1.20–1.51 μg protein g^-1body weight) than the two reference strains originally isolated from either sea water (ATCC 25919; LD₅₀, 3.18 times 10⁶cfu and 2.70 μg protein g^-1body weight) or diseased Talorchestia sp. (ATCC 14126, 0.418 times 10⁶cfu and 2.34 μg protein g^-1body weight). Each strain was reisolated from the haemolymph and the hepatopancreas of moribund prawns following each bacterial challenge. Both the live bacteria and the ECPs of the penaeid isolates exhibited stronger proteolytic (caseinase), phospholipase and haemolytic activities than those of the reference strains. These results indicate that there are differences between penaeid and non-penaeid isolates of V. harveyi in pathogenicity and reveal that proteases, phospholipases, haemolysins or exotoxins might play leading roles in the pathogenicity of V. harveyi in the tiger prawn, Penaeus monodon .     

Direct and indirect effects of Cd2+ on photosynthesis in sugar beet (Beta vulgaris)

Sugar-beet plants ( Beta vulgaris L. cv. Monohill) were cultivated for 4 weeks in a complete nutrient solution. Indirect effects of cadmium were studied by adding 5, 10 or 20 μ M CdCl₂ to the culture medium while direct effects were determined by adding 1, 5, 20, 50 or 2 000 μ M CdCl₂ to the assay media. The photosynthetic properties were characterized by measurement of CO₂ fixation in intact plants, fluorescence emission by intact leaves and isolated chloroplasts, photosystem (PS) I and PSII mediated electron transport of isolated chloroplasts, and CO₂-dependent O₂ evolution by protoplasts. When directly applied to isolated leaves, protoplasts and chloroplasts. Cd²⁺ impeded CO₂ fixation without affecting the rates of electron transport of PSI or PSII or the rate of dark respiration. When Cd²⁺ was applied through the culture medium the capacity for, and the maximal quantum yield of CO₂ assimilation by intact plants both decreased. This was associated with: (1) decreased total as well as effective chlorophyll content (PSII antennae size), (2) decreased coupling of electron transport in isolated chloroplasts, (3) perturbed carbon reduction cycle as indicated by fluorescence measurements. Also, protoplasts isolated from leaves of Cd²⁺-cultivated plants showed an increased rate of dark respiration.     

Pathogenicity of live bacteria and extracellular products of motile Aeromonas isolated from eels

The pathogenic activities in vitro and in vivo of live bacteria and extracellular products (ECP) of 24 motile Aeromonas strains were investigated. Most Aer. hydrophila and Aer. jandaei isolates were pathogenic for eels (LD₅₀ 10^5·4-10^7·6 cfu fish^-1) but no Aer. sobria , Aer. caviae and Aer. allosaccharophila caused mortality in eels at doses of > 10^8·4 cfu fish^-1. Of these Aeromonas strains, Aer. hydrophila and Aer. jandaei in particular produced elastases and haemolysins against fish erythrocytes. ECP from Aer. hydrophila and Aer. jandaei caused degenerative changes in fish cell lines and were strongly toxic for eels (LD⁵⁰ 1·0–3·2 μg (g fish)^-1) reproducing the symptoms associated with natural disease. ECP from non-pathogenic species were inactive on fish cell lines as well as being poorly lethal for eels (LD⁵⁰ > 9·2 μg (g fish)^-1). All these biological activities of Aeromonas ECP were lost after heat treatment. These findings indicate differences between pathogenic and non-pathogenic Aeromonas species with respect to the expression of virulence factors, and show that elastases, haemolysins and exotoxins play a leading role in the pathogenicity of motile Aeromonas for eels.     

Responses of apple leaf stomata to environmental factors

Abstract. Stomatal conductances ( g _s) were measured on the leaves of 3–4 year old Golden Delicious trees and of seedlings of two other cultivars. Measurements were made on container grown trees in the field with a diffusion porometer in 1975 and 1976, and in controlled conditions in a leaf chamber in the laboratory in 1976. Stomatal densities in the Golden Delicious leaves were assessed from scanning electron micrographs. Stomatal density on extension shoot leaves was higher than on other leaf types after June.
The response to irradiance shown by both the porometer and the leaf chamber results could be described by a rectangular hyperbola: where g _max is maximum conductance and β indicates the sensitivity of g_s to photon influx density ( Q _p). The values of β were in the range 60–90 μmol m⁻² s⁻¹.
There was no evidence that apple stomata are sensitive to temperature per se, but g _s was reduced by increasing leaf to air vapour pressure deficits ( D ). There was a linear relationship between g _s and D which was not attributable to feed-back to leaf water potential (ψ_L) as the latter did not affect g _s until a threshold of about −2.0 to −2.5 MPa was reached. Conductance generally declined with increasing ambient CO₂ concentration.     

