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).     

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     

Continuous ethanol production by flocculating yeast in the fluidized bed bioreactor

Abstract: Continuous fermentation by a highly flocculant strain of the yeast Saccharomyces cerevisiae was carried out in a tower fluidized-bed bioreactor. The synthetic and molasses media with a total sugar concentration of 17% (w/v) were used for fermentation. Different dilution rates were tested. Stable cell densities of 50 kg m^-3(dry weight) were maintained for all dilution rates. The ethanol productivity was increasing linearly with dilution rates up to 15—20 kg m^-3 h^-1. Aeration of the culture stabilized flocculating activity and viability of yeast and also permitted long-term operation of the bioreactor.     

Drinking rate, uptake of bacteria and microalgae in turbot larvae

The drinking rate of turbot larvae increased from 14 to 120 nl larva^-1 h^-1 from day 2 to 11 after hatching, which gave a slightly increased specific drinking rate (calculated per biomass) from day 2 to 7 (0·8–1·9 nl μg carbon^-1 h^-1. The clearance rate of both algae and bacteria was 10–100 times higher than the drinking rate, which indicated that the larvae had an active uptake of both algae and bacteria. On day 2 and 4 after hatching highest clearance rate was observed for Tetraselmis sp. On day 6 about the same clearance rate was observed for bacteria, Isochrysis galbana and Tetraselmis sp. Until day 4 the turbot larvae had a higher ingestion rate of Tetraselmis sp. than of I. galbana , whereas on day 6 the rates were similar (28–41 ng carbon larvae^-1 h^-1). The assimilation efficiency was somewhat higher for I. galbana than for Tetraselmis sp., and on day 6 the assimilated algae constituted 1·5 and 0·9% of the larval biomass for I. galbana and Tetraselmis sp., respectively.     

Cloning, molecular characterization and heterologous expression of AMY1, an α-amylase gene from Cryptococcus flavus

A Cryptococcus flavus gene ( AMY1 ) encoding an extracellular α-amylase has been cloned. The nucleotide sequence of the cDNA revealed an ORF of 1896 bp encoding for a 631 amino acid polypeptide with high sequence identity with a homologous protein isolated from Cryptococcus sp. S-2. The presence of four conserved signature regions, (I) ¹⁴⁴DVVVNH¹⁴⁹, (II) ²³⁵GLRIDSLQQ²⁴³, (III) ²⁶³GEVFN²⁶⁷, (IV) ³²⁷FLENQD³³², placed the enzyme in the GH13 α-amylase family. Furthermore, sequence comparison suggests that the C. flavus α-amylase has a C-terminal starch-binding domain characteristic of the CBM20 family. AMY1 was successfully expressed in Saccharomyces cerevisiae . The time course of amylase secretion in S. cerevisiae resulted in a maximal extracellular amylolytic activity (3.93 U mL⁻¹) at 60 h of incubation. The recombinant protein had an apparent molecular mass similar to the native enzyme ( c . 67 kDa), part of which was due to N-glycosylation.     

Chlorophyll fluorescence measured using the Fraunhofer line-depth principle and relationship to photosynthetic rate in the field

Abstract. A field study was conducted to determine the relationship of solar-excited chlorophyll a fluorescence to net CO₂ assimilation rate in attached leaves. The Fraunhofer line-depth principle was used to measure fluorescence at 656.3 nm wavelength while leaves remained exposed to full sunlight and normal atmospheric pressures of CO₂ and O₂. Fluorescence induction kinetics were observed when leaves were exposed to sunlight after 10 min in darkness. Subsequently, fluorescence varied inversely with assimilation rate. In the C₄ Zea mays , fluorescence decreased from 2.5 to 0.8 mW m^-2 nm^-1 as CO₂ assimilation rate increased from 1 to 8 μmol m^-2 s^-1 (r²= 0.520). In the C₃ Liquidambar styraciflua and Pinus taeda , fluorescence decreased from 6 to 2 mW m^-2 nm^-1 as assimilation rate increased from 2 to 5 or 0 to 2 μmol m^-2 s^-1 (r²= 0.44 and 0.45. respectively). The Fraunhofer line-depth principle enables the simultaneous measurement of solar-excited fluorescence and CO₂ assimilation rate in individual leaves, but also at larger scales. Thus, it may contribute significantly to field studies of the relationship of fluorescence to photosynthesis.     

