Flooding, gas exchange and hydraulic root conductivity of highbush blueberry

Highbush blueberry plants ( Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO₂ and O₂ concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO₂ levels on carbon assimilation less for flooded than unflooded plants after short-(i-2 days), intermediate-(10–14 days) and long-term (35–40 days) flooding. A reduction in O₂ levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO₂ fixed (mol CO₂)⁻¹. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O₂, averaging 0.005 mol CO₂ fixed (mol CO₂)⁻¹. Apparent quantum yield decreased from 2.2 × 10⁻¹ mol of CO₂ fixed (mol light)⁻¹ for unflooded plants to 2.0 × 10⁻³ and 9.0 × 10⁻⁴ for intermediate- and long-term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf.     

Mechanism of phosphorus-induced zinc deficiency in cotton. III. Changes in physiological availability of zinc in plants Is mail

The effect of varied supply of P (2.5× 10⁻⁵ to 6× 10⁻⁴ M) and Zn (0 to 10⁻⁶ M) on uptake and concentrations of P and Zn was studied in cotton ( Gossypium hirsutum L. cv. Deltapine 15/21) grown in nutrient solution under controlled environmental conditions. At a given Zn supply, increasing levels of P had no significant effect on the concentrations of total Zn in plants. However, increasing levels of P induced or enhanced visual Zn deficiency symptoms when the Zn concentration in the nutrient solution was low. The concentrations of water-soluble Zn in roots and shoots constituted 60% of the total Zn concentrations for plants grown with low P and 30% for plants grown with high P. The concentration of water-soluble Zn in leaves, but not total Zn, was closely correlated with visual Zn deficiency symptoms, levels of chlorophyll, super oxide dismutase and membrane permeability. The critical deficiency concentration of water-soluble Zn in cotton leaves was in the range of 6 to 7 μg (g dry weight)⁻¹ or about 1.0 μg (g fresh weight)⁻¹. The results show that high P concentrations in plant tissue decrease the physiological availability of Zn. Water-soluble Zn in the tissue appears to be a suitable indicator for Zn nutritional status in general and phosphorus-induced Zn deficiency in particular. Also in field-grown orange trees (Citrus sinensis) visual Zn deficiency symptoms in leaves were closely related to the concentration of water-soluble Zn.     

The effect of exposure to enhanced UV-B radiation on the penetration of monochromatic and polychromatic UV-B radiation in leaves of Brassica napus

Using quartz optical fibres, penetration of both monochromatic (310 nm) and polychromatic UV-B (280–320 nm) radiation in leaves of Brassica napus L. (cv. Ceres) was measured. Plants were grown under either visible light (750 μmol m⁻² s⁻¹ photosynthetically active radiation) or with the addition of 8. 9 KJ m⁻² day⁻¹ biologically effective UV-B (UV-B_BE) radiation. Results showed that of the 310 nm radiation that penetreated the leaf, 90% was within the intial one third of the leaf with high attenuation in the leaf epidermis, especially in UV-treated plants. Polychromatic UV-B radiation, relative to incident radiation, showed a relatively uniform spectral distribution within the leaf, except for collimated radiation. Over 30% of the UV-screening pigments in the leaf, including flavonoids, were found in the adaxial epidermal layer, making this layer less transparent to UV-B radiation than the abaxial epidermis, which contained less than 12% of the UV-screening pigments. UV-screening pigments increased by 20% in UV-treated leaves relative to control leaves. Densely arranged epicuticular wax on the adaxial leaf surface of UV-treated plants may have further decreased penetration of UV-B radiation by reflectance. An increased leaf thickness, and decreases in leaf area and leaf dry weight were also found for UV-treated plants.     