Toxicity of organotins towards cyanobacterial photosynthesis and nitrogen fixation

Abstract Inhibition of photosynthesis by a range of organotin compounds in Plectonema boryanum was concentration-dependent and decreased in the order tributyltin (Bu₃SnCl) > tripropyltin (Pr₃SnCl) ≥ dibutyltin (Bu₂SnCl₂) ≥ triphenyltin (Ph₃SnCl) > triethyltin (Et₃SnCl) > trimethyltin (Me₃SnCl) > monobutyltin (BuSnCl₃). IC₅₀ values were determined for the most toxic organotin species and varied from approximately 1.2 μM for Bu₃SnCl to approximately 13 μM for Ph₃SnCl. A similar order of inhibition of photosynthesis was observed in Anabaena cylindrica , although here IC₅₀ values were slightly lower (e.g. approximately 1 μM for Bu₃SnCl and 5 μM for Ph₃SnCl).Nitrogenase activity was generally more sensitive to inhibition by organotin compounds than photosynthesis in A. cylindrica and this was particularlyy evident for Bu₂SnCl₂; approximate IC₅₀ values for Bu₂SnCl₂ were 3 and 9 μM, as estimated by nitrogenase activity and photosynthesis, respectively. These results indicate that organotin compounds have the potential to inhibit cyanobacterial metabolism in aquatic systems.     

Interactions between hydrogen cyanide, gibberellin, abscisic acid and red light in germination of lettuce seeds

Germination of lettuce ( Lactuce sativa L. cy. Grand Rapids) seeds was promoted by red light and by pulse treatments with gibbercllie acid (GA₃) or hydrogen cyanide, whereas it was inhibited by short exposure of seeds to absusic acid (ABA). The eflects of unsalLirating red light and of 10 μ M GA₃ on lettuce germination were completely reversed the effect of ABA (100 μ M ). In contrast, hydrogen cyanide did not reverse the effect of 100 μ M ABA and only partly eliminated the effect of 10μ M ABA, independently of the sequence of treatments. Possible interactions between HCN GA₃, ABA and red light were discussed. It was concluded thai light GA₃ and HCN affect different mechanisms involved in lettuce germination: ABA counteracts the stimulatory action of all these faclors. being the most effective against cvanide Additional key words - Lactuca sativa, pholodormancy, phylohormoncs.     

Influence of phytohormones and other effectors on proton extrusion by isolated protoplasts from rape leaves

The roles of phytohormones and fusicoccin in H⁺ extrusion by isolated protoplasts from rape leaves ( Brassica napus L. cv. Belinda) were investigated and compared to results obtained with leaf segments of the same plants. Net H⁺ release by protoplasts, which was at least partly due to ATPase activity, was enhanced by 10 μ M indole-3-acetic acid and reduced by 20 μ M abscisic acid, whereas fusicoccin (10 μ M ), brassinosteroid (3 μ M ), kinetin (20 μ M ) and gibberellic acid (10 μ M ) had no effect. Hormone effects and H⁺ release were not detectable with leaf segments from the same plants. However, using field-grown plants, indole-3-acetic acid and especially fusicoccin stimulated the acidification of the external medium by leaf segments. Hormonecontrolled H⁺ release by leaf cells is interpreted as the first step in acid-triggered and turgor-regulated cell growth.     

Nitrogen nutrition of C3 plants at elevated atmospheric CO2 concentrations

The atmospheric CO₂ concentration has risen from the preindustrial level of approximately 290 μl l⁻¹ to more than 350 μl l⁻¹ in 1993. The current rate of rise is such that concentrations of 420 μl l⁻¹ are expected in the next 20 years. For C₃ plants, higher CO₂ levels favour the photosynthetic carbon reduction cycle over the photorespiratory cycle, resulting in higher rates of carbohydrate production and plant productivity. The change in balance between the two photosynthetic cycles appears to alter nitrogen and carbon metabolism in the leaf, possibly causing decreases in nitrogen concentrations in the leaf. This may result from increases in the concentration of storage carbohydrates of high molecular weight (soluble or insoluble) and/or changes in distribution of protein or other nitrogen containing compounds. Uptake of nitrogen may also be reduced at high CO₂ due to lower transpiration rates. Decreases in foliar nitrogen levels have important implications for production of crops such as wheat, because fertilizer management is often based on leaf chemical analysis, using standards estimated when the CO₂ levels were considerably lower. These standards will need to be re-evaluated as the CO₂ concentration continues to rise. Lower levels of leaf nitrogen will also have implications for the quality of wheat grain produced, because it is likely that less nitrogen would be retranslocated during grain filling.     

