Expression,subcellular localization,and <Emphasis Type="Italic">cis</Emphasis>-regulatory structure of duplicated phytoene synthase genes in melon (<Emphasis Type="Italic">Cucumis melo</Emphasis> L.)

The emission of molecular iodine (I₂) from the stipe, the meristematic area and the distal blade of the brown macroalga Laminaria digitata (Hudson) Lamouroux (Phaeophyceae) was monitored under low light and dark conditions. Photosynthetic parameters were determined to investigate both the extent of stress experienced by different thallus parts and the effects of emersion on photosynthesis. Immediately after air exposure, intense I₂ emission was detectable from all thallus parts. I₂ emission declined continuously over a period of 180 min following the initial burst, but was not affected by the light regime. The total number of mole of I₂ emitted by stipes was approximately 10 times higher than those emitted from other thallus parts. Initial I₂ emission rates (measured within 30 min of exposure to air) were highest for stipes (median values: 2,999 and 5,222 pmol g⁻¹ dw min⁻¹ in low light and dark, respectively) and lower, by one order of magnitude, for meristematic regions and distal blades. After exposure to air for between 60 and 180 min, I₂ emission rates of all thallus parts were reduced by 70–80%. Air exposure resulted in a decrease of the maximum photosystem II (PSII) efficiency (F _v/F _m) by 3%, and in a 25–55% increase of the effective PSII quantum efficiency ( \Updelta F/F^￠_\textm \Updelta F/F^{\prime}_{\text{m}} ); this was caused by a higher fraction of open reaction centres (q_P), whereas the efficiency of the latter in capturing energy ( F^￠_\textv /F^￠_\textm F^{\prime}_{\text{v}} /F^{\prime}_{\text{m}} ) remained constant. The results indicate the presence of an iodine pool which is easily volatilised and depleted due to air exposure, even under apparently low stress conditions.     

Physiological characterization of ‘stay green’ wheat cultivars during the grain filling stage under field growing conditions

Rye (Secale cereale L.) chromosome arm 1RS could delay leaf senescence, and change in H₂O₂ content is a useful index for weighing the ability to delay the senescence. Two wheat cultivars, Chuannong12 (CN12) and Chuannong 18 (CN18), harboring the wheat–rye 1BL/1RS translocated chromosome were investigated for H₂O₂ change and physiological index after flowering under field conditions, and MY11, the agronomical parent of both CN12 and CN18, was used as the control. A combined change in the peak value of CdSe/ZnS quantum dot (QD) fluorescence and morphological observation indicated that the H₂O₂ contents in CN12 and CN18 were generally lower than that in MY11. They both had higher values for net photosynthetic rate (P _n), stomatal conductance (G _s), F_\textv /F_\textm^￠ F_{\text{v}} /F_{\text{m}}^{\prime } F_\textv^￠ /F_\textm^￠ F_{\text{v}}^{\prime } /F_{\text{m}}^{\prime } , and photochemical quenching of PSII (qP) than MY11 only in the late measurement stage. Some small differences were also observed, such as CN12 and CN18 wheat cultivars having higher and longer photosynthetic competence than MY11 during the grain filling stage, which perhaps resulted from a mechanism for removing oxidative species, especially H₂O₂.     

Genetic effects of forest fragmentation in high-density Araucaria angustifolia populations in Southern Brazil

