The utilization of lightflecks for growth in four Australian rain-forest species

1. The ability of rain-forest plants to utilize sunflecks for growth was investigated using the following species: Alocasia macrorrhiza, Diploglottis diphyllostegia, Micromelum minutum and Omalanthus novo-guinensis.
2. Growth analysis and gas-exchange measurements were used to assess performance of the four species when exposed to either constant or fluctuating light.
3. Final biomass (g dry wt) in D. diphyllostegia and M. minutum grown under the lightfleck regime (total daily PFD = 7·02 mol m^–2 day^–1) was significantly greater than in the same species grown under constant low PFD (total daily PFD = 4·86 mol m^–2 day^–1). In contrast, final biomass in lightfleck O. novo-guinensis and A. macrorrhiza was significantly reduced in comparison with the same species grown under constant low PFD.
4. When grown under either constant or fluctuating light but with the same total daily PFD, A. macrorrhiza and O. novo-guinensis had significantly lower final biomass in fluctuating light as compared to constant light. Final biomass in D. diphyllostegia was not significantly different in either regime, while M. minutum had significantly higher final biomass in the fluctuating light regime.
5. Responses of the four species to fluctuating or constant light appeared to be the result of physiological rather than morphological acclimation as net assimilation rate was more closely correlated with relative growth rate than was leaf area ratio.     

THE INTERACTION BETWEEN INORGANIC CARBON ACQUISITION AND LIGHT SUPPLY IN PALMARIA PALMATA (RHODOPHYTA)1

The dependence of the carbon concentrating mechanism of Palmaria palmata (L.) Kuntze on the growth light level was examined 1) to determine whether or not there is a threshold photon flux density (PFD) at which the inorganic carbon uptake mechanism can operate and 2) to attempt to quantify the relative energetic costs of acclimation to the two different limiting factors, PFD and dissolved inorganic carbon (DIC) concentration. Plants were grown at six PFDs: 5, 25, 50, 75, 95, and 125 μmol photons. m^?2.s^?1. Growth rates increased with increasing PFD from 5 to 50 μmol photons. m^?2. s^?1 and were light-saturated at 75, 95, and 125 μmol photons. m^?2. s^?1 Values of δ¹³C increased continuously with increasing growth PFD and did not saturate over the range of light levels tested. Time-resolved fluorescence characteristics indicated a progressive photoacclimation below 50 μmol photons. m^?2. s^?1. Analysis of chlorophyll fluorescence induction showed three levels of light use efficirncy associated with growth at 5 or 25, 50, and >75 μmol photons. m^?2. s^?1. The light-haruesting efficiency was inversely proportional to the effectiveness of DIC acquisition in plants grown at the six PFDs. These data were interpreted to indicate that there is a physiological tradeoff between photosynthetic efficiency and bicarbonate use in this species.     

INFLUENCE OF IRRADIANCE ON CELL VOLUME AND CARBON QUOTA FOR TEN SPECIES OF MARINE PHYTOPLANKTON1

Ten species of marine phytoplankton were grown under a range of photosynthetic photon flux densities (PFDs) and examined for variation in cell volume and carbon quota. Results suggest that in response to low PFDs phytoplankton generally reduce their cell volume and frequently reduce their carbon quota. A significant linear relationship between the log of PFD (I) and cell volume (in nine of ten species) and log I and carbon quota (four of ten species) was demonstrated. When exposed, to a transient in light intensity, Thalassiosira pseudonana (Hustedt, clone 3H) Hasle and Heimdal underwent a rapid adaptation in cell volume and carbon quota. Cells going from low light to high light reached maximum mean cell volume within 5 h, and cells going from high light to low light reached a minimum mean cell volume within 12 h. The resulting kinetic constant (k; a measure of the rate of adaptation) was considerably larger than previously reported k values. Ditylum brightwellii (West) Grunow increased in length but did not increase in width during a transient to increased irradiance. Nutrient limitation was shown to override PFD in determining cell volume and carbon quota for Heterosigma akashiwo Hada. Cells grown at equivalent irradiances but N-limited, were smaller than light-limited and nutrient-saturated cells. Therefore, cell volume and carbon quota do not have the same relationship with PFD when factors other than PFD control growth rate. The ecological implications of reduced cell volumes and carbon quotas with decreasing PFD include possible impacts on CO₂ budgets, an influence on sinking rates, potential changes in predation rates, and surface area/cell volume benefits.     