Purification of an α-L-arabinofuranosidase from carrot cell cultures and its involvement in arabinose-rich polymer degradation

Konno, H., Yamasaki, Y. and Katoh, K. 1987. Purification of an α-L-arabinofurano-sidase from carrot cell cultures and its involvement in arabinose-rich polymer degradation.
An α-L-arabinofuranosidase (α-L-arabinofuranoside arabinofuranohydrolase, EC 3.2.1.55) was isolated from a homogenate of cell suspension cultures of carrot ( Daucus carota L. cv. Kintoki). The buffer-soluble enzyme was purified to homogeneity by a procedure involving ammonium sulfate fractionation, chromatography on DEAE-Sephadex A-50, Sephadex G-150, Con A-Sepharose 4B and CM-Sephadex C-50, and preparative polyacrylamide gel electrophoresis. The size of this enzyme as determined by polyacrylamide gel electrophoresis in the presence of sodium laurylsulfate and by Sephadex G-200 gel filtration was 94 and 110 kDa, respectively. The isoelectric point was at pH 4.7. The K_m and V_max values for p-nitrophenyl α-L-arabinofuranoside were 1.33 mM and 20.2 μimol (mg protein)^-1 h^-1, respectively. The optimal activity occurred at pH 4.2 with Mcllvaine buffer. The enzyme was stimulated by Ca²⁺ and Zn²⁺, whereas it was strongly inhibited by Cu²⁺, Ag²⁺, Hg²⁺, p-chloromercuri-benzoate and L-arabono-l,4-lactone. The enzyme acted on beet arabinan in an exo-fashion. Furthermore, the enzyme was partially involved in the hydrolysis of the ara-binogalactan and pectic polymer purified from carrot cell walls.     

Role of β-amylase in starch metabolism during soybean seed development and germination

Differences in starch metabolism during seed development and germination of two soybean [ Glycine max (L.) Merrill] genotypes with normal seed β-amylase activity ['Williams' ( Sp 1^b and 'Altona' ( Sp 1^b)] and two soybean genotypes with undetectable seed β-amylase activity ['Chestnut' ( Sp 1^au) and 'Altona' ( Sp 1)] were investigated. Starch and soluble sugar profiles were essentially the same during seed development and germination. Total amylase activity of Williams and Altona ( Sp 1^b) peaked just prior to seed maturity and then dropped off slowly; whereas, the total amylase activity of Chestnut and Altona ( sp 1) was very low throughout seed development and germination. The differences in amylase activity between Altona ( Sp 1 ^b) and Altona ( sp 1) was also seen in leaves. α-Amylase activity was similar in the four genotypes when β-amylase was inhibited with Hg²⁺ but was higher in the two genotypes with normal β-amylase activity when β-amylase was inhibited with heat plus Ca²⁺. Low levels of starch phosphorylase activity were detected throughout seed development and germination, and the activity was similar in three of the genotypes and higher in Altona ( sp 1).
The protein, oil and oligosaccharide contents of mature seeds of the four genotypes were similar. Altona ( sp 1 ^b) and ( sp 1), which appear to be near isogenic lines, were not different in any morphological character or yield.
Altona ( Sp 1 ^b) showed greater hydrolysis of soybean seed starch than Altona ( sp 1), but the evidence indicates that the mutation resulting in greatly reduced or missing β-amylase activity has no effect on starch metabolism of developing and germinating soybean seeds.     

Extracellular release of photosynthetic products by freshwater phytoplankton populations, with special reference to the algal species involved

SUMMARY. Over three successive years, depth profiles of C-fixation and excretion, chlorophyll- a concentrations, phytoplankton species composition and bacterial numbers were determined in Lake Vechten, a slightly eutrophic lake in The Netherlands. Special attention was given to the method used to measure extracellular release.
Excretion of dissolved organic ¹⁴C depended largely upon the photo-synthetic activity of the phytoplankton, ranging from 0–2.5 mg m^-1 h^-1, representing a percentage extracellular release (PER) of 0–25%.
During a period in August, however, a subsurface chlorophyll- a maximum at 5–7 m depth coincided with high excretion rates of up to 10 mg Cm^-3 h^-1 (PER = 55%). Phytoplankton analysis revealed a stratification in numbers of Mallomonas caudata with a maximum at 5–7 m depth.
The results suggest that in these water layers bacterial populations grew at the expense of the dissolved organic carbon compounds excreted by Mallomonas caudata. This means that extracellular release can temporarily function as an important nutrient source for the heterotrophie community in addition to the more or less constant dissolved organic carbon pool.     