Respiratory energy requirements and rate of protein turnover in vivo determined by the use of an inhibitor of protein synthesis and a probe to assess its effect

Protein turnover is generally regarded as a major maintenance process, but experimental evidence to support this contention is scarce. Here we quantify the component of dark respiration rate associated with overall protein turnover of tissues in vivo. The effect of an inhibitor of cytosolic protein synthesis (cycloheximide, CHM) on dark respiration was tested on a cell suspension from potato ( Solanum tuberosum L.) and quantified on leaf discs of expanding and full-grown primary leaves of bean ( Phaseolus vulgaris L.). The in vivo effect of CHM on protein biosynthesis was assessed by monitoring the inhibition of the induction of the ethylene-forming enzyme (EFE) activity. The present method yields the energy costs of turnover of the total pool of proteins irrespective of their individual turnover rates. Average turnover rates were derived from the respiratory costs and the specific costs for turnover.
Inhibition of respiration by CHM was readily detectable in growing-cell suspensions and discs of expanding leaves, The derived respiratory costs of protein turnover in expanding leaves were maximally 17–37% of total respiration. Turnover costs in full-grown primary leaves of bean amounted to 17–21% of total dark respiration. The maximum degradation constants (i.e. K_d-values) derived for growing and full-grown leaves were up to 2.42 × 10⁻⁶ and 1.12 × l0⁻⁶ s⁻¹, respectively.     

Apoplastic mobility of sucrose in storage parenchyma of sugar beet

The apoplastic movement of sucrose through storage parenchyma discs (2.4 mm thick) from roots of sugar beet ( Beta vulgaris var. altissima ) was investigated in order to evaluate the suitability of the apoplast for transcellular sugar transport. The sucrose permeability of the discs (P = 5.7 × 10⁻⁸ cm s⁻¹ at 25°C) was more than two orders of magnitude lower than that of an equally thick layer of unstirred water. This is due to the small volume fraction of free space (3.1%) and the decreased diffusion coefficient D of sucrose in the cell walls. The effective diffusion coefficient of the apoplast (6 to 9 × 10⁻⁷ cm² s⁻¹ at 25°C) was determined independently of the cross sectional area of free space by treating the time course of fluxes according to Fick's second law. The high diffusion resistance of the apoplast has to be considered in models of native parenchyma transport.     

A light intensity threshold for schooling in the Atlantic mackerel, Scomber scombrus

The schooling behaviour of Atlantic mackerel was studied in a large tank at different light intensities in the range 12.6–1.8 × 10⁻¹⁰μEs⁻¹ m⁻². Variable light intensity was produced by accurately controlling the current to a green light-emitting diode (LED) 3 m above the experimental tank. Under high light levels (1.8 × 10⁻⁶μEs⁻¹ m⁻²) mackerel always formed a single school, whereas at lower levels (1.8 × 10⁻⁸μEs⁻¹ m⁻²) they swam as individuals. At light levels down to 1.0 × 10⁻⁶μEs⁻¹ m⁻² the mean nearest neighbour distance in a school remained relatively constant (0.3–0.9 body lengths), and individual mackerel swam along a path which deviated from the position of their nearest neighbours by less than 14°. As light dropped below 1.8 × 10⁻⁷μEs⁻¹ m⁻², both nearest neighbour distance and heading angle between nearest neighbours increased, with mean values of 1–1.8 body lengths and 23–92°, respectively, at 1.8 × 10⁻⁹μEs⁻¹ m⁻². The results are discussed in terms of ambient light conditions in the sea.     

Sperm structure and motility of the freshwater teleost Cottus gobio

When motility of spermatozoa of Cottos gobio was initiated with distilled water, the motility rate decreased to 0% within 1 min, and significant signs of osmotic alterations were observed at the end of the motility period. By contrast, in 50 mmol 1⁻¹ NaCl solution, the motility rate persisted for 120–140 min. In both distilled water and in 50 mmol 1⁻¹ NaCl solution, the main swimming type of spermatozoa was linear motion during the whole motility period. The initial swimming velocity (50.0 ± 2.1 μm s⁻¹) measured 10 s after motility initiation was similar in both distilled water and in 50 mmol 1⁻¹ NaCl solution. In distilled water, the velocity decreased to <20 μm s⁻¹ (locally motile) during the first minute of the motility phase. In 50 mmol 1⁻¹ NaCl solutions, it remained at a constant level during the first 60 min of the motility period, but then started to decrease to <20 μm s⁻¹ after 120 min. When 5 mmol 1⁻¹ potassium cyanide, antimycin or atractyloside was added to the 50 mmol 1⁻¹ NaCl solution, the motility period was reduced to ≤2min. Ten millimoles per litre 2-deoxy-D-glucose, malonate or a mixture of 5 mmol 1⁻¹ atractyloside and 5 mmol 1⁻¹ carnithine did not effect the duration of the motility period. This indicates that sperm energy metabolism depends mainly on respiration rate and fatty acid metabolism.     

