Morphological and physiological responses of canola (Brassica napus) siliquas and seeds to UVB and CO2 under controlled environment conditions

Combined effects of UVB radiation and CO₂ concentration on plant reproductive parts have received little attention. We studied morphological and physiological responses of siliquas and seeds of canola (Brassica napus L. cv. 46A65) to UVB and CO₂ under four controlled experimental conditions: UVB radiation (4.2 kJ m⁻² d⁻¹) with ambient level of CO₂ (370 μmol mol⁻¹) (control); UVB radiation (4.2 kJ m⁻² d⁻¹) with elevated level of CO₂ (740 μmol mol⁻¹); no UVB radiation (0 kJ m⁻² d⁻¹) with ambient level of CO₂ (370 μmol mol⁻¹); and no UVB radiation (0 kJ m⁻² d⁻¹) with elevated level of CO₂ (740 μmol mol⁻¹). UVB radiation affected the outer appearance of siliquas, such as colour, as well as their anatomical structures. At both CO₂ levels, the UVB radiation of 4.2 kJ m⁻² d⁻¹ reduced the size of seeds, which had different surface patterns than those from no UVB radiation. At both CO₂ levels, 4.2 kJ m⁻² d⁻¹ of UVB decreased net CO₂ assimilation (A_N) and water use efficiency (WUE), but had no effect on transpiration (E). Elevated CO₂ increased A_N and WUE, but decreased E, under both UVB conditions. At both CO₂ levels, the UVB radiation of 4.2 kJ m⁻² d⁻¹ decreased chlorophyll fluorescence, total chlorophyll (Chl), Chl a and Chl b, but had no effect on the ratio of Chl a/b and the concentration of UV-screening pigments. Elevated CO₂ increased total Chl and the concentration of UV-screening pigments under 4.2 kJ m⁻² d⁻¹ of UVB radiation. Neither UVB nor CO₂ affected wax content of siliqua surface. Many significant relationships were found between the above-mentioned parameters. This study revealed that UVB radiation exerts an adverse effect on canola siliquas and seeds, and some of the detrimental effects of UVB on these reproductive parts can partially be mitigated by CO₂.     

Protein-based complex medium design for recombinant serine alkaline protease production

This work reports on the design of a complex medium based on simple and complex carbon sources, i.e. glucose, sucrose, molasses, and defatted-soybean, and simple and complex nitrogen sources, i.e. (NH₄)₂HPO₄, casein, and defatted-soybean, for serine alkaline protease (SAP) production by recombinant Bacillus subtilis carrying pHV1431::subC gene. SAP activity was obtained as 3050 U cm⁻³ with the initial defatted-soybean concentration C_soybean^o=20 kg m⁻³ and initial glucose concentration C_G^o=8 kg m⁻³; whereas, addition of the inorganic nitrogen source (NH₄)₂HPO₄ decreased SAP production considerably. Further increase in SAP production (3850 U cm⁻³) was obtained when sucrose was replaced with glucose at C_sucrose^o=15 kg m⁻³ and C_soybean^o=20 kg m⁻³. Nevertheless, when molasses was replaced with sucrose, the maximum activity was obtained with molasses having 10 kg m⁻³ initial sucrose concentration and C_soybean^o=15 kg m⁻³as 2130 U cm⁻³; moreover, when casein was replaced with defatted-soybean SAP production decreased considerably (ca. 250 U cm⁻³). Thereafter, the effects of inorganic ionic compounds were investigated; and except phosphate, inorganic compounds supplied from defatted-soybean were found to be sufficient for the bioprocess. The highest SAP activity was obtained as 5350 U cm⁻³ in the medium that contained (kg m⁻³): C_soybean^o=20, C_sucrose^o=15, C_Na2HPO4^o=0.021, and C_NaH2PO4^o=2.82, that was 6.5-fold higher than that of the SAP produced in the defined medium. By using the designed complex medium, oxygen transfer characteristics of the bioprocess were investigated; and, Damköhler number that is the oxygen transfer limitation increases with the cultivation time until t=14 h; and, at t>20 h both mass transfer and biochemical reaction resistances were effective. Overall oxygen transfer coefficient varied between 0.010 and 0.044 s⁻¹; volumetric oxygen uptake rate varied between 0.001 and 0.006 mol m⁻³ s⁻¹; and specific oxygen uptake rate varied between 0.0001 and 0.0022 mol kg⁻¹ DW s⁻¹ throughout the bioprocess.     

