EC Treatment Research Articles

TEMPERATURE EFFECTS ON PHOTOSYNTHESIS, GROWTH RESPIRATION, AND MAINTENANCE RESPIRATION OF MARIGOLD

TEMPERATURE EFFECTS ON PHOTOSYNTHESIS, GROWTH RESPIRATION, AND MAINTENANCE RESPIRATION OF MARIGOLD

Anatomical and Eco-Physiological Changes in Leaves of Couch-Grass (Elymus repens L.), a Temperate Loess Grassland Species, after 7 Years Growth Under Elevated CO<sub>2</sub> Concentration

Leaf anatomy and eco-physiology of Elymus repens, a temperate loess grassland species, were determined after seven years of exposure to 700 μmol (CO2) mol−1 (EC). EC treatment resulted in significant reduction of stomatal density on both surfaces of couch-grass leaves. Thickness of leaves and that of the sclerenchyma tissues between the vessels and the adaxial surfaces, the area of vascular bundle, and the volumes of phloem and tracheary increased at EC while abaxial epidermis and the sclerenchyma layer between the vessel and the abaxial surface were thicker at ambient CO2 concentration (AC). Stomatal conductance and transpiration rates were lower in EC, while net CO2 assimilation rate considerably increased at EC exposure. Contents of soluble sugars and starch were higher in EC-treated couch-grass leaves than in plants grown at AC.

Light and water-use efficiencies of pine shoots exposed to elevated carbon dioxide and temperature.

An automatic gas exchange system was used to continuously measure water and carbon fluxes of attached shoots of Scots pine trees (Pinus sylvestris L.) grown in environment-controlled chambers for a 3-year period (1998-2000) and exposed to either normal ambient conditions (CON), elevated CO2 (+350 micro mol mol-1; EC), elevated temperature (+2-6 degrees C; ET) or a combination of EC and ET (ECT). EC treatment enhanced the mean daily total carbon flux per unit projected needle area (Fc.d) by 17-21 %, depending on the year. This corresponds to a 16-24 % increase in light-use efficiency (LUE) based on incident photosynthetically active radiation. The EC treatment reduced the mean daily total water flux (Fw.d) by 1-12 %, corresponding to a 13-35 % increase in water-use efficiency (WUE). The ET treatment increased Fc.d by 10-18 %, resulting in an 8-19 % increase in LUE, and Fw.d by 48-74 %, resulting in a reduction of WUE by 19-34 %. There was no interaction between CO2 and temperature elevation in connection with either carbon or water fluxes, as the carbon flux responded similarly in both ECT and EC, while the water flux in the ECT treatment was similar to that in ET. Regressions indicated that the increase in maximum LUE was greater with increasing air temperature, whereas changes in WUE were related only to high vapour pressure deficit. Furthermore, changes in LUE and WUE caused by ECT treatment displayed strong diurnal and seasonal variation.

Seasonal variation in respiration of 1-year-old shoots of scots pine exposed to elevated carbon dioxide and temperature for 4 years.

Sixteen 20-year-old Scots pine (Pinus sylvestris L.) trees growing in the field were enclosed for 4 years in environment-controlled chambers that maintained: (1) ambient conditions (CON); (2) elevated atmospheric CO2 concentration (ambient + 350 micro mol mol-1; EC); (3) elevated temperature (ambient +2-6 degrees C; ET); or (4) elevated CO2 and elevated temperature (ECT). The dark respiration rates of 1-year-old shoots, from which needles had been partly removed, were measured over the growing season in the fourth year. In all treatments, the temperature coefficient of respiration, Q10, changed with season, being smaller during the growing season than at other times. Respiration rate varied diurnally and seasonally with temperature, being highest around mid-summer and declining gradually thereafter. When measurements were made at the temperature of the chamber, respiration rates were reduced by the EC treatment relative to CON, but were increased by ET and ECT treatments. However, respiration rates at a reference temperature of 15 degrees C were reduced by ET and ECT treatments, reflecting a decreased capacity for respiration at warmer temperatures (negative acclimation). The interaction between season and treatment was not significant. Growth respiration did not differ between treatments, but maintenance respiration did, and the differences in mean daily respiration rate between the treatments were attributable to the maintenance component. We conclude that maintenance respiration should be considered when modelling respiratory responses to elevated CO2 and elevated temperature, and that increased atmospheric temperature is more important than increasing CO2 when assessing the carbon budget of pine forests under conditions of climate change.