Responses of Rubisco activation and deactivation rates to variations in growth-light conditions

Basil (Ocimum basilicum) and impatiens (Impatiens wallerana) were grown in sun, shade, or fluctuating light (15 min sun, 15 min shade) to examine the effects of growth-light conditions on the rates of light-induced Rubisco activation and deactivation. Rubisco activation and deactivation rates were determined from gas-exchange measurements of photosynthesis following a step increase in PFD. Rubisco deactivation rates were also determined from biochemical analyses of leaf extracts. There were no significant differences in Rubisco activation rate among the growth conditions or between the two species. However, there were significant differences in Rubisco deactivation rate among the growth conditions in basil and between the two species. In basil, Rubisco deactivated more slowly following a decrease in PFD in sun- and fluctuating-light grown plants than in shade grown plants. Slower rates of Rubisco deactivation during periods at low PFD resulted in higher activation states at the onset of increased PFD. Thus, the contribution of Rubisco activation to the induction process was less for basil plants grown under sun and fluctuating light than for those grown under shade. Impatiens deactivated Rubisco more rapidly than in basil, but there was no substantial effect of the three growth-light conditions on Rubisco deactivation rates in impatiens.     

Growth of Rhodopseudomonas capsulata on l- and d-malic acid

d-malate replaced l-malate in supporting both photosynthetic (anaerobic, light) and heterotrophic (aerobic, dark) growth of Rhodopseudomonas capsulata. Growth rates and cell yields were nearly equivalent with both enantiomorphs. Addition of glucose to malate culture media increased the growth rate and doubled the cell yield of heterotrophic cultures, but had little effect on photosynthetic cultures. Aerobically-grown cells showed a higher level of substrate-dependent oxygen uptake with l-malate than with d-malate. This preference for l-malate occured even in cells grown on d-malate. No malic racemase activity was detected in extracts of heterotrophically- or photosynthetically-grown cells.     

Effect of photoperiod and light intensity on in vitro propagation of Alocasia amazonica

Plantlets of Alocasia amazonica regenerated under a photon flux density (PFD) of 15 or 30 μmol m⁻² s⁻¹ showed better growth and development than those grown under higher PFDs. While chlorophyll a and chlorophyll b decreased, the number of stomata increased with increasing PFD. Photoperiods also affected plantlet growth and stomatal development. Highest growth was observed for the short photoperiod (8/16 h) and for equinoctial (12/12 h) light and dark periods. Very few stomata developed in the leaves of plantlets grown under a short photoperiod (8/16 h) and the number of stomata increased with increasing light period. In conclusion, both light intensity and photoperiod independently affect growth of A. amazonica and development of stomata, depending on the intensity and duration of light treatment.     

LIGHT DEPENDENCE OF GROWTH AND PHOTOSYNTHESIS IN PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1

Phaeodactylum tricornutum Bohlin was maintained in exponential growth over a range of photon flux densities (PFD) from 7 to 230 μmol·m^?2s^?1. The chlorophyll a-specific light absorption coefficient, maximum quantum yield of photosynthesis, and C:N atom ratio were all independent of the PFD to which cells were acclimated. Carbon- and cell-specific, light-satuated, gross photosynthesis rates and dark respiration rates were largely independent of acclimation PFD. Decreases in the chlorophyll a-specific, gross photosynthesis rate and the carbon: chlorophyll ratio and increases of cell- or carbon-specific absorption coefficients were associated with an increase in cell chlorophyll a in cultures acclimated to low PFDs. The compensation PFD for growth was calculated to be 0.5 μmol·m^?2s^?1. The maintenance metabolic rate (2 × 10^?7s^?1), calculated on the basis of the compensation PFD, is an order of magnitude lower than the measured dark respiration rate(2.7 × 10^?6mol O₂·mol C^?1s^?1). Maintenance of high carbon-specific, light-saturated photosynthesis rates in cells acclimated to low PFDs may allow effective use of short exposures to high PFDs in a temporally variable light environment.     