The response of an emergent sedge Bolboschoenus medianus to salinity and nutrients

The potential for nutrient load (30, 100 and 350 g N m⁻² per year) to alter plant performance under saline conditions (control, 4.5, 9 and 13 dS m⁻¹) was examined in the sedge Bolboschoenus medianus. Relative growth rates (RGR) across nutrient loadings ranged from 30.2 to 41.8 mg g⁻¹ per day in controls and were reduced to 20.9–28.5 mg g⁻¹ per day by salinities of 13 dS m⁻¹. Whilst higher nutrient loads generally increased RGR, the response was smaller at higher salinities. Responses to salinity and nutrient load were specific. Nutrient load increased the RGR via increases in the leaf area ratio (LAR). The LAR ranged from 1.9 to 2.1 m² kg⁻¹ across salinity treatments at 30 g N m⁻² per year, and increased to 2.5–2.8 m² kg⁻¹ at 350 g N m⁻² per year. Salinity reduced the RGR via a reduction in the net assimilation rate (NAR). The NAR in control plants ranged from 14.7 to 16 g m⁻² per day across nutrient loadings and decreased to 11–12 g m⁻² per day at 13 dS m⁻¹. Carbon isotope discrimination of leaves decreased by 2–3‰ in response to 13 dS m⁻¹ at the lower nutrient loadings. A prominent response of B. medianus to salinity was a change in biomass allocation from culms to tubers. In contrast, the response to nutrient load was characterised by a shift in biomass allocation from roots to leaves.     

Overexpression of serine alkaline protease encoding gene in Bacillus species: performance analyses

Bacillus species carrying subC gene encoding serine alkaline protease (SAP) enzyme were developed in order to increase the yield and selectivity in the bioprocess for SAP production. For this aim, subC gene was cloned into pHV1431 Escherichia coli–Bacillus shuttle vector, and transferred into nine host Bacillus species, i.e. B. alvei, B. amyloliquefaciens, B. badius, B. cereus, B. coagulans, B. firmus, B. licheniformis, B. sphaericus and B. subtilis. The influence of the host Bacillus species on SAP production on a defined medium with glucose was investigated in bioreactor systems. For each of the recombinant (r-) Bacillus species, effects of initial glucose concentration on cell growth and SAP production were investigated; and, physiological differences and similarities between the wild-type and r-Bacillus species are discussed. The highest biomass concentration was obtained with r-B. coagulans as 3.8 kg m⁻³ at the initial glucose concentration of C_Go=20 kg m⁻³ and the highest volumetric SAP activity was obtained with r-B. amyloliquefaciens as 1650 U cm⁻³ at C_Go=20 kg m⁻³. Overall SAP activity per amount of substrate consumed was the highest for r-B. sphaericus (137 U g⁻¹ cm⁻³) and r-B. licheniformis (130 U g⁻¹ cm⁻³). Among the r-Bacillus species the highest activity increase compared to the wild types was obtained with r-B. sphaericus while the lowest increase was obtained with r-B. amyloliquefaciens and r-B. licheniformis due to high SAP production potential of the wild-type strains. During storage of the host microorganisms, r-B. alvei and r-B. amyloliquefaciens were not able to bear the recombinant plasmid, probably, due to the restriction enzymes synthesized. Due to the highest stable volumetric activities r-B. licheniformis (950 U cm⁻³) and r-B. sphaericus (820 U cm⁻³) appear to be the favorable hosts for the production of SAP. All the r-Bacillus species excreted organic acids oxaloacetic and succinic acids, but, none excreted the amino acid valine. The variations in by-product distributions with each recombinant organism were also discussed.     