Araucaria angustifolia is an endangered tropical/subtropical coniferous of great interest for conservation due its economical, ecological, and social value. Only 3% of original Araucaria forests remain, which are generally confined to small forest fragments. Forest fragmentation can have serious consequences on genetic process in tree population, affecting long-term fitness and adaptability. To investigate the effects of forest fragmentation on genetic diversity and the structure of A. angustifolia populations, the genetic diversity of eight microsatellite loci was compared in four small fragmented populations (<22 ha), four tree groups (five to 11 trees) occurring in pastures and in three plots in a large continuous population. The clearest effect of fragmentation was the loss of rare alleles (p ≤ 0.05) in fragmented populations (19.4% to 47.2%) and intermediate frequency (0.05 < p ≤ 0.25) and rare alleles (p ≤ 0.05) in tree groups (19% to 86.1%) in comparison to continuous populations. Fragmented populations have significant higher fixation index ( [^(F)]_\textIS = 0.121 \widehat{F}_{\text{IS}} = 0.121 , P < 0.05) than continuous populations ( [^(F)]_\textIS = 0.083 \widehat{F}_{\text{IS}} = 0.083 , P < 0.05). High genetic differentiation was detected among tree groups ( [^(G)]_\textST^￠ = 0.258 \widehat{G}_{{{\text{ST}}}}^{\prime } = 0.258 , P < 0.01) and low among fragments ( [^(G)]_\textST^￠ = 0.031 \widehat{G}_{{{\text{ST}}}}^{\prime } = 0.031 , P < 0.05) and continuous populations ( [^(G)]_\textST^￠ = 0.026 \widehat{G}_{{{\text{ST}}}}^{\prime } = 0.026 , P < 0.05), showing a significant bottleneck effect in tree groups. Evidence that forest fragments have experienced a recent bottleneck was confirmed in at least two studied fragments. The implications of the results for conservation of the fragmented A. angustifolia populations are discussed.     

New potent biphalin analogues containing p-fluoro-L-phenylalanine at the 4,4' positions and non-hydrazine linkers

We report the synthesis and the biological evaluation of two new analogues of the potent dimeric opioid peptide biphalin. The performed modification is based on the replacement of two key structural elements of the native biphalin, namely: the hydrazine bridge which joins the two palindromic moieties and the phenylalanine residues at the 4,4′ positions of the backbone. The new analogues 9 and 10 contain 1,2-phenylenediamine and piperazine, respectively, in place of the hydrazidic linker and p-fluoro-l-phenylalanine residues at 4 and 4′ positions. Binding values are: K_\texti^m = 0.51 \textnM K_{\text{i}}^{\mu } = 0.51\,{\text{nM}} and K_\texti^d = 12.8 \textnM K_{\text{i}}^{\delta } = 12.8\,{\text{nM}} for compound 9, K_\texti^m = 0.09 \textnM K_{\text{i}}^{\mu } = 0.09\,{\text{nM}} and K_\texti^d = 0.11 \textnM K_{\text{i}}^{\delta } = 0.11\,{\text{nM}} for analogue 10.     

Fluoride inhibition of photosystem II and the effect of removal of the PsbQ subunit

Photosystem II (PSII), the light-absorbing complex of photosynthesis that evolves oxygen, requires chloride for activation of the oxygen evolving complex (OEC). In this study, fluoride was characterized as an inhibitor of Cl⁻-activated oxygen evolution in higher plant PSII. It was confirmed to be primarily a competitive inhibitor in intact PSII, with Cl⁻-competitive inhibition constant K_i = 2 mM and uncompetitive inhibition constant \textK_\texti^￠ {\text{K}}_{\text{i}}^{\prime }  = 79 mM. A pH dependence study showed that fluoride inhibition was more pronounced at lower pH values. In order to determine the location of the fluoride effect, PSII preparations lacking various amounts of the PsbQ subunit were prepared. The competitive F⁻ inhibition constant and the Michaelis constant for Cl⁻ activation increased with loss of the PsbQ subunit, while the uncompetitive F⁻ inhibition constant was relatively insensitive to loss of PsbQ. The S₂ state EPR signals from PSII lacking PsbQ responded to Ca²⁺ and Cl⁻ removal and to F⁻ treatment similar to intact PSII, with enhancement of the g = 4.1 signal and suppression of the multiline signal, but the effects were more pronounced in PSII lacking PsbQ. Together, these results support the interpretation that the PsbQ subunit has a role in retaining anions within the OEC.     

Influence of {\text{NH - }}{{\text{S}}^\gamma } bonding interactions on the structure and dynamics of metallothioneins

Mammalian metallothioneins ( \textM₇^\textIIMTs {\text{M}}_7^{\text{IIMTs}} ) show a clustered arrangement of the metal ions and a nonregular protein structure. The solution structures of Cd₃-thiolate cluster containing β-domain of mouse β-MT-1 and rat β-MT-2 show high structural similarities, but widely differing structure dynamics. Molecular dynamics simulations revealed a substantially increased number of \textNH - \textS^g {\text{NH - }}{{\text{S}}^\gamma } hydrogen bonds in β-MT-2, features likely responsible for the increased stability of the Cd₃-thiolate cluster and the enfolding protein domain. Alterations in the \textNH - \textS^g {\text{NH - }}{{\text{S}}^\gamma } hydrogen-bonding network may provide a rationale for the differences in dynamic properties encountered in the β-domains of MT-1, -2, and -3 isoforms, believed to be essential for their different biological function.     

