Oxygen uptake in developing eggs and larvae of the cod, Gadus morhua L.

Unfertilised cod eggs showed a mean oxygen uptake rate at 5°C of 0.089 μl O₂, dry wt.⁻¹ h⁻¹; this gradually rose to 0.768 μl O₂ mg dry wt.⁻¹ h⁻¹ in eggs about to hatch. From hatching to complete yolk absorption larvae respired at 1.6 μl O₂, mg dry wt.⁻¹ h⁻¹. During starvation following yolk absorption, uptake fell significantly to 1.1 μl O₂, mg dry ⁻¹ h⁻¹. Much of this decrease in oxygen consumption was shown to be caused by reduction in activity. Loss of weight during the embryo and larval phases could not easily be reconciled with total oxygen consumption; it is suggested that cod embryos and larvae may not rely solely upon endogenous energy reserves during development.     

An investigation of the factors influencing mean cell volume in populations of the ciliate Colpidium campylum

Within the temperature range 10°C-20°C, temperature had no effect on the mean cell size of C. campylum. Population density also exerted no noticeable effect on mean cell volume. The quantity of energy consumed, however, had a marked effect. In experiments where less than 8000 μJ were consumed/individual/24 h, the mean cell volume decreased. Above this level of energy consumption mean cell volume maintained a constant level.
The maximum values obtained for cell sizes were 160–190 × 10³μm³ and the minimum values 40–100 × 10³μm³. A response to decreased food concentration and hence decreased energy consumption was obtained within the 24 h experimental period, indicating a rapid response to changed environment by the ciliates.     

More effective induction of spawning with long-acting GnRH agonist in the shi drum, Umbrina cirrosa L. (Sciaenidae, Teleostei), a valuable candidate for Mediterranean mariculture

Three experiments of spawning induction in shi drum, Umbrina cirrosa L., were performed in six different commercial Italian hatcheries from May to August (water temperatures: 19–29 °C; salinity: 21–37 p.p.t.). In the first experiment, 119 females (1–4.7 kg), subdivided into 29 lots, were injected with a single dose (2, 5, 8, 10, 15 and 20  μ g kg⁻¹ body weight) of short-acting gonadotropin- releasing hormone agonist (GnRHa-S), des-Gly10,[D-Ala6]-LH-RH ethylamide. In the other two experiments, 85 females (0.7–5.8 kg), subdivided into 22 and four lots, were treated with one (40 or 80  μ g kg⁻¹) or three doses (40  μ g kg⁻¹) of long-acting GnRHa (GnRHa-L), respectively. GnRHa-S stimulated spawning in 69% of the 29 treated lots; the number of eggs laid reached a maximum of 130 000 and a weighted mean of 29 200 total eggs kg⁻¹. GnRHa-L elicited a spawning response in 95% of the 22 one-dose treated lots; the number of laid eggs was higher than with GnRHa-S, reaching a maximum of 213 100 and a weighted mean of 59 400 total eggs kg⁻¹. The yield of developing embryos in 67% of the single GnRHa-L treatments was higher (sometimes up to three times) than with GnRHa-S. Triple treatments of the four lots of females with GnRHa-L always resulted in spawning responses; the best result corresponded to a number of total laid eggs of 358 900 eggs kg⁻¹ with a yield of 177 300 developing embryos.     

Effect of spice essential oils on growth and aflatoxin B1 production by Aspergillus flavus

Aflatoxin B¹ production by Aspergillus flavus was studied in yeast extract sucrose broth in the presence of cinnamon, clove, almond and cardamom oils. Growth and aflatoxin B₁ production was inhibited by 0.5 μl cinnamon oil ml^-1 medium and by 1 μl clove oil ml_-1. Almond and cardamom oils only affected growth when their concentration exceeded 1.25 μl ml^-1 medium. Aflatoxin B₁ production was stimulated by 0.75 and 1 μl almond oil ml^-1 medium or by 0.25 and 0.5 μl cardamom oil ml^-1.     