Ontogenetic photosynthetic changes, dispersal and survival of Thalassia testudinum (turtle grass) seedlings in a sub-tropical lagoon

Northward expansion of Thalassia testudinum (turtle grass) in Laguna Madre is occurring faster than can be explained by rhizome growth. We hypothesized that seedling establishment can account for the measured rates of meadow expansion and that seedling carbohydrate reserves are utilized until the plant is photosynthetically self-sufficient. To address seedling establishment, we estimated seed output, seedling dispersal and survival. Carbon dynamics were calculated from measurements of biomass allocation, non-structural carbohydrate carbon reserves and photosynthetic parameters in relation to T. testudinum seedling age. Potential seed production calculated for 1996 was consistent with field observations and was estimated at 66±14 seeds m⁻² bare area. Fruits can be positively buoyant for up to 10 days, while seeds were generally buoyant for <1 day. Water current measurements, made at about the time of seed release, indicate a positive net transport of 1.5 km d⁻¹ to the north. Seedling survival in laboratory culture after 6 months was 96% compared to 11% in the field after 1 year. The average root:rhizome+seed:leaf ratio changed from 0:11:1 for a 1 week old plant to 1:3:1 for a 15 month old plant. Seedlings used to determine whole plant photosynthesis ranged in age from about 1 week (0.25 months) to 15 months. Gross P_max increased from 80 to 220 μmol O₂ gdw sht⁻¹ h⁻¹, while whole plant respiration decreased from 170 to 60 μmol O₂ gdw sht⁻¹ h⁻¹. As the photosynthetic parameters changed, the average non-structural carbohydrate carbon (NSCC) reserves of the seeds decreased from 24 to 3.0 mg NSCC plant⁻¹. Subsequent increases in NSCC were the result of rhizome development. Daily carbon balance, assessed using H_sat periods of 8–18 h d⁻¹, predicts that T. testudinum seedlings become photosynthetically self-sufficient between 2 and 6 months. The unique characteristics of T. testudinum, including seed buoyancy, high seed production and survival rates, coupled with ontogenetic changes in carbon allocation and production imply that sexual reproduction can be important in the long distance dispersal and colonization for this species.     

Biomass seasonality of Caulerpa taxifolia in the Mediterranean Sea

The biomass of the introduced and invasive alga Caulerpa taxifolia was measured monthly over one year at four different sites along the French Mediterranean coast at depths of 5 and 20 m in a sheltered and an exposed area. At the 5 m depth, C. taxifolia mean biomass ranged from 203 to 518 g dry wt. m⁻², while at the 20 m depth, it ranged from 62 to 466 g dry wt. m⁻². The study clearly shows that a major characteristic of C. taxifolia is its perennial life cycle with relatively high biomass values throughout the year, in different biotopes. This could be a factor in the broad ecological impact of C. taxifolia.     

Growth and photosynthesis of Hydrocotyle ranunculoides L. fil. in Central Europe

Floating Pennywort (Hydrocotyle ranunculoides L. fil.) is a worldwide distributed aquatic plant. The species is native to North America and quite common also in Central and South America. In Europe, Japan and Australia it is known as an alien plant, sometimes causing serious problems for affected ecosystems and human use of water bodies. Starting from Western Europe with an eastwards directed spread, Floating Pennywort was recorded in Germany in 2004 for the first time. Since then, the species spread out and got established in western parts of Central Europe. For a definite prediction of the potential of a further spread, data about biology, in particular growth and photosynthesis are needed. Here, regeneration capacity, growth at different nutrient availabilities and photosynthesis of H. ranunculoides were investigated. In addition biomass samples were taken in the field. Results show an enormous regeneration capacity (e.g., by forming new shoots from small shoot fragments), increasing growth rates under increasing nutrient availability and a maximum increase of biomass reaching 0.132±0.008 g g⁻¹ dw d⁻¹. Dense populations of H. ranunculoides growing in ponds and oxbows were found at high nutrient content of the substrate, the biomass reaching there up to 532.4±14.2 g dw m⁻². Gas exchange analysis showed a physiological optimum of H. ranunculoides CO₂ uptake at temperatures between 25 and 35 °C and high photon flux densities (PPFD) above 800 μmol photons m⁻² s⁻¹. In comparison, native Hydrocotyle vulgaris showed an optimum of net photosynthesis at 20–30 °C and a light saturation of CO₂ gas exchange at 350 μmol photons m⁻² s⁻¹.     