HNCA-TOCSY-CANH experiments with alternate <Superscript>13</Superscript>C-<Superscript>12</Superscript>C labeling: a set of 3D experiment with unique supra-sequential information for mainchain resonance assignment

Described here is a set of three-dimensional (3D) NMR experiments that rely on CACA-TOCSY magnetization transfer via the weak ³ \textJ_{\textCa\textCa} ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} coupling. These pulse sequences, which resemble recently described ¹³C detected CACA-TOCSY (Takeuchi et al. 2010) experiments, are recorded in ¹H₂O, and use ¹H excitation and detection. These experiments require alternate ¹³C-¹²C labeling together with perdeuteration, which allows utilizing the small ³ \textJ_{\textCa\textCa} ^{ 3} {\text{J}}_{{{\text{C}}\alpha {\text{C}}\alpha }} scalar coupling that is otherwise masked by the stronger ¹J_CC couplings in uniformly ¹³C labeled samples. These new experiments provide a unique assignment ladder-mark that yields bidirectional supra-sequential information and can readily straddle proline residues. Unlike the conventional HNCA experiment, which contains only sequential information to the ^{1 3} \textC^a ^{ 1 3} {\text{C}}^{\alpha } of the preceding residue, the 3D hnCA-TOCSY-caNH experiment can yield sequential correlations to alpha carbons in positions i−1, i + 1 and i−2. Furthermore, the 3D hNca-TOCSY-caNH and Hnca-TOCSY-caNH experiments, which share the same magnetization pathway but use a different chemical shift encoding, directly couple the ¹⁵N-¹H spin pair of residue i to adjacent amide protons and nitrogens at positions i−2, i−1, i + 1 and i + 2, respectively. These new experimental features make protein backbone assignments more robust by reducing the degeneracy problem associated with the conventional 3D NMR experiments.     

Deriving fluorometer-specific values of relative PSI fluorescence intensity from quenching of F 0 fluorescence in leaves of Arabidopsis thaliana and Zea mays

The effect of stepwise increments of red light intensities on pulse-amplitude modulated (PAM) chlorophyll (Chl) fluorescence from leaves of A. thaliana and Z. mays was investigated. Minimum and maximum fluorescence were measured before illumination (F ₀ and F _M, respectively) and at the end of each light step ( $ F^{\prime}_{0} $ and $ F^{\prime}_{\text{M}} $ , respectively). Calculated $ F^{\prime}_{0} $ values derived from F ₀, F _M and $ F^{\prime}_{\text{M}} $ fluorescence according to Oxborough and Baker (1997) were lower than the corresponding measured $ F^{\prime}_{0} $ values. Based on the concept that calculated $ F^{\prime}_{0} $ values are under-estimated because the underlying theory ignores PSI fluorescence, a method was devised to gain relative PSI fluorescence intensities from differences between calculated and measured $ F^{\prime}_{0} $ . This method yields fluorometer-specific PSI data as its input data (F ₀, F _M, $ F^{\prime}_{0} $ and $ F^{\prime}_{\text{M}} $ ) depend solely on the spectral properties of the fluorometer used. Under the present conditions, the PSI contribution to F ₀ fluorescence was 0.24 in A. thaliana and it was independent on the light acclimation status; the corresponding value was 0.50 in Z. mays. Correction for PSI fluorescence affected Z. mays most: the linear relationship between PSI and PSII photochemical yields was clearly shifted toward the one-to-one proportionality line and maximum electron transport was increased by 50 %. Further, correction for PSI fluorescence increased the PSII reaction center-specific parameter, 1/F ₀ ? 1/F _M, up to 50 % in A. thaliana and up to 400 % in Z. mays.     