Inhibitory effects of sucrose fatty acid esters on survival of Yersinia enterocolitica on eggshell surface and use of blue lake as indicator of bacterial penetration into eggs

Aims:  To determine the effectiveness of sucrose monolaurate (SML) and sucrose monocaprate (SMC), alone and in combination with ethylenediaminetetraacetic acid (EDTA), propionic acid (PA) or citric acid (CA) in reducing mesophilic aerobic bacteria (MAB) and Yersinia enterocolitica O:9 populations on eggshells and their damage potential on the microstructure of shell cuticle.
Methods and Results:  Uninoculated eggs and eggs submerged in a solution of Y. enterocolitica were immersed in solutions of the various treatments. MAB and Y. enterocolitica counts on the surface of the eggs were carried out before and after treatment. MAB counts decreased less than 2 logs on uninoculated eggshells irrespective of treatment and reductions of 3·2 and 3·0 logs of Y. enterocolitica were obtained with 1000 μg ml⁻¹ SML plus 0·1% CA or 1000 μg ml⁻¹ SML plus 600 μg ml⁻¹ EDTA solutions, respectively. Y. enterocolitica 2/O:9 was recovered from natural microflora. Use of blue lake staining revealed minimal damage to the shells from the washing treatments.
Conclusions:  SML and SMC at 1000 μg ml⁻¹ combined with CA or EDTA could be effective in reducing Y. enterocolitica on eggshells with a minimal risk of later bacterial recontamination.
Significance and Impact of the Study:  Eggs are a recognized vehicle for transmission of Y enterocolitica although a prevalence of only 2·7% was detected in this study. Washing eggs in solutions containing SML or SMC could eliminate Y. enterocolitica contamination of egg shells.     

Potassium dependence and phytoplankton ecology: an experimental study

SUMMARY 1. Unialgal cultures of three species common in the freshwater phytoplankton were used to test limitation of specific growth rate and final yield in defined media of low K⁺ concentration (range <0.3–6 μmol L⁻¹ or mmol m⁻³).
2. Growth rate of the diatom Asterionella formosa was independent of K⁺ concentration above 0.7 μmol L⁻¹. Final yield was dependent on initial concentration when accompanied by K⁺ depletion below this concentration, but not by lesser depletion with more residual K⁺. Analyses of particulate K in the biomass indicated a mean final cell content of 2.8 μmol K 10⁻⁸ cells, approximately 1.0% of the organic dry weight.
3. Less detailed work with the diatom Diatoma elongatum showed no dependence of growth rate or final yield upon the initial K⁺ concentration in the range 0.8–3.2 μmol L⁻¹. The phytoflagellate Plagioselmis nannoplanctica suffered net mortality in the lowest concentration tested, 0.8 μmol L⁻¹.
4. Comparison with the range of K⁺ concentration in natural fresh waters, including a depletion induced by an aquatic macrophyte, suggests that K⁺ is unlikely to limit growth of phytoplankton. Nevertheless, there can be correlation of K⁺ with lake trophy.     

Effects of light and temperature on the cell size and some biochemical components in two freshwater cryptophytes

The effects of light and temperature on cell size and cellular composition (chlorophyll, protein, carbohydrate) of two freshwater cryptophytes were studied with batch cultures. Neither of the species had a constant cell size but the size varied with growth conditions. At each temperature the smallest cells were recorded at the lowest experimental photon flux density. The smallest cells of Cryptomonas 979/67 had an average volume of 232 μm³ and the largest ones 1 020 μm³. In Cryptomonas 979/62 the smallest and largest cells measured 4 306 μm³ and 12 450 μm³. Both species increased their cellular chlorophyll content when PFB dropped below 110–120 μmol m^-2 s^-1. The highest and lowest chlorophyll contents of 979/67 were 7.45 fg μm^-3 and 0.55 fg μm^-2 respectively. For 979/62 the corresponding values were 10.23 fg μm^-3 and 0.93 fg μm^-3. In both species the protein content remained stable at PFDs higher than 110–120 μmol m^-2 S^-1. The highest content of protein measured in 979/67 was 638 fg μm^-3 and the lowest 147 fg μm^-3. For 979/62 these values were 1 036 fg μm^-3 and 148 fg μm^-3 respectively. The carbohydrate results were less clear and no pattern either in response to photon flux density or temperature was obvious. The lowest and highest contents recorded for 979/67 were 62 fg μm^-3 and 409 fg μ^-3 and for 979162, 36 fg μm^-3 and 329 fg μm^-3     