Permeability of the Chara cell membrane for ethylene glycol, glycerol, meso-erythritol, xylitol and mannitol

The permeability of internodal cells of Chara australis R. Brown for polyol molecules was determined by using a turgor balance to measure the increase in the osmotic pressure of an internodal cell incubated in artificial pond water containing one of the polyol compounds tested. The permeabilities for ethylene glycol, glycerol, meso -erythritol, xylitol and mannitol were (4. 39 ± 0. 52) × 10⁻⁹, (1. 49 ± 0. 40) × 10¹⁰, (4. 92 ± 0. 27) × 10⁻¹⁰ (9. 9 ± 3. 4) × 10¹¹ and (7. 6 ± 4. 8) × 10⁻¹² m s⁻³, respectively. The permeability for glycerol was slightly smaller than that for meso -erythritol, whose molecular weight is larger than that of glycerol in this homologous series: but the reason for this is not clear.     

The composition and function of thylakoid membranes from pea plants grown under white or green light with or without far-red light

Pea plants ( Pisum sativum L. ev. Greenfeast) were grown for 2 to 3 weeks in while (˜ 50 μmol photons m⁻² s⁻¹; 400–700 nm) or green (˜ 30 μmol photons m⁻² s ⁻¹ 400–700 nm) light (16 h day/8 h night), with or without far-red light. Supplementary far-red light decreased leaf area and increased internodal length in both white and green light, demonstrating that phytochrome influenced leaf size and plant growth. However, there was no effect of far-red light on chlorophyll a /chlorophyll b ratios, chlorophyll-protein composition, the stoichiometry of electron transport complexes or photosynthetic function of isolated thylakoids. These results suggest that phytochrome is ineffective in modulating the composition and function of thylakoids in pea plants grown at low irradiance. One possible explanation of the ineffectiveness of phytochrome on thylakoids is discussed in terms of the drastic attenuation of red relative to far-red light in green tissue.     

Chlorsulfuron influence on garden pea reproduction

The influence of chlorsulfuron on the reproduction of green pea ( Pisum sativum ) was examined by exposing plants at 3 different stages of development to 3 different exposure levels (46, 92, and 180 mg ha⁻¹; corresponding to 2 × 10⁻³, 4 × 10⁻³, and 8 × 10⁻³ of the recommended field application rates for small grain crops). Reproduction was only influenced by the two higher rates. The most susceptible stage of development was when plants possessed 6 expanded leaves and one visible flower bud. At that stage, an application rate of 180 mg ha⁻¹ (0.8% of the recommended field rate) reduced the seed yield of treated plants to 1% of that of the control plants without severely altering the height or appearance of mature plants. When correspondingly low application rates of atrazine. glyphosate, and 2.4-D were administered at this same developmental stage there were no effects on either growth or reproduction. Thus, chlorsulfuron had an influence on plant reproduction that was not produced by other herbicides administered at low levels.     