Oxygen-dependence of metabolic rate in the muscles of craniates

We present evidence that oxygen consumption (V_\textO2 ) (V_{{{\text{O}}_{2} }} ) is oxygen partial pressure (P_\textO2 ) (P_{{{\text{O}}_{2} }} ) dependent in striated muscles and P_\textO2 P_{{{\text{O}}_{2} }} -independent in the vasculature in representatives of three craniate taxa: two teleost fish, a hagfish and a rat. Blood vessel V_\textO2 V_{{{\text{O}}_{2} }} displayed varying degrees of independence in a P_\textO2 P_{{{\text{O}}_{2} }} range of 15–95 mmHg, while V_\textO2 V_{{{\text{O}}_{2} }} by striated muscle tissue slices from all species related linearly to P_\textO2 P_{{{\text{O}}_{2} }} between 0 and 125 mmHg, despite V_\textO2 V_{{{\text{O}}_{2} }} rates varying greatly between species and muscle type. In salmon red muscle, lactate concentrations fell in slices incubated at a P_\textO2 P_{{{\text{O}}_{2} }} of either 30 or 100 mmHg, suggesting aerobic rather than anaerobic metabolism. Consistent with this finding, potential energy, a proxy of ATP turnover, was P_\textO2 P_{{{\text{O}}_{2} }} -dependent. Our data suggest that the reduction in V_\textO2 V_{{{\text{O}}_{2} }} with falling P_\textO2 P_{{{\text{O}}_{2} }} results in a decrease in ATP demand, suggesting that the hypoxic signal is sensed and cellular changes effected. Viability and diffusion limitation of the preparations were investigated using salmon cardiac and skeletal muscles. Following the initial P_\textO2 P_{{{\text{O}}_{2} }} depletion, reoxygenation of the Ringer bathing salmon cardiac muscle resulted in V_\textO2 \texts V_{{{\text{O}}_{2} }} {\text{s}} that was unchanged from the first run. V_\textO2 V_{{{\text{O}}_{2} }} increased in all muscles uncoupled with p-trifluoromethoxylphenyl-hydrazone (FCCP) and 2,4-dinitrophenol (DNP). Mitochondrial succinate dehydrogenase activity, quantified by reduction of 3-(4,5-dimethylthiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan, was constant over the course of the experiment. These three findings indicate that the tissues remained viable over time and ruled out diffusion-limitation as a constraint on V_\textO2 V_{{{\text{O}}_{2} }} .     

Parameterization of chlorophyll a-specific absorption coefficients and effects of their variations in a highly eutrophic lake: a case study at Lake Kasumigaura, Japan

The chlorophyll a-specific absorption coefficient ( a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) ) in a highly eutrophic lake can show characteristics distinct from that in the ocean due to the differences in the structure and composition of phytoplankton. In this study, investigated the variation of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in Lake Kasumigaura, a highly eutrophic lake in Japan, in association with the package effect and the effect of accessory pigments, and carried out the parameterization of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) . Although a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) did not vary spatially, it did show significant temporal variation, with a particularly high value after spring-bloom. This high a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in spring was attributed to a lower package effect and a higher proportion of carotenoid than the other samples. Although the value of a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) was correlated with the concentration of chlorophyll-a (Chl-a), the correlation coefficient was lower than those reported in the ocean. Some lake-water samples showed variations of the package effect and the effect of accessory pigments that were independent of the concentration of Chl-a, and these independent variations resulted in the weak correlation between a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) and the concentration of Chl-a. Together, these results suggest that the factors controlling a_\textph^* ( l) a_{\text{ph}}^{*} \left( \lambda \right) in highly eutrophic lakes are distinct from that in ocean samples.     