Effects of single and repeated electroconvulsive shock on the social and agonistic behaviour of resident rats

The aim of this study was to determine whether electroconvulsive shock (ECS, an established antidepressant treatment), like acute and chronic antidepressant drug treatments, produces similar differential effects on the behavioural profile of resident rats expressed during social encounters with unfamiliar intruder conspecifics (resident-intruder paradigm). Thirty minute pretreatment with a single ECS suppressed both investigation and aggression directed at intruders concomitant with increased flight behaviour and marked sedation. Behavioural disruption subsided over the following 24 h. In contrast, resident rats subjected to bi-daily ECS treatment expressed elevated aggression at days 7 (four shocks) and 14 (eight shocks). Eight days after the last ECS treatment the behaviour of the resident rats had returned to pretreatment values. Additional studies showed that bi-daily ECS treatment nearly abolished 5-HT 2C receptor-mediated hypolocomotion induced by acute m-chlorophenylpiperazine ( mCPP, 2.5 mg/kg sc) challenge 24 h following 2 ECSs, while 4 ECSs only enhanced 5-HT 2A receptor-mediated head shakes induced by 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI, 2.0 mg/kg sc). These studies demonstrate that repeated ECS treatment increases the aggressive behaviour of resident rats which may be associated with adaptive changes in 5-HT 2C and 5-HT 2A receptor-mediated function. It remains to be seen whether adaptive changes in 5-HT 2C receptor function represent a common mechanism of clinical antidepressant efficacy.

Contrasting effects of elevated carbon dioxide concentration and temperature on Rubisco activity, chlorophyll fluorescence, needle ultrastructure and secondary metabolites in conifer seedlings.

Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings were grown for 50 days in growth chambers in an ambient or twice ambient carbon dioxide concentration ([CO2]) at a day/night temperature of 19/12 degrees C or 23/16 degrees C. Although elevated [CO2] (EC) had only slight effects on the growth parameters measured, elevated temperature (ET) increased above ground dry mass of both species. Among treatments, biomass accumulation of both species was greatest in the combined EC + ET treatment. The EC treatment induced thylakoid swelling and increased numbers of plastoglobuli observed in Scots pine needles. Although EC had little effect on Rubisco protein or N concentration of needles, ET had a large effect on N-containing compounds and enhanced N allocation from 1-year-old needles. Terpenoids were more responsive to EC and ET than total phenolics. Generally, terpene concentrations were reduced by EC and increased by ET. Increased terpenoid concentrations in response to ET might be associated with thermotolerance of photosynthesis. In Norway spruce, EC decreased total phenolic concentrations in needles, probably as a result of increased growth. We conclude that, in seedlings of these boreal species, the effects of elevated [CO2] on the studied parameters were small compared with the effects of elevated temperature.

Sensitivity of myeloid leukemia cells to calcium influx blockade: application to bone marrow purging.

The aim of this study was to assess the potential of store-operated Ca(2+) channel (SOC) antagonists as purging agents for leukemia cells. Clonogenic, limiting dilution, and nuclear condensation assays were used to evaluate SOC antagonist efficacy. SOC activity and endoplasmic reticulum Ca(2+) content were measured by flow cytometry. Murine bone marrow transplantation was used to determine purging efficacy and effects on hemopoietic reconstitution. Econazole (Ec) and ketotifen (Ke) were variably effective against human and murine leukemia cell lines after 24 hours of incubation. However, a 2-hour serum and bovine serum albumin-free treatment protocol with Ec was found to maximize differential sensitivity between leukemic cells and normal hemopoietic progenitors. Primary acute myelogenous leukemia blast cell viability was reduced 4.2 to 5.1 logs by 2-hour Ec treatment as measured by limiting dilution. An inverse relationship between endoplasmic reticulum Ca(2+) content and Ke sensitivity in leukemia and untransformed cells was observed. Nuclear condensation, an index of apoptosis, which occurred after 24-hour treatments with either Ec or Ke, was not observed after 2-hour serum- and bovine serum albumin-free Ec exposures; however, condensed nuclei were observed after an additional 10-hour incubation in growth medium without drug. Using bone marrow deliberately contaminated with 1% P815 cells, we showed that highly effective in vitro purging can be accomplished using Ec with no adverse effects on bone marrow reconstitution in mice. These studies suggest that SOC antagonists have potential as purging agents for residual leukemia cells present in bone marrow in the context of high-dose chemotherapy and autologous transplantation for leukemia.