Annual biomass and production of epiphytes in three monospecific seagrass communities of Thalassia hemprichii (Ehrenb.) Aschers

The biomass of epiphytes and seagrasses has been measured in relation to leaf age in three monospecific seagrass stands of Thalassia hemprichii (Ehrenb.) Aschers. in Papua New Guinea. From June 1981 through August 1982, biomass values for epiphytes at the three sites ranged from 5 to 70 g ADW m⁻² sediment surface at site 1, from 5 to 14 g ADW m⁻² at site 2, and from 3.5 to 7.0 g ADW m⁻² at the site 3. Annual mean epiphyte biomass values for the different sites were 1.3 g ADW m⁻² leaf surface at site 1, 1.7 g ADW m⁻² leaf surface at site 2, and 1.5 g ADW m⁻² leaf surface at site 3.

The annual mean standing crop of T. hemprichii leaves was highest at site 1 (103 g ADW m⁻². Values for site 2 and site 3 were 60 g ADW m⁻² and 41 g ADW m⁻², respectively.

Production of epiphytes was calculated in three different ways: firstly, by using biomass values for each specific leaf-age group, with corrections for colonization; secondly, by fitting the biomass values with a specific growth curve; and thirdly, by estimated the rate of biomass accumulation. On an area basis, production of epiphytes on leaves of T. hemprichii ranged from 0.55 to 3.97 g ADW m⁻² day⁻¹ at site 1, from 0.17 to 0.73 g ADW m⁻² day⁻¹ at site 2, and from 0.24 to 0.68 g ADW m⁻² day⁻¹ at site 3.     

Diurnal light curves and landscape-scale variation in photosynthetic characteristics of Thalassia testudinum in Florida Bay

When using pulse-amplitude modulated (PAM) fluorometry to measure landscape-scale photosynthetic characteristics, diurnal variations in fluorescence during sampling may confound the assessment of the physiological condition. In this study, two photophysiological assessment techniques: Diurnal Yield and Diurnal Rapid Light Curve (RLC) were investigated in an attempt to incorporate the temporal and spatial scales of sampling into a physiological assessment of Thalassia testudinum in Florida Bay. Photosynthesis–irradiance (P–E) curves were calculated using both methods and the ability of each to predict the relationship between relative electron transport rates and irradiance was assessed. Both methods had limitations in providing consistent estimates of photosynthetic efficiency or capacity. The Diurnal Yield method produced unrealistically high predictions of photosynthetic capacity (relative electron transport rate (rETR_max), 417–1715) and saturation irradiance (I_k, 1045–4681 μmol photons m⁻² s⁻¹). In contrast, the Diurnal RLC method generally produced predictions of rETR_max (100–200) and I_k (300–500 μmol photons m⁻² s⁻¹) which were similar to average values calculated from each day's RLCs. The Diurnal RLC method was unable to predict photosynthetic efficiency () only when ambient irradiances were continuously >I_k during the sampling period. We believe that with sampling modifications in high-light or shallow environments, such as starting sampling earlier in the morning, extending sampling later in the day, or using the average from each day's RLCs, that the Diurnal RLC method can produce representative estimates of rETR_max, , and I_k, providing a method to characterize seagrass photosynthesis at the landscape-level. The Diurnal RLC method does not negate Diurnal variation but it produces a curve that incorporates the changing ambient light environment into the assessment of seagrass physiological status.     