Analysis of the activation mechanism of <Emphasis Type="Italic">Pseudomonas stutzeri</Emphasis> cytochrome <Emphasis Type="Italic">c</Emphasis> peroxidase through an electron transfer chain

The activation mechanism of Pseudomonas stutzeri cytochrome c peroxidase (CCP) was probed through the mediated electrochemical catalysis by its physiological electron donor, P. stutzeri cytochrome c-551. A comparative study was carried out, by performing assays with the enzyme in the resting oxidized state as well as in the mixed-valence activated form, using cyclic voltammetry and a pyrolytic graphite membrane electrode. In the presence of both the enzyme and hydrogen peroxide, the peak-like signal of cytochrome c-551 is converted into a sigmoidal wave form characteristic of an \textE_\textr \textC_\texti^￠ {\text{E}}_{\text{r}} {\text{C}}_{\text{i}}^{\prime } catalytic mechanism. An intermolecular electron transfer rate constant of (4 ± 1) × 10⁵ M⁻¹ s⁻¹ was estimated for both forms of the enzyme, as well as a similar Michaelis–Menten constant. These results show that neither the intermolecular electron transfer nor the catalytic activity is kinetically controlled by the activation mechanism of CCP in the case of the P. stutzeri enzyme. Direct enzyme catalysis using protein film voltammetry was unsuccessful for the analysis of the activation mechanism, since P. stutzeri CCP undergoes an undesirable interaction with the pyrolytic graphite surface. This interaction, previously reported for the Paracoccus pantotrophus CCP, induces the formation of a non-native conformation state of the electron-transferring haem, which has a redox potential 200 mV lower than that of the native state and maintains peroxidatic activity.     

Injured and uninjured leaf photosynthetic responses after mechanical injury on <Emphasis Type="Italic">Nerium oleander</Emphasis> leaves,and <Emphasis Type="Italic">Danaus plexippus</Emphasis> herbivory on <Emphasis Type="Italic">Asclepias curassavica</Emphasis> leaves

Insect herbivory has variable effects on plant physiology; so greater understanding is needed about how injury alters photosynthesis on individual injured and uninjured leaves. Gas exchange and light-adapted leaf chlorophyll fluorescence measurements were collected from uninjured and mechanical partial leaf defoliation in two experiments with Nerium oleander (Apocynaceae) leaves, and one experiment with Danaus plexippus herbivory on Asclepias curassavica (Asclepiadaceae) leaves. Gas exchange impairment (lower photosynthetic rate (P _n ), stomatal conductance (g _s)) indicates water stress in a leaf, suggests stomatal limitations causing injury P _n impairment. The same pattern of gas exchange impairment also occurred on uninjured leaves opposite from injured leaves in both N. oleander experiments. This is an interesting result because photosynthetic impairment is rarely reported on injured leaves near injured leaves. No photosynthetic changes occurred in uninjured A. curassavica leaves opposite from D. plexippus-fed leaves. Partially defoliated leaves that had P _n and g _s reductions lacked any significant changes in intercellular leaf [CO₂], C _i. These results neither support, nor are sufficient to reject, stomatal limitations to photosynthesis. Manually imposed midrib vein severance in N. oleander experiment #1 significantly increased leaf C _i, indicating mesophyll limitations to photosynthesis. Maximal light-adapted leaf photochemical efficiency () and also non-photochemical quenching (q _N) were reduced by mechanical or insect herbivory to both study species, suggesting leaf trouble handling excess light energy not used for photochemistry. Midrib injury on N. oleander leaves and D. plexippus herbivory on A. curassavica leaves also reduced effective quantum yield (ΦPSII) and photochemical quenching (q _P); so reduced plastoquinone pools could lead to additional PSII reaction center closure.     

Genetic parameters and predicted selection responses for timber production traits in a Castanea sativa progeny trial: developing a breeding program

Total height, diameter, index volume, stem straightness, apical dominance, and survival were assessed at 8 years from seed in an open-pollinated progeny test of 36 families of European chestnut (Castanea sativa Miller) established at two sites in the Atlantic area of Galicia, Spain. Iterative spatial analysis was applied to eliminate the effect of the spatial dependence in the original data and to estimate accurately genetic parameters for evaluating the potential for selection of the measured trees. Spatial analysis was very beneficial for growth traits and survival, but less so if at all for form traits. Estimated individual heritabilities ranged from moderate to high for growth traits ([^(h)]_i² = 0.29 - 0.42 \widehat{h}_i^2 = 0.29 - 0.42 ) and stem straightness ([^(h)]_i² = 0.24 - 0.42 \widehat{h}_i^2 = 0.{24} - 0.{42} ). High coefficients of additive genetic variance were obtained for volume ( [^(\textC)]\textV_\textA = 36.5 - 41.5% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {36}.{5} - {41}.{5}\% ) and straightness ( [^(\textC)]\textV_\textA = 44.26 - 53.84% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {44}.{26} - {53}.{84}\% ). Phenotypic and estimated genetic correlations between growth traits were very high, and correlations between sites indicated that there was no important family × site interaction. No adverse correlations between traits were evident. The results indicate the ample potential for selection in the current progeny trial, where responses to within-family and combined selection for growth traits may be high. Accordingly, three selection scenarios were addressed with the aim to initiate the selection of individuals for implementing the Forest Breeding Plan of Galicia for European chestnut.     