Nitrification in a Vertisol subsoil and its relationship to the accumulation of ammonium-nitrogen at depth

Unusually high concentrations of ammonium have been observed in a Vertisol below 1 m depth in south-east Queensland. This study investigated the possibility that an absence of nitrification is allowing this ammonium to accumulate and persist over time, and examined the soil environmental characteristics that may be responsible for limiting nitrifying organisms. The possibility that anaerobiosis, soil acidity, soil salinity, low organic carbon concentrations, and/or an absence of active nitrifying microorganisms were responsible for limiting nitrification was examined in laboratory and field studies. The presence/absence of anaerobic conditions was determined qualitatively using a field test to give an indication of electron lability. In addition, an incubation study was conducted and soil environmental conditions were improved for nitrifying organisms by adjusting the pH from 4.4 to 7, adjusting the electrical conductivity from 1.6 to 0.5 dS/m, amending with a soluble carbon substrate at a rate of 500 mg/kg, and using microorganisms from the surface horizon to inoculate to the subsoil. Over a 180-day period no nitrification was detected in the control samples from the incubation study, indicating that an extremely low rate of nitrification is likely to be responsible for allowing ammonium to accumulate in this soil. Analysis of the effect of soil environmental conditions on nitrification revealed that anaerobic conditions did not exist at depth and that pH, EC, organic carbon, and inoculation treatments added in isolation had no effect on nitrification. However, when inoculum was added to the soil in combination with pH, a significant increase in nitrification was observed, and the greatest amount of nitrification was observed when inoculum, pH, and EC treatments were added in combination. It was concluded that the reason for the low rate of nitrification in this soil is primarily the absence of a significant population of active nitrifying microorganisms, which may have been unable to colonise the subsoil environment due to its acidic, and to a lesser extent, its saline environment.

Influence of the Seeds on Aroma of Muskmelon (Cucumis melo L.).

The influence of seeds on aromatic volatile compounds in muskmelon (Cucumis melo L. cv. Crest Earl's) fruit was investigated. There were little or no differences in sensory evaluations of aroma in pollinated fruits, whether the melons were treated with CPPU (PC treatment) or not (P treatment) ; but the sensory evaluation scores of pollinated fruit were significantly higher than those of parthenocarpic fruit (emasculated female flower treated with CPPU, EC treatment). In the sniffing experiments conducted by a sniff-GC, pollinated fruits were perceived as having a favorable aroma described as melon-like, fruity, sweet, milk-like, caramel-like, flower, coconut milk, milk coffee, and cake-like. Parthenocarpic fruit, however, was perceived as having offensive odors described as green, bitter, burnt, medicinal, smelly old socks, and oil-like. Therefore, it was speculated that seeds may be involved in the formation of aroma in melon fruit.

The effect of split-root salinity stress on tomato leaf expansion, fruit yield and quality

SummaryA crop-scale experiment between March and October 2000 investigated the effects of split-root salinity stress and rooting volume on the expansion of leaves, fruit yield and quality in two standard round fruited cultivars of tomato (Lycopersicon esculentumMill) Solairo and Espero, grown in rockwool. To implement the treatments, a split-root method was utilized whereby different levels of salinity (expressed as EC), adjusted by the addition of NaCl, was administered to two halves of a root system. The split-root high EC (2.8/8.0 dS m–1) treatment enhanced fruit quality by increasing the concentrations of sugar, acid, total soluble solids and reducing the incidence of visual defects such as uneven ripening and gold-spot. Split-root high EC did however reduce leaf area that corresponded with low K concentration in the leaf tissue. The split-root method utilized doubled the rooting volume compared with the standard single rockwool slab, but this extra rooting capacity had no detectable effect on leaf expansion, yield or fruit quality. Although there was little impact on yield for ten weeks after the imposition of the high EC split-root treatment, mean reductions in weekly yield occurred thereafter and were of the order of 9 and 13% for ‘Solairo’ and ‘Espero’ respectively through to the end of the experiment. The fall in yield was due, in part, to a decrease in fruit size. Whilst water uptake was reduced it was unclear how the effects on leaf growth and fruit yield were mediated in the shoot. Possible processes that coordinate responses to root-zone salinity stress are discussed. The potential use of the split-root system in commercial production is considered.