Growth, nodulation and nitrate reductase activity in the aquatic legume Neptunia plena (L.) benth. At different external nitrate concentrations

The effects of different external nitrate concentrations (0 (control), 1, 50, 100, 500, 1000 and 20 000 mmol m⁻³) on growth, nodulation and nitrate-reductase activity (NRA) of inoculated Neptunia plena (L.) Benth. were examined.

Plants given 500 and 1000 mmol m⁻³ nitrate had greater (P < 0.05) shoot length, leaf, stem and root dry mass, and carbon and nitrogen contents than the controls and plants given 20 000 mmol m⁻³ nitrate. Nodule number was not significantly affected by nitrate concentration up to 50 mmol m⁻³, but 100 mmol m⁻³ nitrate reduced nodulation by 68% and concentrations above 100 mmol m⁻³ completely inhibited nodule development. Plants given 100–20000 mmol m⁻³ nitrate had a greater nitrate content per g leaf, stem and root dry mass (DM) than controls. Nitrate per g root DM did not increase with external nitrate concentration above 500 mmol m⁻³, but levels in leaf and stem were greater at 20 000 mmol m⁻³ nitrate than at all other concentrations. NRA per g leaf, stem and root fresh mass (FM) was greater for plants given 500–20000 mmol m⁻³ than for controls, but there was no significant increase with nitrate concentration above 500 mmol m⁻³. Substantial proportions of total plant nitrate and NRA were found in both root and shoot over the entire range of external nitrate concentrations given.

Findings for N. plena are compared with data obtained previously for terrestrial legumes.     

The dinoflagellate Alexandrium minutum in Cape Town harbour (South Africa): Bloom characteristics, phylogenetic analysis and toxin composition

A novel bloom of Alexandrium minutum occurred in an inner basin of the Cape Town harbour from November 2003 to February 2004. Cellular concentrations reached a maximum of 1.4 × 10⁸ cells l⁻¹ during the mid-December period with corresponding chlorophyll a concentrations of 243 mg m⁻³. Primary productivity measurements conducted during the latter part of the bloom revealed a maximum assimilation number of 11.17 mg C mg Chl a⁻¹ h⁻¹ during the middle of the day. Productivity during this post-peak period was sustained largely by the reduced nitrogen species NH₄ and urea (96%) as measured using ¹⁵N tracer techniques. The large subunit ribosomal DNA sequence of A. minutum isolates from Cape Town harbour was identical to conspecifics collected in Western Europe and in Australia. The composition of tetrahydropurine neurotoxins associated with paralytic shellfish poisoning (PSP) was limited to gonyautoxins (GTX1-GTX4). This profile combined with evidence of a low toxin cell quota (1.5 fmol GTX cell⁻¹) supports a close association of this taxon with other members of the A. minutum species complex, particularly from Europe. Toxin analysis from black mussels collected during this bloom indicated that the accumulated PSP toxins originated from A. minutum and not from Alexandrium catenella as is most often the case along the South African coast.     

Effects of sulfur dioxide on the development of powdery mildew of cucumber

Environment is a major factor that does influence host parasite relationships. Air pollution caused by SO₂ may directly alter the environment around the plant and pathogen. It is hypothesised that plants may respond differently to foliar pathogens in air polluted environments. To test this hypothesis, effects of intermittent exposures of SO₂ at 143, 286 and 571 μg m⁻³ were investigated on the development of powdery mildew of cucumber (Cucumis sativa) caused by Sphaerotheca fuliginea, using pre-, post- and concomitant-inoculation exposures in closed-top chambers. Sulfur dioxide (except 143 μg m⁻³) and the fungus acting alone caused chlorosis and/or necrosis, and mildew colonies on leaves, respectively and both reduced the plant growth and yield of cucumber. Fungus colonization was relatively greater on the plants exposed to 143 μg SO₂ m⁻³, but at the higher concentrations, the colonies were greatly suppressed. Gas injury on fungus-infected plants was also less in the other treatments. Conidia of S. fuliginea collected from exposed plants varied in size. Conidial germination was considerably greater at 143 μg SO₂ m⁻³. This concentration also promoted germination of the conidia exposed on glass slides. Higher concentrations (286 and 571 μg m⁻³), however, suppressed the germination of conidia from exposed plants or exposed on glass slides. The number of fibrosin bodies declined at all the concentrations. Synergistic effects of 143 μg SO₂ m⁻³ and S. fuliginea were recorded on plant growth and yield of cucumber. Sulfur dioxide at 571 μg m⁻³ and powdery mildew infection had an antagonistic effect on plant growth.     