Water-relation parameters of giant and normal cells of Capsicum annuum pericarp

Abstract. Measurements of the water-relation parameters of the giant subepidermal cells (volume, V = 0.119 to 1.658 mm³; = 0.53±0.35 mm³, SD, n = 23) and the smaller mesocarp parenchyma cells ( V = 0.10 to 0.79×10⁻³ mm³; = 0.36±0.27×10⁻³ mm³, SD, n = 6) of the inner pericarp surface of Capsicum annuum L. were made using the Jülich pressure probe. The volumetric elastic modulus ɛ for the large cells was between 1.5 and 27 MPa for a pressure range of 0.09 to 0.41 MPa. For the small cells ɛ was 0.1 to 0.6 MPa for a pressure range of 0.22 to 0.39 MPa. The turgor pressure P , the half-time of water exchange T _1/2, and the hydraulic conductivity L _p were as follows, with SD and number of replicates: large cells, P = 0.27±0.06 MPa (23), T _1/2=2.7±2.2 s (46), L _p=5.8±3.7 pm s⁻¹ Pa⁻ (46); small cells, P = 0.33±0.07 MPa (6), T _1/2= 33±10s (12), L _p=0.21±0.07 pm s⁻¹ Pa⁻¹ (12). The determination of these basic water-relation parameters is considered as a prerequisite for future ecotoxicological and phytopathological studies. The differences between the large and the small cells are discussed in relation to a desirable biophysical definition of succulence. Further, for the large cells a pressure and volume dependence of ɛ was demonstrated.     

Stability and conjugal transfer kinetics of a TOL plasmid in Pseudomonas aeruginosa PAO 1162

Abstract Batch mating experiments were employed to study the kinetics of the conjugal transfer of a TOL plasmid, using the transconjugant strain Pseudomonas aeruginosa PAO 1162 (TOL) as the plasmid donor and Pseudomonas putida PB 2442 and Pseudomonas aeruginosa PAO 1162N as the plasmid recipients. Transfer rates from PAO 1162 (TOL) to PAO 1162N and PB 2442 measured for exponentially grown PAO 1162 (TOL) were 1.81 × 10⁻¹⁴ (standard error (S.E.) 1.25 × 10⁻¹⁵) ml·cell⁻¹min⁻¹ and 3.32 × 10⁻¹³ (S.E. 4.42 × 10⁻¹⁴) ml·cell⁻¹min⁻¹, respectively. The instability of the TOL plasmid in PAO 1162 (TOL) was evaluated under conditions that were non-selective for maintenance of the TOL catabolic functions. The measured rates of instability were 6.7 10⁻⁶ to 8.3 10⁻⁶ min⁻¹, and the loss of the catabolic functions was mainly caused by structural instability of the plasmid.     

The effect of turbidity and illumination on the reaction distance and search time of the marine planktivore Gobiusculus flavescens

Both reduced illumination and increased turbidity caused a significant reduction in reaction distance of Gobiusculus flavescens . The longest reaction distance, 18.9 cm for larger prey (Calanus finmarchicus) , occurred at a light level of 80 μmol m ⁻² s ⁻¹ compared to 12.9 cm for a smaller prey (Acartia clausi) at 8 μmol m⁻² s⁻¹. Above a light saturation level of 10 μmol m⁻² s⁻¹, additional light had little influence on reaction distance. In the turbidity experiments, the longest reaction distances were measured at turbidity levels of 10–20 JTU. Prey size influenced reaction distance at all tested light levels. Search time was influenced by prey size only at low illumination. With increasing turbidity, reaction distance to a group of prey was longer than to one prey.     

The formation of migratory ripples in a mixed species bacterial biofilm growing in turbulent flow

Mixed-species biofilms, consisting of Klebsiella pneumoniae , Pseudomonas aeruginosa , Pseudomonas fluorescens and Stenotrophomonas maltophilia , were grown in glass flow cells under either laminar or turbulent flow. The biofilms grown in laminar flow consisted of roughly circular-shaped microcolonies separated by water channels. In contrast, biofilm microcolonies grown in turbulent flow were elongated in the downstream direction, forming filamentous 'streamers'. Moreover, biofilms growing in turbulent flow developed extensive patches of ripple-like structures between 9 and 13 days of growth. Using time-lapse microscopic imaging, we discovered that the biofilm ripples migrated downstream. The morphology and the migration velocity of the ripples varied with short-term changes in the bulk liquid flow velocity. The ripples had a maximum migration velocity of 800 μm h⁻¹ (2.2 × 10⁻⁷ m s⁻¹) when the liquid flow velocity was 0.5 m s⁻¹ (Reynolds number = 1800). This work challenges the commonly held assumption that biofilm structures remain at the same location on a surface until they eventually detach.     