The effect of supplementation of root zone dissolved inorganic carbon on fruit yield and quality of tomatoes (cv ‘Daniella’) grown with salinity

The possibility that elevated root zone dissolved inorganic carbon (DIC) concentrations could increase yield and quality of Lycopersicon esculentum (L.) Mill. cv Daniella when combined with salinity in an agricultural production system was investigated. Root zone DIC was modified by supplying CO 2-enriched irrigation solutions (1 g l −1), NaHCO 3-enriched irrigation solutions (10 mM) or aerating the roots with ambient air or with air enriched with 5000 ppm CO 2. Plants were supplied with either low electrical conductivity ( EC=0.25 S m −1) nutrient solutions or with nutrient solutions supplemented with 55 mM NaCl to generate a high EC (0.7 S m −1). Plants were grown in plastic covered tunnel houses in two growing seasons to determine whether seasonal variations could alter the influence of root zone DIC on growth and yield. Although there were differences in vegetative and yield characteristics in the different seasons, no modification of the response to changes in root zone DIC was observed. With increased EC, growth and yield were decreased by 14 and 22%, respectively, relative to low EC treatments. High EC increased the total soluble solids (TSS) by ca. 18% and titratable acids by ca. 32% relative to low EC treatments. After storage for 2 weeks at 15°C, fruit of high EC treated plants was 12% less firm than that of low EC plants and no differences in TSS or acidity were found. At low EC, the HCO 3 − treatment decreased total yield and the yield of marketable fruit (>80 g) by ca. 22%, probably due to occlusion of drippers in this treatment. At high salinity levels, irrigation with DIC-enriched nutrient solutions had no significant effect on fruit yield or quality. Aeration of the roots with air containing 5000 ppm CO 2 increased the average marketable fruit weight by 7%, but had no significant effect on total yield or quality in comparison to controls. Aeration of the root zone with air containing 5000 ppm CO 2 also reduced the incidence of blossom-end rot by 57%. Overall, however, the influence of DIC enrichment of irrigation solutions and aeration of the root zone with air containing elevated CO 2 on fruit yield and quality is unlikely to be of commercial significance.

Analysis of the effect of EC and potential transpiration on vegetative growth of tomato

This paper analyses the response of vegetative growth of greenhouse tomato to both root-zone salinity and shoot-environment (potential transpiration), with the purpose of explaining the observed lack of effect on dry matter yield. A reference salinity (EC) of 2 dS m −1 was compared in three experiments with, respectively, 6.5, 8 and 9.5 dS m −1. Another experiment investigated specific effects of sodium chloride, by comparing two high-EC treatments (both 9 dS m −1), one with a high concentration of nutrients and one with addition of sodium chloride to a normal nutrient solution. The shoot-environment was either a “normal” climate regime or the same regime but with depressed potential transpiration, mainly by adaptation of the humidity set point. There was no detectable effect of the potential transpiration treatment, neither of the sodium chloride. Salinity effects on vegetative growth only showed up at EC exceeding 6.5 dS m −1. The most evident EC effect was a reduction of leaf expansion; individual leaf area was reduced by 8% per dS m −1 exceeding 6.5. This was partly compensated by a slight increase (2% per unit EC) in the number of leaves, which explains why cumulative plant leaf area decreased by about 7% per unit EC in excess of 6.5 dS m −1. Therefore, leaf area index (LAI) at the highest EC was reduced by some 20% compared to the LAI at an EC of 2 dS m −1. It is estimated that this would cause a reduction of less than 8% in light interception, and thus in dry matter produced. Indeed, differences observed in dry weight between the EC treatments were never significant.