Annual nitrogen budget of a temperate coastal barrier salt-marsh system along a productivity gradient at low and high marsh elevation

An annual nitrogen budget was established for a temperate back barrier salt-marsh system along a productivity gradient at low and high marsh elevation. We measured plant biomass and nitrogen content in three plant compartments to deduce plant N-allocation patterns. Measurements were done along a successional sequence in a salt-marsh system. In addition, N-mineralization, wet and dry atmospheric N-deposition and sediment N-deposition were measured.

Plant-species dominance changed along the successional sequence. In early stages, Elymus farctus and Spergularia media formed a large part of total plant biomass. Festuca rubra and Puccinellia maritima were dominant at intermediate stages, whereas Elymus pycnanthus and Limonium vulgare were dominant at late stages of succession. Shoot biomass was highest in June, whereas litter biomass was highest in September and December. Root biomass formed by far the largest fraction of total plant biomass, especially at a low-marsh elevation.

Wet deposition of nitrate and ammonium was 1.7 g N m⁻² yr⁻¹, whereas throughfall deposition (dry and wet deposition) amounted to 2.1–3.6 g N m⁻² yr⁻¹, and was positively related to the height of an artificial plant canopy. Sediment organic nitrogen deposition rate was 0.3–5.4 g N m⁻² yr⁻¹, and negatively related to marsh elevation. Nitrogen mineralization rate increased from 2.5–2.8 g N m⁻² yr⁻¹ in young marshes towards 8.0–12.7 g N m⁻² yr⁻¹ at older marshes, depending on marsh elevation.

At a low-marsh elevation, plant N-availability depended equally on tidal N, atmospheric N and mineralized N, especially in young marshes, whereas the decomposition pathway became more important in older marshes. Tidal N contributed most to ecoystem N-accumulation rate at early successional stages, whereas atmospheric N was more important at later stages. Tidal influence was low at high-marsh elevation sites. Here, atmospheric deposition was the dominant exogenous nitrogen source both in young and old marshes.     

Photosynthetic response of Myriophyllum salsugineum A.E. orchard to photon irradiance, temperature and external free CO2

The photosynthetic capacity of Myriophyllum salsugineum A.E. Orchard was measured, using plants collected from Lake Wendouree, Ballarat, Victoria and grown subsequently in a glasshouse pond at Griffith, New South Wales. At pH 7.00, under conditions of constant total alkalinity of 1.0 meq dm⁻³ and saturating photon irradiance, the temperature optimum was found to be 30–35°C with rates of 140 μmol mg⁻¹ chlorophyll a h⁻¹ for oxygen production and 149 μmol mg⁻¹ chlorophyll a h⁻¹ for consumption of CO₂. These rates are generally higher than those measured by other workers for the noxious Eurasian water milfoil, Myriophyllum spicatum L., of which Myriophyllum salsugineum is a close relative. The light-compensation point and the photon irradiance required to saturate photosynthetic oxygen production were exponentially dependent on water temperature. Over the temperature range 15–35°C the light-compensation point increased from 2.4 to 16.9 μmol (PAR) m⁻² s⁻¹ for oxygen production while saturation photon irradiance increased from 41.5 to 138 μmol (PAR) m⁻² s⁻¹ for oxygen production and from 42.0 to 174 μmol (PAR) m⁻² s⁻¹ for CO₂ consumption. Respiration rates increased from 27.1 to 112.3 μmol (oxygen consumed) g⁻¹ dry weight h⁻¹ as temperature was increased from 15 to 35°C. The optimum temperature for productivity is 30°C.     