A modified drop-net method for sampling mobile epifauna on marine shallow sandy bottoms

The seasonal variations in numbers and biomass of the mobile epifauna of a shallow, sandy bay in Gullmar Fjord (Sweden) was investigated during 1976–1977 using the drop-net technique. Juvenile plaice, Pleuronectes platessa L., sand goby, Pomatoschistus minutus (Pallas), and brown shrimp Crangon crangon L. are the dominant epifaunal species. A net enclosing an area of 100 m² was used, and the organisms captured were collected with a small trawl. Three stations with a water depth≤ 1 m were regularly sampled with a total number of 73 drops. Maximum abundance was for plaice in June (6 ind m^-2), for the shrimp in July-August (61 ind m^-2), and for sand goby in September (2 ind m^-2). Standing stocks (dry wt) were 0.2, 1.5 and 0.2 g m^-2 respectively. Production estimates were based on seasonal changes in size frequency and information on specific growth rates. The production rate was for plaice (0-group) 0.3 g m^-2 yr^-1, for the shrimp 1.5, and for sand goby 0.2 g m^-2 yr^-1. Reliable estimates of the absolute abundance can be derived from the mean catch per unit area only when the efficiency of the fishing gear is known. After 6 hauls with the trawl in the drop-net enclosure more than 85% of the shrimps were caught and after the fifteenth haul less than 1% were still left. The fishing efficiency of a push-net in relation to the drop-net was for the shrimp 50%, for plaice 35% and for sand goby 17%.     

Nickel and rubidium uptake by whole oat plants in solution culture

Nickel and rubidium uptake by oat plants ( Avena sativa L. cv. Victory) were examined in relation to solution temperature, solution concentrations, metabolic inhibitors, anaerobic root conditions, transpiration and time. Over a 4-h period, uptake rates for both Ni²⁺ and Rb⁺ remained constant at 23°C. Decreasing temperatures to 2°C, 20 μ M concentrations of 2,4-dinitrophenol (DNP), or anaerobic root conditions decreased Ni²⁺ and Rb⁺ uptake rates by 97 to 86% in whole plants. Treatment of excised roots with 20 μ M DNP decreased Ni²⁺ uptake by 93%. Nickel and Rb⁺ uptake rates measured as a function of the external solution concentration followed a typical parabolic curve. K_m (0.012 m M ) and V_max [2.72 μmol (g dry weight)^-1 h^-1] values for Ni²⁺ were nearly 7 times lower than those for Rb⁺ [0.09 m M and 19.2 μmol (g dry weight)^-1 h^-1]. In all experiments, Ni²⁺ and Rb⁺ showed qualitatively similar uptake patterns, but Rb⁺ uptake was quantitatively more sensitive than Ni²⁺ to experimental manipulations.     

LIGHT-DEPENDENT GROWTH, DARK SURVIVAL, AND GLUCOSE UPTAKE BY CRYPTOPHYTES ISOLATED FROM A FRESHWATER CHEMOCLINE

Clones of Cryptomonas phaseolus Skuja , Cryptomonas rostratiformis ( Skuja ) Skuja in Huber-Pestalozi, and Cryptomonas undulata Gervais were isolated from the deep chlorophyll maximum near the oxic/anoxic boundary layer of the mesoeutrophic lake Schlachtensee, Germany. Different autecological features of these species were studied in batch culture experiments . Cryptomonas cf . ovata Ehrenberg and Chroomonas sp. that never dominated in the deep chlorophyll layer were also isolated from Schlachtensee to study their light-dependent growth in comparison to the deep-living species . Cryptomonas undulata, C. cf . ovata, and C. phaseolus had a very low light compensation point ( 5–7 μmol.m^-2.s^-1 ), whereas the growth rate of Chroomonas sp. and C. rostratiformis was positive above 16 and 24 μmol.m^-2.s^-1 . Cryptomonas phaseclus and Chroomonas sp. became photoinhibited above photon flux densities of 92 and 116 μmol.m^-2.s^-1 . Cryptomonas rostratiformis, C. cf . ovata, and C. undulata reached a maximum growth rate at a considerably higher photon flux density (198–250 μmol.m^-2.s^-1 ). Cryptomonas phaseolus grew fastest under light-limiting conditions . Chyptomonas phaseolus and C. undulata were best able to suruive prolonged periods of darkness . Cryptomonas phaseolus, C. rostratiformis, and C. undulata did not show any uptake of fluorescent latex beads. When labeled glucose was provided in naturally occurring concentrations, carbon uptake by C. phaseolus, C. rostratiformis, and C. undulata was negligibly small in comparison to cellular carbon content. I suggest that the adaptation to a low-light environment is an important preadaptation for the dominance of C. phaseolus and C. undulata near the freshwater chemocline .     