Host plant preference and the influence of different cabbage cultivars on the toxicity of abamectin and cypermethrin against Plutella xylostella Lepidoptera: Plutellidae

The toxicity of avermectin B, (abamectin) and cypermethrin was determined against fourth instar larvae of Plutella xylostella L. reared on three cabbage cultivars which differed in their suitability as host plants. Cabbage cultivars were assessed as hosts for P. xylostella on the basis of larval and pupal weight and adult fecundity. Larvae reared on the best host, the cabbage cv. Offenham Flower of Spring were significantly (P > 0.01) less sensitive to topically-applied abamectin (4.7-fold at LD₅₀) or cypermethrin (2.3-fold) when compared with larvae reared on the intermediate host, the Savoy cabbage cv. Aquarius F1. Larvae reared on Offenham Flower of Spring were also significantly (P > 0.01) less sensitive (4.5-fold) to topically-applied abamectin compared with larvae reared on the poorest host tested, the cabbage cv. Minicole Fl. In contrast, the residual/ingestion toxicity of abamectin against fourth instars was significantly (P > 0.01) greater (2.5-fold at LC₅₀) on Offenham Flower of Spring than on Minicole F1. The results are discussed in terms of larval weight and larval feeding rates on the different cabbage cultivars.     

Larvicidal toxicity of Japanese Bacillus thuringiensis against the mosquito Anopheles stephensi

Japanese isolates of Bacillus thuringiensis were screened for larvicidal activity against the mosquito Anopheles stephensi , the urban malaria vector of the Indian subcontinent. Among more than 30 strains identified, larvicidal activity causing >80% mortality in 72 h was demonstrated for 41/1449 (2.8%) isolates. The majority of strains and isolates (97.2%) exhibited little or no larvicidal activity. Anopheles -active strains belonged to more than 12 H serotypes, especially H3ade (serovar fukuokaensis ) and H44 (serovar higo ). SDS-PAGE profiles of inclusion proteins showed 4 distinct types among 6 active strains examined. The most active Japanese isolates were H20 strain 89-T-34-14 (LC₅₀ 4.4 μg/ml) and H44 serovar higo strain 74-E-45-24 (LC₅₀ 7.6 μg/ml), respectively, 13-fold and 23-fold less active than the international standard H14 serovar israelensis (LC₅₀ 0.33 μg/ml).     

Seasonal changes in some photosynthetic properties of Ceratonia siliqua (carob tree) leaves under natural conditions

Rates of photosynthesis and leaf conductance of the leaves of carob trees ( Ceratonia siliqua L.) growing in natural conditions were measured during the course of the seasons to define the effects of the main climatic factors limiting growth in the region: temperature during the winter and water in the summer. The highest photosynthetic rates were measured in spring and autumn and could reach 25 μmol m₋₂ s₋₁ with optimal temperature and available water. Due to lower temperatures (4 to 6°C in the night) these values were frequently around 15 μmol m₋₂ s₋₁ during winter, but the strongest depression was due to prolonged drought in summer. However a reduction in photosynthesis rate down to 5 μmol m₋₂ s₋₁ occurred only after depletion of all the available water in the soil layer up to a depth of 50 cm. In the end of the summer, leaf conductance and water potential were in the order of 20 mmol m₋₂ s₋₁ and −3 MPa respectively. Compared to other trees that make up the Mediterranean sclerophyll forest, the photosynthetic activity of carob is high, and the tree tolerates a considerable depletion of soil water.     

Assimilate relations in source and sink leaves during acclimation to a CO2-enriched atmosphere

Evidence from previous studies suggested that adjustments in assimilate formation and partitioning in leaves might occur over time when plants are exposed to enriched atmospheric CO₂. We examined assimilate relations of source (primary unifoliolate) and developing sink (second mainstem trifoliolate) leaves of soybean [ Glycine max (L.) Merr. cv. Lee] plants for 12 days after transfer from a control (350 μl l⁻¹) to a high (700 μ l⁻¹) CO₂ environment. Similar responses were evident in the two leaf types. Net CO₂ exchange rate (CER) immediately increased and remained elevated in high CO₂. Initially, the additional assimilate at high CO₂ levels in the light and was utilized in the subsequent dark period. After approximately 7 days, assimilate export in the light began to increase and by 12 days reached rates 3 to 5 times that of the control. In the developing sink leaf, high rates of export in the light occurred as the leaf approached full expansion. The results indicate that a specific acclimation process occurs in source leaves which increases the capacity for assimilate export in the light phase of the diurnal cycle as plants adjust to enriched CO₂ and a more rapid growth rate.     

Effects of low concentrations of O3, leaf age and water stress on leaf diffusive conductance and water use efficiency in soybean

Ozone, leaf age and water stress each affected leaf conductance in soybean [ Glycine max (L.) Merr. Hodgson], but there were no interactions among these factors. Exposure to increased concentrations of O₃ (0.01, 0.05, 0.09. and 0.13 μl l⁻¹) resulted in linear declines in abaxial and adaxial conductances in leaves of all ages. There were no differences in relative response to O₃ between the two leaf surfaces. For well-watered plants, water use efficiency also decreased with exposure to increased O₃ concentrations (water-stressed plants were not tested). Abaxial conductance increased as leaves aged from 4 to 10 days and then declined with further aging. Adaxial conductance decreased with all increases in leaf age beyond 4 days, and the ratio of abaxial/adaxial conductance increased continuously throughout the leaf lifespan. During water-stress cycles (water withheld for 2–3 days) leaves of water-stressed plants had lower conductances than those from well-watered plants, and there was no difference in relative response between abaxial and adaxial stomata.