Effect of temperature, pressure and alkaline treatments on meat meal quality

The recommendation of the 96/449/EC directive for processing mammalian animal waste does not ensure complete inactivation of transmissible spongiform encepalopathy (TSE) agents. The safety of the process might be ensured by adding alkaline treatments to the heating step. Evaluating the in vivo and in vitro nutritive value of meat meals produced according to 11 heat, time and pressure treatments, either with or without addition of alkali was completed. Meat meals were obtained from fresh soft bovine meat in a 20kg stirred displacement autoclave, resembling the standard equipment used in Italian rendering plants. Operating temperature and pressure were monitored continuously. Meat meals were analysed for crude protein and ash contents and pH was measured. The protein fraction was analysed for amino acids and lysinoalanine (LAL). Protein quality was evaluated in vivo with the rat-based protein efficiency ratio (PER) bioassay and in vitro by pepsin digestibility, the essential amino acids composition (DC-PER) and from both essential amino acid composition and enzyme digestibility (C-PER) of the protein. Compared to the standard procedure in use before 96/449/EC directive (MM8), implementing of the EC treatment did not reduce the nutritive value of the meat meal (MM), whereas negative effects were observed when the length of treatment was increased to 180min or when adding an alkaline step to the MM preparation. In particular, addition of alkali reduced the nutritive value of the MM as suggested by the PER bioassay, and increased the (LAL) content of the protein fraction. Data suggests that LAL content of the protein fraction could be used as an indicator of protein quality of meat meals. In vitro and in vivo results demonstrate the inadequacy of the in vitro technique (pepsin digestibility, C-PER and DC-PER) for evaluating the nutritive value of meat meals.

Short- versus Long-Term Effects of Elevated CO<sub>2</sub> on Night-Time Respiration of Needles of Scots Pine (Pinus sylvestris L.)

Dark respiration rate in the night (R D) was measured in five-year-old Scots pine (Pinus sylvestris L.) trees grown for two years under ambient (AC) and elevated (AC + 400 µmol mol−1 = EC) CO2 concentrations in open top chambers. Two needle age classes (i.e., current-year and one-year-old) were measured at AC and EC in both AC- and EC-grown pines. Additionally different chemical characteristics were determined on the needles, such as nitrogen (N), carbon (C), starch, and soluble sugar concentrations as well as specific leaf area. The direct, short-term and indirect, long-term effects of EC on R D for the two needle age classes were examined. R D was expressed on a per needle area, needle mass, N, C, and C/N bases. Direct effects were only pronounced in the AC treatment where inhibition of R D was found at EC in both current- and one-year-old needles. Indirect effects were only significant in one-year-old needles where a decrease was found in the EC grown trees as compared with AC ones when R D was expressed per unit needle mass, C, or C/N. R D per unit needle area and needle N were not sensitive to long-term EC, in any needle age class. Long-term EC treatment also influenced the response of the two needle age classes. One-year-old needles from the EC treatment had significantly lower R D than current-year needles, but no such response was observed in the AC treatment. Our experiment re-emphasised the importance of expressing R D on different bases for a correct interpretation of the responses to EC. Moreover, we showed that different needle age classes can respond differently to a CO2 enrichment.

Effects of Season, Needle Age, and Elevated Atmospheric CO<sub>2</sub> on Chlorophyll Fluorescence Parameters and Needle Nitrogen Concentration in Scots Pine (Pinus sylvestris)

Six-year-old Scots pine (Pinus sylvestris L.) seedlings were grown in open top chambers (OTCs) at ambient (AC) or elevated (ambient + 400 µmol mol-1; EC) CO2 concentration for three years (1996-1998). Chlorophyll (Chl) a fluorescence of current and one-year-old needles was measured in the field at two-weekly intervals in the period July-October 1998. In addition, Chl, carbon (C), and nitrogen (N) concentrations in both needle age classes were determined monthly during the same period. Chl fluorescence parameters were not significantly affected by EC, suggesting there was no response of the light reactions and the photochemical efficiency of photosystem 2. Chl concentrations were not significantly different but a reduced N concentration was observed in needles of EC treatment. Significant differences between needle age classes were observed for all parameters, but were most apparent under EC and toward the end of the growing season, possibly due to an acclimation process. As a result, significant interactions between CO2 treatment, needle age class, and season were found. This study emphasizes the importance of repeated measures including different leaf/needle age classes to assess the photosynthetic response of trees under EC.