Anaerobic digestion of solid slaughterhouse waste (SHW) at laboratory scale: Influence of co-digestion with the organic fraction of municipal solid waste (OFMSW)

Mesophilic anaerobic digestion of slaughterhouse waste (SHW) and its co-digestion with the organic fraction of municipal solid waste (OFMSW) have been evaluated. These processes were carried out in a laboratory plant semi-continuously operated and two set-ups were run. The first set-up, with a hydraulic retention time (HRT) of 25 days and organic loading rate (OLR) of 1.70 kg VS m⁻³ day⁻¹ for digestion, and 3.70 kg VS m⁻³ day⁻¹ for co-digestion, was not successful. The second set-up was initiated with an HRT of 50 days and an OLR of 0.9 kg VS m⁻³ day⁻¹ for digestion and 1.85 kg VS m⁻³ day⁻¹ for co-digestion. Under these conditions, once the sludge had been acclimated to a medium with a high fat and ammonia content, it was possible to decrease the HRT while progressively increasing the OLR to the values used in the first set-up until an HRT of 25 days and OLRs of 1.70 and 3.70 kg VS m⁻³ day⁻¹, for digestion and co-digestion, respectively (the same conditions of the digesters failures previously). These digesters showed a highly stable performance, volatile fatty acids (VFAs) were not detected and long chain fatty acids (LCFAs) were undetected or only trace levels were measured in the analyzed effluent. Fat removal reached values of up to 83%. Anaerobic digestion was thus found to be a suitable technology for efficiently treating lipid and protein waste.     

Solar irradiance level alters the growth of basil (Ocimum basilicum L.) and its content of volatile oils

The experiments were commenced in March 2003 and repeated in June 2003 at Sutton Bonington Campus, the University of Nottingham, UK, to investigate the effect of irradiance on plant growth and volatile oil content and composition in plants of basil. Four levels of irradiance were provided in the glasshouse, i.e. no shade (control), 25, 50 and 75% glasshouse irradiance. It suggested that basil grows well in full sun, however it can tolerate light shade. Heavy shading (75%) to provide a light integral of 5.3 moles m⁻² d⁻¹ resulted in shorter plants, lower weight, smaller leaf area, less shoots and higher specific leaf area, and also strongly reduced the rate of photosynthesis. There was no difference in CO₂ assimilation rate between 24.9 moles m⁻² d⁻¹ light integrals (no shading) and 13.5 moles m⁻² d⁻¹ light integrals (25% shading). Shading effectively reduced leaf temperature when air temperature was less than 30 °C, but heavy shading (75%) could not reduce leaf temperature when air temperature was above 36 °C due to a limitation of free air convection. Consequently, leaf temperature increased. Heavy shading strongly reduced total volatile oil content in fresh leaves, especially in older plants (shading treatment applied at the 3 leaf-pair growth stage). There were three chemical compounds in basil leaves, namely linalool, eugenol and methyl eugenol, influenced by the shading treatments. Linalool and eugenol, which contribute to the characteristic taste of basil, were significantly increased by high daily light integrals, whereas methyleugenol was increased by lower daily light integrals. No differences in the relative content of 1,8-cineole, one of the key aromatic compounds of Ocimum species, were observed.     

Growth and biochemical characterization of microalgal biomass produced in bubble column and airlift photobioreactors: studies in fed-batch culture

Relatively large (0.19 m column diameter, 2 m tall, 0.06 m³ working volume) outdoor bubble column and airlift bioreactors (a split-cylinder and a draft-tube airlift device) were compared for monoseptic fed-batch culture of the microalga Phaeodactylum tricornutum. The three photobioreactors produced similar biomass versus time profiles and final biomass concentration (4 kg m⁻³). The maximum specific growth rate observed within a daily illuminated period in the exponential growth phase, had a value of 0.08 h⁻¹ on the third day of culture. Because of night-time losses of biomass, the specific growth rate averaged over the 4-days of exponential phase was 0.021 h⁻¹ for the three reactors.