A carbon budget for nematodes, rotifers and tardigrades in a Swedish coniferous forest soil

Nematodes, rotifers and tardigrades from a Swedish pine forest soil were investigated in a monthly sampling programme lasting for one year. The monthly mean values of number, biomass and oxygen consumption were estimated. All groups fluctuated rather much over the year with a summer minimum (1.1 ˙ 10⁶ animals m^-2) and a winter maximum (6.3 ˙ 10⁶ animals m^-2) for the nematodes. The reasons for these fluctuations are discussed in relation to fluctuations of water content and temperature of the soil. On an annual basis a carbon budget was calculated which gave the following values for this fauna; consumption 4.3, production 0.6, respiration 0.9 and defecation 2.8 g carbon m^-2.     

Dose responses of tsetse flies (Glossina) to carbon dioxide, acetone and octenol in the field

ABSTRACT Studies were conducted in Zimbabwe of the catch of Glossina pallidipes Austen from an electric net plus target baited with mixtures of acetone plus carbon dioxide or 1-octen-3-ol (octenol) plus carbon dioxide. For acetone dispensed alone at 5–50, 000 mg h^-1, ten-fold increments in the dose increased the catch 1.7 times. For carbon dioxide dispensed alone, dose increments from 12 to 1201 h^-1 doubled the catch, but the catch was not further increased by dispensing carbon dioxide at 600–1200 1 h^-1. For mixtures of these two odours, ten-fold increments in the dose of carbon dioxide between 12 and 12, 0001 h^-1 increased the catch c . 2.5 times if acetone was also dispensed at >50 mg h^-1; changes in the dose of acetone between 50 and 50 000 mg h^-1 did not affect the catch. The addition of octenol (0.05 mg h^-1) to carbon dioxide (12–12001 h^-1) doubled the catch. Ten-fold increments in the dose of octenol between 0.05 and 5 mg h^-1 did not increase the catch significantly and the catch was independent of changes in the dose of carbon dioxide between 120 and 12001 h^-1. The behavioural basis of the dose-response curves was investigated using an incomplete ring of electric nets to assess the flight orientation of tsetse in different odours. Upwind flight was not elicited by acetone or octenol alone, or by carbon dioxide unless it was at very high doses, however, mixtures of carbon dioxide with acetone or octenol elicited upwind flight. It is suggested that the attractiveness of mixtures of acetone and carbon dioxide is a function of the region of overlap of these two odours at above threshold concentration. Acetone and octenol on their own appear to increase the responsiveness of flies to visual cues.     

Conversion of sucrose to starch in the developing Pennisetum typhoides grain

Developing grains of pearl millet ( Pennisetum typhoides Burm. S & H cv. PIB 155) were sampled and analyzed for starch and its free-sugar precursors. The activities of invertase, sucrose-ADP (UDP) glucosyl transferase and of α-amylase and β-amylase in relation to the rate of starch accumulation in the developing grain were assayed. By culturing detached ears, the incorporation of ¹⁴C from free sugar precursors to starch was studied. The starch content gradually increased until grain maturity. The rate of starch accumulation was maximum around 12 days after anthesis. Around this period, the activities of sucrose-ADP(UDP) glucosyl transferase and α-amylase, β-amylase were also at a peak. Invertase activity was high during the early period of grain development but gradually declined as the grains matured. In the most actively metabolising milky grains, incorporation of ¹⁴C from [¹⁴C]-sugars to starch was maximum in the mid mid-milky grains. Addition of 20 m M K⁺ to the culture solution did not affect the incorporation of ¹⁴C from supplied sucrose to the free sugar pool and to the starch of the grain, but Mg²⁺ supply at 20 m M concentration lowered ¹⁴C incorporation from exogenous sucrose to grain free sugars, although the utilization of the latter for starch synthesis was enhanced.     

Oxygen consumption of East Siberian cod: no support for the metabolic cold adaptation theory

Standard metabolic rate ( R _s) at 2°C of eight East Siberian cod Arctogadus borisovi , caught in West Greenland, body mass of 601.5 ± 147.6 g (mean ± s.D.), was 40.9 ± 5.9 mg O₂ kg^-1 h^-1 and 59.0 ± 6.6mg O₂ kg^-1 h^-1 when extrapolated to a standardized 100 g fish. R _s was compared with three other Gadidae, to test the theory of metabolic cold adaptation (MCA). There was no evidence of MCA in the family.     

Growth of thermophilic obligately autotrophic hydrogen-oxidizing bacteria on thiosulfate

Thermophilic obligately autotrophic H₂-oxidizing bacteria from Icelandic hot springs were tested for growth on thiosulfate. Ten strains were tested and all grew on thiosulfate but not on sulfite or sulfur. The product of thiosulfate oxidation was sulfate. The growth rate on thiosulfate was slower (μ=0.12 h^-1) than on H₂ (μ=0.34 h^-1). Washed cells which had been grown on thiosulfate could oxidize thiosulfate rapidly but H₂-grown cells oxidized thiosulfate much more slowly and with about a 3 h lag time. The bacteria would not grow on agar medium under H₂ but grew on agar medium containing thiosulfate.     