Salinity and sodicity induced changes in dispersible clay and saturated hydraulic conductivity in sulfatic soils

Irrigation is becoming a more commonly used practice on glacially derived soils of the Northern Great Plains. Threshold salinity and sodicity water quality criteria for soil‐water compatibility in these sulfatic soils are not well defined. This study was conducted to relate soil salinity and sodicity to clay dispersion and saturated hydraulic conductivity (Ksat) in four representative soils. Soil salinity (EC treatment levels of 0.1 and 0.4 S m‐1) and sodicity (SAR treatment levels of 3, 9, and 15) levels were established to produce a range of conditions similar to those that might be found under irrigation. The response of each soil to changes in salinity and sodicity was unique. In general, as sodicity increased clay dispersion also increase, but the magnitude of the increase varied among the soils. In two of the soils, clay dispersion across a range of sodicity levels was lower under the 0.4 S m‐1 treatment than under the 0.1 S m‐1 treatment and in the other two soils, clay dispersion across a range of sodicity levels was similar between the two salinity treatments. Changes in Ksat were greatest in the finer textured soil (decreasing an order of magnitude across the range of sodicity levels), but was unchanged in the coarse textured soils. Results suggest that these sulfatic soils are more susceptible to sodicity induced deterioration than chloridic soils. These results and earlier field observations suggest that sustainable irrigation may be limited to sites with a water source having a SAR <5 and an EC not exceeding 0.3 S m‐1 for these sulfatic glacially derived soils.

Magnetic Stimulation of the Brain in Animal Depression Models Responsive to ECS

Studies in humans show antidepressant potential for transcranial magnetic stimulation (TMS). We therefore studied TMS in animal models of depression and compared its effects with those of ECS. ECS in rats has several robust behavioral effects, including enhancement of apomorphine-induced stereotypy, reduction of immobility time in the Porsolt swim test, and increases in seizure threshold for subsequent stimulation. Seven or 10 days of daily TMS consistently enhanced apomorphine-induced stereotypy, whereas a single session of TMS did not. Two TMS treatments markedly reduced immobility in the Porsolt swim test, as does ECS. A single TMS treatment markedly reduces the percentage of rats seizing in response to a ECS-like electrical stimulus to the brain 10 s later, as does an ECS treatment itself but not a sub-convulsive electrical stimulus to the brain. Long-term administration of ECS as well as other antidepressant treatments downregulates beta-adrenergic receptors. We found that TMS significantly reduced the density of [3H]CGP-12177 (a radioligand with beta-adrenergic affinity) binding sites in cortical (p < 0.05) but not hippocampal membranes. The role of monoamines in the mechanism of action of antidepressant treatments was investigated in numerous studies. Region-specific changes in the brain steady-state levels, and turnover rates of monoamines were detected 10 s after administration of a single repetitive TMS (rTMS) session. In the striatum and hippocampus, dopamine levels were increased by 25 +/- 1.5% and 18 +/- 0.8%, respectively, but were reduced in frontal cortex and decreased in the striatum and hippocampus in the TMS-treated rats with no change to the midbrain. TMS caused an increase in serotonin and 5-HIAA levels in the hippocampus but not in other brain regions examined in this study. The ability of TMS to induce behavioral and biochemical alterations similar to those of ECS may further support the potential role of TMS as an antidepressant treatment and bring us closer to the understanding of the mechanism of action of TMS.

COMBINED EFFECT OF CLIMATE AND CONCENTRATION OF THE NUTRIENT SOLUTION ON A GREENHOUSE TOMATO CROP. II: YIELD QUANTITY AND QUALITY