Development and characterization of a lux-modified 2,4-dichlorophenol-degrading Burkholderia sp. RASC

lux -marked biosensors for assessing the toxicity and bioremediation potential of polluted environments may complement traditional chemical techniques. lux CDABE genes were introduced into the chromosome of the 2,4-dichlorophenol (2,4-DCP)-mineralizing bacterium, Burkholderia sp. RASC c2, by biparental mating using the Tn 4431 system. Experiments revealed that light output was constitutive and related to cell biomass concentration during exponential growth. The transposon insertion was stable and did not interrupt 2,4-DCP-degradative genes, and expression of lux CDABE did not constitute a metabolic burden to the cell. A bioluminescence response was detectable at sublethal 2,4-DCP concentrations: at < 10.26 μg ml⁻¹, bioluminescence was stimulated (e.g. 218% of control), but at concentrations > 60 μg ml⁻¹ it declined to < 1%. Investigating the effect of [14C]-2,4-DCP concentration on the evolution of ¹⁴CO₂ revealed that, for initial concentrations of 2.5–25 μg ml⁻¹, ≈55% of the added ¹⁴C was mineralized after 24 h compared with < 1% at 50 and 100 μg ml⁻¹. Inhibition of 2,4-DCP mineralization between 25 and 50 μg ml⁻¹ corresponded well to the EC₅₀ value (33.83 μg ml⁻¹) obtained from bioluminescence inhibition studies. lux -marked RASC c2 may therefore be used as a functionally (i.e. 2,4-DCP degrader) and environmentally relevant biosensor of toxicity and biodegradation inhibition.     

Simultaneous phototrophic and chemotrophic growth in the purple sulfur bacterium Thiocapsa roseopersicina M1

Abstract The anoxygenic phototrophic purple sulfur bacterium Thiocapsa roseopersicina was grown in illuminated continuous cultures with thiosulfate as growth limiting substrate. Aeration resulted in completely colorless cells growing chemotrophically, whereafter the conditions were changed to a 23 h oxic/1 h anoxic regime. After 11 volume changes at a dilution rate of 0.031 h⁻¹ (35% of μ_max) a time dependent equilibrium was established. During the 23 h oxic periods bacteriochlorophyll a synthesis (BChl a ) was not observed, whereas during the 1 h anoxic periods synthesis was maximal (i.e. 1.1 μg (mg protein)⁻¹ h⁻¹). As a result the BChl a concentration gradually increased from zero to an average value over 24 h of 1.9 μg (mg protein)⁻¹. Concomitantly, the protein concentration increased from 13.9 mg 1⁻¹ during continuous oxic conditions to 28.8 mg 1⁻¹. For comparison, the protein concentration during fully phototrophic growth at an identical thiosulfate concentration in the inflowing medium was 53.7 mg 1⁻¹. The specific respiration rate was 8 μmol O₂ (mg protein)⁻¹ h⁻¹ during full chemotrophic growth and gradually decreased to 3.5 μmol O₂ (mg protein)⁻¹ h⁻¹ after 11 volume changes at the regime employed. These data show that T. rosepersicina is able to simultaneously utilize light and aerobic respiration of thiosulfate as sources of energy. The ecological relevance of the data is discussed.     

Symbiotic effectiveness, rate of respiration and glutamine synthetase activity of sodium azide-resistant strains of Rhizobium leguminosarum biovar trifolii

Nitrogen fixing efficiency of sodium azide-resistant strains of Rhizobium leguminosarum bv. trifolii was studied in symbiosis with berseem clover plants in chillum jars. Rate of respiration and glutamine synthetase activity were tested in cultured cells and nodules, respectively. It was observed that shoot dry weight and percentage shoot nitrogen were maximum in plants inoculated with strains resistant to 15 μg ml⁻¹ sodium azide. Rate of respiration in cultured cells was lowest in strains resistant to 15 μg ml⁻¹ sodium azide and highest in strains resistant to 5 μg ml⁻¹ sodium azide. A negative correlation was observed between rate of respiration (in cultured cells) and shoot dry weight of host plants. Glutamine synthetase activity was maximum in nodule extracts of host plants inoculated with strains resistant to 5 and 10 μg ml⁻¹ sodium azide, whereas it was minimum for strains resistant to 15 μg ml⁻¹ sodium azide. Hence, resistance to low doses (15 μg ml⁻¹) of sodium azide, together with lower respiratory and glutamine synthetase activities, could be used as a potential method for isolating the symbiotically effective strains of Rh. leguminosarum bv. trifolii.     