The biomass in the vertical column reactors did not experience photoinhibition under conditions (photosynthetically active daily averaged irradiance value of 1150±52 μE m⁻² s⁻¹) that are known to cause photoinhibition in conventional thin-tube horizontal loop reactors. Because of good gas-liquid mass transfer, the dissolved oxygen concentration in the reactors at peak photosynthesis remained <120% of air saturation; thus, oxygen inhibition of photosynthesis and photo-oxidation of the biomass did not occur. Carbohydrate accumulation (up to 13% w/w) by the biomass was favored during light-limited linear growth. A declining light intensity caused a more than five-fold increase in cellular carotenoids but the chlorophylls increased only by about 2.5-fold during the course of the culture. In the stationary phase, up to 2% of the biomass was chlorophylls and carotenoids constituted up to 0.5% of the biomass dry weight.     

Antimicrobial activity of steady-state cultures of Bacillus sp. CCMI 1051 against wood contaminant fungi

The effect of changing dilution rate (D) on Bacillus sp. CCMI 1051 at dilution rates between 0.1 and 0.55 h⁻¹ in a glucose-limited medium was studied. Biomass values varied between 0.88 and 1.1 g L⁻¹ at D values of 0.15–0.35 h⁻¹. Maximal biomass productivity was found to be 0.39 g L⁻¹ h⁻¹, obtained at D = 0.35 h⁻¹ and corresponding to a 54.4% conversion of the carbon into cell mass. The highest rate of glucose consumption was 4.45 mmol g⁻¹ h⁻¹ occurring at D = 0.4 h⁻¹. The glucose concentration inside the chemostat was below the detection level starting to accumulate around 0.4 h⁻¹. Growth inhibition of fifteen strains of fungi by the broth of the steady-state cell-free supernatants was assessed. Results showed that the relative inhibition differ among the target species but was not influenced by the dilution rate changing.     

Thermal conductivity and H2O content in rabbit kidney cortex and medulla

1. 1.|H₂O content and local-tissue thermal conductivity were measured in cortex and medulla of 7 freshly-excised rabbit kidneys.

2. 2.|Tissue H₂O content and thermal conductivity k (83.4% and 0.516 W m^−t K⁻¹, respectively) in the medulla were significantly higher than those (77.7% and 0.475 W m⁻¹ K⁻¹, respectively) measured in the cortex.

3. 3.|Correlations between the measured parameters are made, and the variability of previously-reported measurements of kidney-tissue thermal conductivity is discussed.

Detrital stocks and dynamics of the seagrass Posidonia oceanica (L.) Delile in the Spanish Mediterranean

Previous studies have shown that most leaf production (>90%) of the seagrass Posidonia oceanica is shed after senescence and that a substantial percentage (up to 80%) may thereafter be exported off the seagrass meadows by waves and currents. It has also been reported that P. oceanica meadows can accumulate large stocks of belowground detritus due to slow decomposition rates. However, the generality of these results across broad spatial scales is poorly known. In this report, we examine the fate of leaf production and the magnitude and dynamics of belowground detritus in 16 P. oceanica meadows distributed along the Spanish Mediterranean. Herbivores removed a small percentage of leaf production in all the meadows (≤13%), with most leaf production (>85%) being shed after senescence. Most shed leaves (>90%) were exported off the meadows by physical agents, such as waves and currents. The amount of belowground detritus stored within 10–15 cm from the sediment surface varied from ca. 70 to 7500 g DW m⁻² among the meadows examined, and they accumulated at rates ranging from ca. 65 to 650 g DW m⁻² per year. These values are large when compared to other communities of aquatic and terrestrial macrophytes. Our results show that P. oceanica meadows in the Spanish Mediterranean support high values of secondary production in other systems by exporting large amounts of leaf detritus as well as acting as substantial carbon sinks by accumulating large reservoirs of belowground detritus. Therefore, the increasing anthropogenic threats on P. oceanica could entail an important loss of secondary production and carbon storage in Mediterranean coastal ecosystems.