Toxicity assessment of common organic solvents using a biosensor based on algal photosynthetic activity measurement

The acute toxicities of common organic solvents (e.g., methanol, ethanol, isopropanol, acetone, acetonitrile, and dimethylformamide) were evaluated using a biosensor based on microalgal photosynthesis measurement. The biosensor was air-tight, with no headspace, preventing volatile organic toxicants from escaping into the environment as well as partitioning from the aqueous phase into the headspace until equilibrium was reached. Both the incubating and exposure times were set at 10 min. It was observed that only 2 h was needed to obtain complete dose-related inhibition of photosynthetic activity. The results showed that all the tested organic solvents inhibited algal photosynthesis with EC₅₀ ranging between 589 and 2,570 mM. The inhibition of these solvents was in the order: isopropanol > acetone > acetonitrile > ethanol > dimethylformamide > methanol. The quantitative structure-activity relationship (QSAR) between toxicity data and partition coefficient of the examined compounds could be modeled as follows: ${\text{log}}_{{10}} {\text{EC}}_{{50}} \;{\left( {\mu {\text{M}}} \right)} = - 0.6428\;{\text{log}}\;P + 5.76\;{\left( {{\text{R}}^{2} \approx 0.88} \right)}The acute toxicities of common organic solvents (e.g., methanol, ethanol, isopropanol, acetone, acetonitrile, and dimethylformamide) were evaluated using a biosensor based on microalgal photosynthesis measurement. The biosensor was air-tight, with no headspace, preventing volatile organic toxicants from escaping into the environment as well as partitioning from the aqueous phase into the headspace until equilibrium was reached. Both the incubating and exposure times were set at 10 min. It was observed that only 2 h was needed to obtain complete dose-related inhibition of photosynthetic activity. The results showed that all the tested organic solvents inhibited algal photosynthesis with EC₅₀ ranging between 589 and 2,570 mM. The inhibition of these solvents was in the order: isopropanol > acetone > acetonitrile > ethanol > dimethylformamide > methanol. The quantitative structure-activity relationship (QSAR) between toxicity data and partition coefficient of the examined compounds could be modeled as follows: \textlog₁₀ \textEC₅₀   ( m\textM ) = - 0.6428  \textlog  P + 5.76  ( \textR² ? 0.88 ){\text{log}}_{{10}} {\text{EC}}_{{50}} \;{\left( {\mu {\text{M}}} \right)} = - 0.6428\;{\text{log}}\;P + 5.76\;{\left( {{\text{R}}^{2} \approx 0.88} \right)}. This indicates that the photosynthetic activity of the microalga Pseudokirchneriella subcapitata is highly dependent on the hydrophobicity of these commonly used organic solvents.     

Ecophysiology parameters of four Brazilian Atlantic Forest species under shade and drought stress