The Xanthophyll Cycle in Intermittent Light-Grown Pea Plants (Possible Functions of Chlorophyll a/b-Binding Proteins)

The xanthophyll cycle in pea (Pisum sativum L. cv Kleine Rheinlanderin) plants has been investigated in vivo. Control plants were compared with those grown under intermittent light (IML plants). IML plants are particularly characterized by the absence of nearly all chlorophyll a/b-binding proteins. The rates of de-epoxidation during 30 min of illumination and their dependence on the incident photon flux density (PFD) have been determined. They were very similar in both types of plants, with the exception that IML plants contained, at any PFD, much higher zeaxanthin concentrations in the steady state (reached after about 15 min of illumination) than control plants. This indicates that the amount of convertible violaxanthin under illumination is dependent on the presence of chlorophyll a/b-binding proteins. The epoxidation rate (examined at a PFD of 15 [mu]E m-2 s-1, after 15 min of preillumination with different PFDs) showed significant differences between the two types of plants. It was about 5-fold slower in IML plants. On the other hand, in both types of plants, the epoxidation rate decreased with increasing PFD during preillumination. Prolonged preillumination at high PFDs resulted in a decrease of the epoxidation rate without a further increase of the zeaxanthin concentration in both continuous light and IML plants. This result argues against a permanent turnover of the xanthophylls under illumination, at least at high PFDs.     

Effects of temperature, irradiance, and daylength on the marine diatom Leptocylindrus danicus Cleve. IV. Growth

Growth and dark respiration rates of the marine diatom Leptocylindrus danicus Cleve were measured in axenic batch culture under 49 combinations of temperature (5, 10, 15, 20°C), daylength(15:9, 12:12, 9:15 LD), and irradiance (at least four irradiances per daylength). Cell division rates exhibited a temperature-dependent daylength effect. Optimal temperatures occurred between 15 and 20°C. Both the initial slope () and the growth rate at light saturation (μ_max) were strongly influenced by temperature; increased five-fold and μ_max by an order of magnitude between 5 and 20°C. The compensation irradiance (I_c) was independent of temperature. μ_max was 2.7 div day⁻¹ at 20°C, 2.6 at 15°C, 1.1 at 10°C, and 0.3 at 5 °C. Cells grown under 15:9 and 12:12 LD exhibited similar growth-light curves at 20°C and at 15°C. μ_max of cells grown under 9:15 LD at these temperatures were substantially lower than μ_max under longer daylengths. Growth at 10 and 5°C was independent of daylength.

Dark respiration rates were a linear function of cell division rates at 10, 15, and 20°C, and support the concept that growth rate is dependent on dark respiration rate. These relationships were not influenced by daylength. A detectable relationship between dark respiration and growth at 5°C was not observed.

Photosynthesis and excretion showed temperature-dependent curvilinear relationships with growth rate, reflecting the lower saturation irradiance for growth compared to light saturation of photosynthesis and excretion. The relationship between Chl a-specific photosynthesis and growth was controlled by the C:Chl a ratio, which showed a positive correlation with cell division rate. At 15 and 20°C, light saturation of growth was associated with C:Chl a ratios of 40 to 60; at 5 and 10°C, cells growing at μ_max contained C:Chl a in ratios of 80 to 110.     

COMPARATIVE PHYSIOLOGICAL STUDY OF MARINE DIATOMS AND DINOFLAGELLATES IN RELATION TO IRRADIANCE AND CELL SIZE. II. RELATIONSHIP BETWEEN PHOTOSYNTHESIS,GROWTH, AND CARBON/CHLOROPHYLL a RATIO1,2

Photosynthetic rates, growth rates, cell carbon, cell protein, and chlorophyll a content of two diatom and two dinoflagellate species were measured. The microalgae were chosen to have one small and one large species from each phylogenetic group; the two size categories differed from each other by 1.5 orders of magnitude in terms of cell carbon or cell protein. The cultures for the experiments were grown under continuous light at an irradiance high enough for the light-saturation of growth for all four species. The four species were found to have similar maximum photosynthetic rates per unit chlorophyll a. The diatom species showed lower carbon/chlorophyll a ratios and higher photosynthetic rates per unit carbon than the dinoflagellates. The higher growth rates of the diatoms were shown to be related to their higher photosynthetic rates per unit carbon. The ecological significance of the physiological difference between these two groups of microalgae is discussed.     

A moss “canopy” – Small-scale differences in microclimate and physiological traits in Tortula ruralis

We studied vertical changes in light regime and water content (WC) in combination with vertical gradients in several physiological response variables, i.e. net CO₂ uptake, chlorophyll content and nitrogen content in the moss species, Tortula ruralis. The rate of light attenuation within the moss turf, which was determined with a custom-made optical microprobe system, was strongly dependent on plant WC. Curling movements of the upper leaves associated with the beginning desiccation of the uppermost parts of a turf allowed increased penetration of light to greater depth with decreasing WC. The capacity to fix carbon declined steeply with depth: below ca. 9 mm no net CO₂ uptake occurred, even when removing the shading parts above. The potential rates of photosynthesis in different depths were highly correlated with chlorophyll content, but not nitrogen content.     