Latitudinal cline of requirement for far‐red light for the photoperiodic control of budset and extension growth in Picea abies (Norway spruce)

To test for the effects of far‐red light on preventing budset in Picea abies , seedlings of six populations originating from latitudes between 67°N and 47°N were grown for 4–8 weeks in continuous incandescent (metal halogen) light at 300 µmol m⁻² s⁻¹ and 20°C and then transferred, at the same temperature, to a daily regime of 8 h incandescent light (300 µmol m⁻² s⁻¹) followed by 16 h cool white fluorescent light (40 µmol m⁻² s⁻¹). (Cool white lamps are deficient in far‐red light, with a R/FR ratio of 7.5 compared with 2.0 for the incandescent lamps.) All the seedlings from 67° and 80% of those from 64° stopped extension growth and set terminal buds within 28 days of the change of regime. The seedlings from 61° and further south continued growing, as did control seedlings from 67° grown as above but with incandescent light at 20 µmol m⁻² s⁻¹ replacing cool white illumination. To distinguish between a clinal and ecotypic pattern of variation, the interval between 64° and 59° was investigated by growing populations originating from that area in the same regimes as before. After 28 days in the cool white day‐extension regime, the percentage budset was 86 for the population from 64°, 0 for the population from 59° and 25–50 for the intermediate populations; i.e. the populations showed a clinal variation in requirement for far‐red light according to latitude. Thus northern populations of Picea abies appear to behave as 'light‐dominant' plants for the photoperiodic control of extension growth and budset, whereas the more southern populations behave as 'dark‐dominant' plants.     

Chronic Ethanol Reduces Immunologically Detectable Gqα/11α in NG108–15 Cells

Abstract: The amyloid protein (βA₄) is found in the CNS of patients with Alzheimer's disease; however, the pathogenic role of this protein is not known. In the present study, a peptide fragment of βA₄βA₄ 25–35; Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-NH₂), which contains the conserved C-terminal sequence of substance P (X-Gly-Leu-Met-NH₂), and the neuropeptide substance P (SP) were examined for their ability to modulate nicotine-evoked secretion from cultured bovine adrenal chromaffin cells. Secretion of the released endogenous catecholamines was monitored by electrochemical detection after separation by HPLC. Secretion induced by 10⁻⁵ M nicotine was inhibited by SP and βA₄ 25–35. The IC₅₀ of SP and βA₄ 25–35 was 3 × 10⁻⁶ and 3 × 10⁻⁵ M , respectively. SP and βA₄ 25–35 both protected against nicotinic receptor desensitization. However, βA₄ 25–35 was ∼ 10-fold less effective than SP in its protective effect. The present work shows that βA₄ 25–35 can mimic the modulatory actions of SP on the nicotinic response of cultured bovine chromaffin cells, i.e., inhibition of the nicotinic response and protection against nicotinic desensitization. These modulatory actions may be associated with changes in nicotinic receptor levels reported to occur in Alzheimer's disease.     

Malate dehydrogenase and glucose-6-phosphate dehydrogenase, key markers for studying the genetic diversity of Actinobacillus actinomycetemcomitans

Abstract Cell-free extracts of strains belonging to the 5 serotypes of A. actinomycetemcomitans were screened for several enzymes. Enzymes representative of the pentose phosphate pathway/hexose monophosphate shunt and the TCA cycle were present. Of these glucose-6-phosphate dehydrogenase (G6PDH) and malate dehydrogenase (MDH) were the most readily detected and stable. MDH and G6PDH retained more than 50% of their activities at alkaline pHs (10–11) for up to 6 h and 3 h at 25°C, respectively, while at pH 6.5, 50% of their activities were lost within 2–3 h. The K _m for malate oxidation catalysed by MDH was 5.8×10⁻⁴ M while that for glucose-6-phosphate oxidation was 2.0×10⁻⁴ M. The pH optima for MDH and G6PDH oxidation activities were 10 and 9.5, respectively. Among the 5 designated serotypes of A. actinomycetemcomitans three groups were delineated by multilocus enzyme electrophoresis using MDH and G6PDH.     