The Brazilian Atlantic Forest has experienced a reduction in its original area since the discovery of Brazil. Over the last 30 years, studies and techniques for forest recovery have advanced. Establishing a self-sustainable reforested area with adequate biodiversity is the main parameter for any reforestation program. Thus, knowledge of the ecophysiological behavior of the species to be used is crucial. Our hypothesis is that certain tools are efficient in determining the ecophysiological characterization of native species within different functional groups. Filling group plants show fast growth, intense gas exchange, present mechanisms of water deficit tolerance and show high efficiency in radiation capture, so they are first planted in a reforestation area. While plants pertaining to the diversity group do not exhibit these characteristics, thus are plants after the establishment of the first group of species. To test this hypothesis, two experiments were installed using young plants of four species native to the Atlantic Forest, grown in 9-L pots. Leaf water potential, gas exchange, chlorophyll fluorescence and certain biochemical parameters of leaf metabolism were evaluated. In the first experiment, plants were maintained under two forms of light availability for 15 days, full light (control) and shaded (shade). The species Inga sp. and Brosimum guianensis presented the most contrasting responses on day 15, principally in the variables leaf water potential, gas exchange, leaf soluble sugar content, F_\textv^￠ /F_\textm^￠ F_{\text{v}}^{\prime } /F_{\text{m}}^{\prime } and F _v/F _m. In the second experiment, plants were divided into two groups: a well-hydrated group (control) and one that underwent irrigation suspension for 7 days (drought); measurements were performed on day 8 of drought. Again, Inga sp. and Brosimum guianensis plants showed responses characterizing them as pertaining to distinct functional groups for the experimental parameters previously described. Thus, Inga sp. was classified as pertaining to the filling group and B. guianensis to the diversity group. The performance of the species Cinnamomum zeylancium and Tapirira guianensis under the conditions studied suggests that these are intermediate species with potential for use as filling group species.     

Effects of nitrate on intracellular nitrite and growth of Microcystis aeruginosa

Although nitrate is a macronutrient and can serve as good nitrogen source for many species of phytoplankton, high nitrate concentrations do not benefit the growth of phytoplankton. We hypothesise that algae cultured under high nitrate concentrations can accumulate intracellular nitrite, which is produced by nitrate reductase (NR) and can inhibit the growth of algae. To assess the validity of this hypothesis, Microcystis aeruginosa was grown under different nitrate concentrations from 3.57 to 21.43 mM in low CO₂ and high CO₂ conditions for 15 days. We observed that, with increasing nitrate concentrations, the intracellular nitrite concentrations of the alga increased and the growth rates and photosynthesis declined. When grown under high CO₂ conditions, M. aeruginosa showed lower intracellular nitrite concentrations and higher growth rates and \textP_\textm^\textchla {\text{P}}_{\text{m}}^{{\text{chl}}a} , \textR_\textd^\textchla {\text{R}}_{\text{d}}^{{\text{chl}}a} , α^chla than under low CO₂ conditions. These results suggest that the accumulation of intracellular nitrite could be the cause of inhibition of algal growth under high nitrate concentrations.     

Effects of environmental oxygen on development and respiration of Australian lungfish (<Emphasis Type="Italic">Neoceratodus forsteri</Emphasis>) embryos

The effects of oxygen partial pressure ( P_\textO2 P_{{{\text{O}}_{2} }} ) on development and respiration were investigated in the eggs of the Australian lungfish, Neoceratodus forsteri. At 20°C, embryonic survival and development was optimal at 15 and 20.9 kPa. Development was slowed at 5 and 10 kPa and embryos did not survive 2 kPa. At lower P_\textO2 P_{{{\text{O}}_{2} }} , the rate of oxygen consumption also decreased. Embryos responded to hypoxia by hatching at an earlier age and stage of development, and hatching wet and dry gut-free masses were reduced. The role of oxygen conductance ( G_\textO2 G_{{{\text{O}}_{2} }} ) in gas exchange was also examined under selected environmental P_\textO2 P_{{{\text{O}}_{2} }} and temperatures. The breakdown of the vitelline membrane changed capsule geometry, allowed water to be absorbed into the perivitelline space and increased capsule G_\textO2 G_{{{\text{O}}_{2} }} . This occurred at embryonic stage 32 under all treatments and was largely independent of both P_\textO2 P_{{{\text{O}}_{2} }} and temperature (15, 20 and 25°C), demonstrating that capsule G_\textO2 G_{{{\text{O}}_{2} }} cannot adaptively respond to altered environmental conditions. The membrane breakdown increased capsule diffusive G_\textO2 G_{{{\text{O}}_{2} }} and stabilised perivitelline P_\textO2 P_{{{\text{O}}_{2} }} , but reduced the convective G_\textO2 G_{{{\text{O}}_{2} }} of the perivitelline fluid, as the large perivitelline volume and inadequate convective current resulted in a P_\textO2 P_{{{\text{O}}_{2} }} gradient within the egg prior to hatch.