GROWTH OF HETEROSIGMA CARTERAE (RAPHIDOPHYCEAE) ON NITRATE AND AMMONIUM AT THREE PHOTON FLUX DENSITIES: EVIDENCE FOR N STRESS IN NITRATE-GROWING CELLS

The marine alga Heterosigma carterae Hulburt (Raphidophyta) was grown in N-limiting batch cultures using either nitrate or ammonium as the N source, at photon flux densities (PFDs) of 50, 200, and 350 μmol·m^-2·s^-1 in a 12:12 h LD cycle. Carbon content could be estimated from biovolume (μg C = 0.278 × nL; R = 0.98) but not reliably from pigment content. During exponential growth, ammonium-grown cells (in comparison with nitrate-grown cells at the same PFD) attained higher growth rates by at least 20%, contained more N, and had a lower C:N ratio, higher concentrations of intracellular free amino acids, and higher ratios of glutamine: glutamate (Gln: Glu) and asparagine: aspartate (Asn:Asp). Growth was nearly light-saturated on ammonium at 200 μmol·m^-2·s^-1 (cell-specific growth rate of 1.2 d^-1) but probably not saturated in nitrate-grown cells at 350 μmol·m^-2·s^-1. PFD did not affect Gln: Glu or Asn: Asp for a given N source. These results indicate that the nitrate-growing cells were more N-stressed than those using ammonium (which in contrast were relatively C-stressed) and that this organism would show an enhanced competitive advantage against other species when supplied with a transient supply of ammonium rather than nitrate .     

The characteristics of light in floral induction in vitro of Cichorium intybus. The possible role of phytochrome

The action of light in the initiation of floral buds in vitro has been studied using monochromatic light qualities on root explants of a long day plant, Cichorium intybus L. cv. Witloof. Red light (660 nm, 0.30 W m^-2) promotes flowering, while far-red (730 nm, 0.31 W m^-2) and irradiation with combined red + far-red (0.20 + 0.41 W m^-2) have no effect. In short day conditions floral response can be obtained in two ways: 1) by interrupting the dark period with 5 brief irradiations of red light (0.45 W m^-2, 12 min) at regular intervals, although these are counteracted by far-red irradiations of equal intensity and duration; 2) by interrupting the long night with 5 h red light applied during the second third of the night, while at the beginning or at the end it is ineffective. Red light efficiency appears to depend on the photosynthetic activity of the tissues, so that flowering increases with increasing intensity of white light and is suppressed if no white light is supplied. The reproductive development is determined by the coordination of proper irradiation conditions with sufficient sensitivity of the perceiving meristematic cells. The period of highest sensitivity to environmental light conditions in the life cycle of a Cichorium root explant occurs between the 8th and the 16th day after the start of the culture. The data strongly suggest that phytochrome is involved in flower induction of Cichorium in vitro.     

Leaf Gas Exchange Characteristics in Relation to Leaf Canopy Position of Myrica faya in its Native Environment (Tenerife, Canary Islands)

Abstract: Diurnal courses of gas exchange were measured throughout one year in fully expanded current-year leaves in the uppermost canopy (sun leaves, 18 m above ground) and in the lower canopy (shade leaves, 12 m above ground) of Myrica faya Ait., a dominant component of the Canarian laurel forest in Tenerife, Canary Islands, Spain.
M. faya showed large differences between sun and shade leaves in gas exchange characteristics (about 50 % of maximum carbon assimilation rate (A_max) reduction in shade leaves, but this reduction can be higher on specific days) that were modulated by strong light attenuation and high leaf area index (LAI) of the stand. This species presented low A_max, about 10 μmol m^-2 s^-1, high maximum transpiration (E, 8 mmol m^-2 s^-1) and stomatal conductance (g_s, 750 mmol m^-2 s^-1) and very low instantaneous water use efficiency (WUE, mean maximum 1.1 mmol mol^-1) and A/g_s (mean maximum 23.5 μmol mol^-1). M. faya responded to high air vapour pressure deficit (VPD), decreasing its g_s but maintaining relatively high values of A and E during the studied period. Stomatal response to VPD showed a higher sensitivity than its congeners, M. cerifera, and Laurus azorica, tree species co-occurring in the Canarian laurel forest. In general, all these gas exchange characteristics lead us to consider this species more similar to subtropical plants of humid regions than to species of the Mediterranean region.