A relationship between irradiation, carbohydrates and rooting in cuttings of Pisum sativum

Rooting ability was studied for cuttings derived from pea plants ( Pisum sativum , L. cv. Alaska) grown in controlled environment rooms. When the cuttings were rooted at 70 μmol m⁻² s⁻, ¹ (photosynthetic photon flux density) or more, a stock plant irradiance at 100 μmol m⁻² s⁻¹ decreased rooting ability in cuttings compared to 5 μmol m⁻², s⁻¹, However, cuttings rooted at 160 μmol m⁻² s⁻¹ formed more roots compared to 5 (μmol m⁻² s⁻¹. Although a high irradiance increased the number of roots formed, it could not overcome a decreased potential for root formation in stock plants grown at high irradiance. Light compensation point and dark respiration of cuttings decreased by 70% during the rooting period, and the final levels were strongly influenced by the irradiance to the cuttings. Respiratory O₂ uptake decreased in the apex and the base of the cutting from day 2 onwards, whereas a constant level was found in the leaves. Only the content of extractable fructose, glucose, sucrose and starch varied during the early part of the rooting period. We conclude that the observed changes in the cuttings are initiated by excision of the root system, and are not involved in the initiation of adventitious roots.     

Normal ranges of some blood chemistry parameters in adult farmed Atlantic salmon, Salmo salar

Blood samples from healthy adult Atlantic salmon fed an optimal diet in net sea pens were collected at intervals from October to May. Haematological determinations and biochemical serum analyses were carried out on 20 fish in each of seven samples. The ranges of haemato-logical values for sample means were: haematocrit 44–49%, haemoglobin 8.9–10.4 g 100ml⁻¹, red blood cell count 0.85–1.10 × 10¹² l⁻¹, MCV 441–553 × 10⁻¹⁵ 1, MCH 94–106 × 10⁻⁶ g, MCHC 19.4–21.7 g 100ml⁻¹ and leucocrit 0.43–0.96%. The ranges of enzyme activities in serum, for sample means, were: alkaline phosphatase 647–988Ul⁻¹, aspartate aminotrans-ferase 202–351 Ul⁻¹ and alanine aminotransferase 4–8 Ul⁻¹. The ranges of the other parameters analyzed in serum were: total protein 41.6–56.6 gl⁻¹, albumin 18.3–24.3 gl⁻¹, albumin/total protein ratio 39.3–44.0%, creatinine 26–46 μmol, triglycerides 2.53–4.98 μmol and cholesterol 9.3–12.8 μmol. These values are considered to be the normal ranges in healthy fish. Variations due to seasonal changes, and the clinical significance of the selected parameters, are discussed. Data showing the reproducibility of the biochemical analyses in serum are presented.     

THE RELEASE OF COPPER-COMPLEXING LIGANDS BY THE BROWN ALGA FUCUS VESICULOSUS (PHAEOPHYCEAE) IN RESPONSE TO INCREASING TOTAL COPPER LEVELS

The growth of Fucus vesiculosus L. germlings in chemically defined culture media containing a range of Cu concentrations (20–1000 nM) was monitored simultaneously with measurement of the Cu speciation in the media by competitive equilibrium-adsorptive cathodic stripping voltammetry. Fucus vesiculosus germlings were found to exude Cu-complexing ligands with conditional stability constants of the order of 1.6 × 10¹¹. Ligand concentrations increased with increasing total dissolved Cu concentrations (Cu_T) until a concentration of 500–800 neq Cu·L⁻¹ was reached. Concentrations of the ligand exceeded Cu_T in treatments containing 20 and 100 nM Cu, were similar to Cu_T in the 500-nM Cu treatment, but were less than Cu_T in the 1000-nM treatment. Therefore, [Cu²⁺] were calculated to be at concentrations of 10⁻¹¹− 10⁻¹⁰ M in the 20- and 100-nM treatments, 10⁻⁹ M in the 500-nM treatment, and 10⁻⁷ M in the 1000-nM treatment. Growth rates were lowest at Cu²⁺ concentration > 10⁻⁹. These results are discussed within the context of the potential roles for exuded copper-complexing ligands.