Light activates H2 15O flow in rice: Detailed monitoring using a positron-emitting tracer imaging system (PETIS)

Water (H₂ ¹⁵O) translocation from the roots to the top of rice plants ( Oryza saliva L. cv. Nipponbare) was visualized over time by a positron-emitting tracer imaging system (PETIS). H₂ ¹⁵O flow was activated 8 min after plants were exposed to bright light (1 500 μmol m⁻² s⁻¹). When the light was subsequently removed, the flow gradually slowed and completely stopped after 12 min. In plants exposed to low light (500 μmol m⁻² s⁻¹), H₂ ¹⁵O flow was activated more slowly, and a higher translocation rate of H₂ ¹⁵O was observed in the same low light at the end of the next dark period. NaCl (80 m M ) and methylmercury (1 m M ) directly suppressed absorption of H₂ ¹⁵O by the roots, while methionine sulfoximine (1 m M ), abscisic acid (10 μ M ) and carbonyl cyanide m -chlorophenylhydrazone (10 m M ) were transported to the leaves and enhanced stomatal closure, reducing H₂ ¹⁵O translocation.     

Effects of feeding and induction strategy on the production of BmR1 antigen in recombinant E. coli

Aim:  To investigate the effects of feeding and induction strategies on the production of Bm R1 recombinant antigen.
Methods and Results:  Fed-batch fermentation was studied with respect to the specific growth rate and mode of induction to assess the growth potential of the bacteria in a bioreactor and to produce high yield of Bm R1 recombinant antigen. Cells were grown at a controlled specific growth rate (μ_set) during pre-induction, followed by constant feeding postinduction. The highest biomass (24·3 g l⁻¹) was obtained during fed-batch process operated at μ_set of 0·15 h⁻¹, whereby lower μ_set (0·075 h⁻¹) gave the highest protein production (9·82 mg l⁻¹). The yield of Bm R1 was increased by 1·2-fold upon induction with 1 mmol l⁻¹ IPTG (isopropyl-β- d -thiogalactoside) compared to using 5 mmol l⁻¹ and showed a further 3·5-fold increase when the culture was induced twice at the late log phase.
Conclusions:  Combination of feeding at a lower μ_set and twice induction with 1 mmol l⁻¹ IPTG yielded the best result of all variables tested, promising an improved method for Bm R1 production .
Significance and Impact of the Study:  This method can be used to increase the production scale of the Bm R1 recombinant antigen to meet the increasing demand for Brugia Rapid^™, a commercial diagnostic test for detection of brugian filariasis.     

Aerotaxis in Desulfovibrio

Aerotaxis of two sulphate-reducing bacteria, the freshwater strain Desulfovibrio desulfuricans CSN (DSM 9104) and the marine strain Desulfovibrio oxyclinae N13 (DSM 11498), was studied using capillary microslides, microscopy and oxygen microsensors. The bacteria formed ring-shaped bands in oxygen diffusion gradients surrounding O₂ bubbles, which were placed into anoxic sulphate-free cell suspensions in capillary microslides. The radial expansion of the oxic volume by diffusion was stopped by aerobic respiration. Bands were formed by cells avoiding high O₂ levels near the O₂ bubble, as well as by cells entering from the surrounding anoxic zone. At the inner edge of the bands, O₂ levels of up to 20% air saturation (50 μM O₂) were found, while the outer edge always coincided with the oxic–anoxic interface. Ring diameters and O₂ concentrations at the inner edge of the band depended on the cell density and the strain used in the suspension. Band formation did not occur in the absence of an electron donor (5 mM lactate) or when N₂ gas bubbles were used. Both strains were highly motile with velocities of ≈ 32 μm s⁻¹ during forward runs, and 7 μm s⁻¹ during backward runs respectively. Within the bands, cells moved in circles of about 20 μm diameter, while cells outside the band exhibited straighter or only slightly bent traces. It is concluded that the capacity of respiration at high rates and the positive and negative aerotactical responses of Desulfovibrio provide an efficient strategy for removing O₂ from the habitat in situations where sufficient electron donors and high cell densities are present.     

Robust experimental design for optimizing the microbial inhibitor test for penicillin detection in milk

Aims:  To use experimental design techniques and a multiple logistic regression model to optimize a microbiological inhibition test with dichotomous response for the detection of Penicillin G in milk.
Methods and Results:  A 2³ × 2² robust experimental design with two replications was used. The effects of three control factors (V: culture medium volume, S: spore concentration of Geobacillus stearothermophilus , I: indicator concentration), two noise factors (Dt: diffusion time, Ip: incubation period) and their interactions were studied. The V, S, Dt, Ip factors and V × S, V × Ip, S × Ip interactions showed significant effects.
Conclusions:  The use of 100  μ l culture medium volume, 2 × 10⁵ spores ml⁻¹, 60 min diffusion time and 3 h incubation period is recommended. In these elaboration conditions, the penicillin detection limit was of 3·9  μ g l⁻¹, similar to the maximum residue limit (MRL). Of the two noise factors studied, the incubation period can be controlled by means of the culture medium volume and spore concentration.
Significance and Impact of the Study:  We were able to optimize bioassays of dichotomous response using an experimental design and logistic regression model for the detection of residues at the level of MRL, aiding in the avoidance of health problems in the consumer.     