Growing systems that recirculate the nutrient solution are attractive, because they couple saving of water and fertilizers with decreased leaching. However, the longer irrigation water is collected and re-used, the higher the concentration of salts. Maintaining the EC of the nutrient solution within (conservative) boundaries requires flushing rates of 30 percent or more, in spite of the recirculating facilities. In order to determine the processes responsible for the reduction of fresh yield, that is often the consequence of growth under salinity stress, we investigated the effect on production (that is, yield quantity and quality) of a tomato crop, of high EC in combination with two water uptake rates. Associated results about leaf growth are presented in the first paper of this series. Climate in two identical glasshouses was controlled to maintain a constant ratio (65 percent) of potential evaporation, while preserving equal assimilation levels. Half of the rows in each house were given a 2 dS/m treatment in the root medium whereas the other half were given 10 dS/m. Leaf growth, canopy development and fresh and dry yield were traced during a whole spring growing season. Parameters of yield that were measured were: total fresh and marketable yield, fruit size distribution, fruit elasticity, fruit dry matter and sugar content, acidity and salinity. Fresh yield was affected by both treatments as follows: high EC significantly reduced yield, whereas the low transpiration treatment only mitigated the effect of high EC. In particular, in the high transpiration treatment marketable yield was reduced by 30 percent (due both to 25 percent smaller fruits and to 20 percent blossom-end rot, BER), whereas in the low transpiration treatment high EC reduced both size and yield by 15 percent, and incidence of BER was only 2 percent. Dry matter and sugar content were higher in the high EC treatments, so that total dry matter yield was the same everywhere, except the high EC, high transpiration treatment, where BER reduced marketable dry matter by 25 percent. Fruit elasticity (both at harvest and after one week) was not affected by any treatment, if differences in size were accounted for. It is concluded that an appropriate use of available tools for manipulating indoor climate, makes it possible to offset the effect of a high salinity of irrigation water. In particular, it is shown that a grower could accept a decrease in yield if there were a sufficient increment in quality of the product.

Does Ca2+ channel blockade modulate the antidepressant-induced changes in mechanisms of adrenergic transduction?

We investigated how the L-type calcium channel blockade (CCB) with nifedipine affects the cyclic AMP responses to noradrenaline or isoproterenol in cerebral cortical slices from rats receiving antidepressant treatments that induce (electroconvulsive shock, imipramine) or do not induce (amitriptyline) beta-downregulation. To assess the role of protein kinase C (PKC) in receptor crosstalk under CCB conditions, the cyclic AMP responses were tested also in the presence of a PKC activator, TPA. CCB alone induced no changes, but modulated the action of those antidepressants that down regulate the beta-adrenergic system. Chronic ECS and imipramine treatments were differently affected. ECS, under conditions of CCB, down regulated the response to isoproterenol in the presence of TPA, while imipramine ceased to block the TPA-potentiation of cyclic AMP responses. Thus, CCB affects the processes related to the antidepressant-induced changes on the crosstalk between alpha1- and beta-adrenergic receptors, depending on the specific properties of the antidepressant.

Photosynthetic responses to needle water potentials in Scots pine after a four-year exposure to elevated CO(2) and temperature.

Effects of needle water potential (Psi(l)) on gas exchange of Scots pine (Pinus sylvestris L.) grown for 4 years in open-top chambers with elevated temperature (ET), elevated CO(2) (EC) or a combination of elevated temperature and CO(2) (EC + ET) were examined at a high photon flux density (PPFD), saturated leaf to air water vapor pressure deficit (VPD) and optimal temperature (T). We used the Farquhar model of photosynthesis to estimate the separate effects of Psi(l) and the treatments on maximum carboxylation efficiency (V(c,max)), ribulose-1,5-bisphosphate regeneration capacity (J), rate of respiration in the light (R(d)), intercellular partial pressure of CO(2) (C(i)) and stomatal conductance (G(s)). Depression of CO(2) assimilation rate at low Psi(l) was the result of both stomatal and non-stomatal limitations on photosynthetic processes; however, stomatal limitations dominated during short-term water stress (Psi(l) < -1.2 MPa), whereas non-stomatal limitations dominated during severe water stress. Among the nonstomatal components, the decrease in J contributed more to the decline in photosynthesis than the decrease in V(c,max). Long-term elevation of CO(2) and temperature led to differences in the maximum values of the parameters, the threshold values of Psi(l) and the sensitivity of the parameters to decreasing Psi(l). The CO(2) treatment decreased the maximum values of V(c,max), J and R(d) but significantly increased the sensitivity of V(c,max), J and R(d) to decreasing Psi(l) (P < 0.05). The effects of the ET and EC + ET treatments on V(c,max), J and R(d) were opposite to the effects of the EC treatment on these parameters. The values of G(s), which were measured simultaneously with maximum net rate of assimilation (A(max)), declined in a curvilinear fashion as Psi(l) decreased. Both the EC + ET and ET treatments significantly decreased the sensitivity of G(s) to decreasing Psi(l). We conclude that, in the future, acclimation to increased atmospheric CO(2) and temperature could increase the tolerance of Scots pine to water stress.