Endogenous cannabinoid anandamide inhibits nicotinic acetylcholine receptor function in mouse thalamic synaptosomes

The effects of the endogenous cannabinoid anandamide [arachidonylethanolamide (AEA)] on the function of nicotinic acetylcholine receptor (nAChR) were investigated using the ⁸⁶Rb⁺ efflux assay in thalamic synaptosomes. AEA reversibly inhibited ⁸⁶Rb⁺ efflux induced by 300 μM ACh with an IC₅₀ value of 0.9 ± 2 μM. Pre-treatment with the cannabinoid (CB₁) receptor antagonist SR141716A (1 μM), the CB₂ receptor antagonist SR144528 (1 μM), or pertussis toxin (0.2 mg/mL) did not alter the inhibitory effects of AEA, suggesting that known CB receptors are not involved in AEA inhibition of nAChRs. AEA inhibition of ⁸⁶Rb⁺ efflux was not reversed by increasing acetylcholine (ACh) concentrations. In radioligand binding studies, the specific binding of [³H]-nicotine was not altered in the presence of AEA, indicating that AEA inhibits the function of nAChR in a non-competitive manner. Neither the amidohydrolase inhibitor phenylmethylsulfonyl fluoride (0.2 mM) nor the cyclooxygenase inhibitor, indomethacin, (5 μM) affected AEA inhibition of nAChRs, suggesting that the effect of AEA is not mediated by its metabolic products. Importantly, the extent of AEA inhibition of ⁸⁶Rb⁺ efflux was significantly attenuated by the absence of 1% fatty acid free bovine serum albumin pre-treatment, supporting previous findings that fatty acid-like compounds modulate the activity of nAChRs. Collectively, the results indicate that AEA inhibits the function of nAChRs in thalamic synaptosomes via a CB-independent mechanism and that the background activity of these receptors is affected by fatty acids and AEA.     

Ca2+ release from intracellular stores by thapsigargin in sea urchin eggs: Relationship to larval development and relevance in egg activation

Thapsigargin (Tg), an inhibitor of microsomal Ca²⁺ ATPase, is used as a tool to study the changes in Ca²⁺ sequestration in sea urchin eggs and their relationship to embryonic development. Micromolar amounts of Tg inhibit ATP-dependent Ca²⁺ sequestration in a dose-dependent and non-reversible manner, depending on the bulk of biological material used. IC_5O values are 1 nmol/L and 1–10μmol/L, respectively, in the cortical Ca²⁺ stores (isolated cortices preparation) and in digitonin-permeabilized eggs, a preparation giving access to the deeper reticulum compartment. Micromolar Tg does not induce Ca²⁺ release from ⁴⁵Ca pre-loaded cortices but leads to a loss of 25% of the total Ca²⁺ content from the cortical area. Using microspectrofluorimetry of fura-2-loaded eggs, we found that 10 μmol/L Tg induced a moderate rise in cytosolic Ca²⁺ activity as compared with the fertilization-induced Ca²⁺ transient whether eggs were fertilized or not. Early events related to fertilization as, for example, elevation of the fertilization envelope, proton excretion and sustained increase of amino acid uptake, are triggered by 10μmol/L Tg but with a delayed onset relative to sperm-induced effects. The present findings indicate that although it triggers most fertilization-related events, Tg cannot be considered as a true mitotic agent in sea urchin eggs. When added after fertilization, Tg affects cleavage and the further embryonic development giving rise to abnormalities comparable to the animalized larvae obtained with other compounds responsible for the inhibition of reticular Ca²⁺ sequestration.     

Kinetics of photoautotrophic growth of Marchantia polymorpha cells in suspension culture

Chlorophyllous, cultured cells of Marchantia polymorpha L. (HYA-2 cell line) grow actively under photoautotrophic (lithotrophic) conditions. The maximum specific growth rate (μ_cell) was 0.64 day⁻¹ and the doubling time was 1.08 days under optimum conditions (165 μmol m⁻² s⁻¹, 1% carbon dioxide enriched atmosphere, 25^°C). The photosynthetic activity was 1.30 μmol CO₂-fixed (10⁶ cells)⁻¹ h⁻¹ [66 μmol (mg chlorophyll)⁻¹ h⁻¹] in the exponential phase. The growth course has two distinct phases, an exponential and a linear one. The exponential phase is observed as long as the population density is sufficiently low (less than 7.9 × 10⁶ cells ml⁻¹), so that practically all individual cells directly receive the full incident light. The effect of light on the specific growth rate is a linear function of photon flux density. Linear growth occurs after the population density is so high that the incident light is almost completely absorbed by the cell suspension. The growth rate is a logarithmic function of photon flux density, in contrast to the specific growth rate, and saturates at high photon flux densities. The conditions of maximum growth, however, are not wellbalanced between cell mass production and cell division. Therefore, the maximum growth does not continue for a long time.     

In vitro efficacy of nisin Z against Candida albicans adhesion and transition following contact with normal human gingival cells

Aim:  To investigate the nisin Z innocuity using normal human gingival fibroblast and epithelial cell cultures, and its synergistic effect with these gingival cells against Candida albicans adhesion and transition from blastospore to hyphal form.
Methods and Results:  Cells were cultured to 80% confluence and infected with C. albicans in the absence or presence of various concentrations of nisin Z. Our results indicate that only high concentrations of nisin Z promoted gingival cell detachment and differentiation. Determination of the LD₅₀ showed that the fibroblasts were able to tolerate up to 80  μ g ml⁻¹ for 24 h, dropping thereafter to 62  μ g ml⁻¹ after 72 h of contact, compared to 160  μ g ml⁻¹ after 24 h, and 80  μ g ml⁻¹ after 72 h recorded by the gingival epithelial cells which displayed a greater resistance to nisin Z. The use of nisin Z even at low concentration (25  μ g ml⁻¹) at appropriate concentrations with gingival cells significantly reduced C. albicans adhesion to gingival monolayer cultures and inhibited the yeast's transition.
Conclusion:  These findings show that when used at non-toxic levels for human cells, nisin Z can be effective against C. albicans adhesion and transition and may synergistically interact with gingival cells for an efficient resistance against C. albicans .
Significance and Impact of the Study:  This study suggests the potential usefulness of nisin Z as an antifungal agent, when used in an appropriate range.     

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk-sac, preflexion, flexion and post-flexion larval stages.
Oxygen uptake rates of eggs increased linearly from 0.024 μl O₂ per egg h^-1 (0·323 μl O₂ mg^-1 dry wt h^-1) by blastulae to 0·177 μlO₂ per egg h^-1 (2·516 μlO₂mg ¹dry wth^-1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%₀).
Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O₂ per larva h^-1 shortly after hatching to 18·880 μl O₂ per larva h^-1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass-specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O₂ mg ¹dry wt h^-1).
Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk-sac larvae ( Q₁₀ = 2·75) than in postflexion larvae ( Q₁₀ = 1·40).     

Irradiance levels affect growth parameters and carotenoid pigments in kale and spinach grown in a controlled environment

Carotenoids play critical roles in both light harvesting and energy dissipation for the protection of photosynthetic structures. However, limited research is available on the impact of irradiance on the production of secondary plant compounds, such as carotenoid pigments. Kale ( Brassica oleracea L.) and spinach ( Spinacia oleracea L.) are two leafy vegetables high in lutein and β-carotene carotenoids. The objectives of this study were to determine the effects of different irradiance levels on tissue biomass, elemental nutrient concentrations, and lutein β-carotene and chlorophyll (chl) pigment accumulation in the leaves of kale and spinach. 'Winterbor' kale and 'Melody' spinach were grown in nutrient solution culture in growth chambers at average irradiance levels of 125, 200, 335, 460, and 620 μmol m⁻² s⁻¹. Highest tissue lutein β-carotene and chls occurred at 335 μmol m⁻² s⁻¹ for kale, and 200 μmol m⁻² s⁻¹ for spinach. The accumulations of lutein and β-carotene were significantly different among irradiance levels for kale, but were not significantly different for spinach. However, lutein and β-carotene accumulation was significant for spinach when computed on a dry mass basis. Identifying effects of irradiance on carotenoid accumulation in kale and spinach is important information for growers producing these crops for dry capsule supplements and fresh markets.