RESPONSE OF PROROCENTRUM MARIAE-LEBOURIAE (DINOPHYCEAE) TO LIGHT OF DIFFERENT SPECTRAL QUALITIES AND IRRADIANCES: GROWTH AND PIGMENTATION1

Growth and pigment concentrations of the, estuarine dinoflagellate, Prorocentrum mariae-lebouriae (Parke and Ballantine) comb. nov., were measured in cultures grown in white, blue, green and red radiation at three different irradiances. White irradiances (400–800 nm) were 13.4, 4.0 and 1.8 W · m^?2 with photon flux densities of 58.7 ± 3.5, 17.4 ± 0.6 and 7.8 ± 0.3 μM quanta · m^?2· s^?1, respectively. All other spectral qualities had the same photon flux densities. Concentrations of chlorophyll a and chlorophyll c were inversely related to irradiance. A decrease of 7- to 8-fold in photon flux density resulted in a 2-fold increase in chlorophyll a and c and a 1.6- to 2.4-fold increase in both peridinin and total carotenoid concentrations. Cells grown in green light contained 22 to 32% more peridinin per cell and exhibited 10 to 16% higher peridinin to chlorophyll a ratios than cells grown in white light. Growth decreased as a function of irradiance in white, green and red light grown cells but was the same at all blue light irradiances. Maximum growth rates occurred at 8 μM quanta · m^?2· s^?1 in blue light, while in red and white light maximum growth rates occurred at considerably higher photon flux densities (24 to 32 μM quanta · m^?2· s^?1). The fastest growth rates occurred in blue and red radiation. White radiation producing maximum growth was only as effective as red and blue light when the photon flux density in either the red or blue portion of the white light spectrum was equivalent to that of a red or of blue light treatment which produced maximum growth rates. These differences in growth and pigmentation indicate that P. mariae-lebouriae responds to the spectral quality under which it is grown.     

Trypanosoma theileri: In vitro cultivation in tsetse fly and vertebrate cell culture systems

Epimastigote forms of Trypanosoma theileri were grown at 25°C in insect cell culture media and in Glossina tissue cultures for more than 6 months. Doubling times of 10–14 h during exponential growth were observed. In cell cultures which had been derived from pupal tsetse flies growth rates were higher than in cell free media; in a larval cell line, however, growth of T. theileri was inhibited. Ecdysteroids and juvenile hormone I reduced multiplication of T. theileri in cell free media. When T. theileri was incubated in different sera only fetal calf serum (FCS) supported growth. Epimastigote forms transformed into trypomastigote bloodforms when cultured at 37°C in FCS, vertebrate cell cultures, and Eagle's medium, but not in insect media or Glossina cell cultures. Oxygen uptake of epimastigotes could be inhibited by rotenone antimycin A and cyanide; trypomastigotes were not affected by these inhibitors.     

Growth of Rhodopseudomonas capsulata on l- and d-malic acid

d-malate replaced l-malate in supporting both photosynthetic (anaerobic, light) and heterotrophic (aerobic, dark) growth of Rhodopseudomonas capsulata. Growth rates and cell yields were nearly equivalent with both enantiomorphs. Addition of glucose to malate culture media increased the growth rate and doubled the cell yield of heterotrophic cultures, but had little effect on photosynthetic cultures. Aerobically-grown cells showed a higher level of substrate-dependent oxygen uptake with l-malate than with d-malate. This preference for l-malate occured even in cells grown on d-malate. No malic racemase activity was detected in extracts of heterotrophically- or photosynthetically-grown cells.     

Unusual allometry between in situ growth of freshwater phytoplankton under static and fluctuating light environments: possible implications for dominance

The effects of fluctuating light fields on the growth of phytoplanktonare not well understood and conclusions in the literature havebeen equivocal. Most studies have examined responses such asproductivity and chlorophyll a content (laboratory culture andfield tests) or growth rates (laboratory culture tests). Inthis study we examined the in situ growth rates of differenttypes of phytoplankton within two natural populations. Comparisonswere made between populations grown in a static environment(suspended in a fixed position in the water column) and an equivalentpopulation moving through the water column simulating the mixingof entrained phytoplankton. Growth under fluctuating light fieldsin this experiment only significantly (P < 0.05) increasedthe growth of the diatom Skeletonema and decreased the growthof Anabaena circinalis, Microcystis aeruginosa and Scenedesmussp. All other phytoplankton, including the genera Nitzschia,Fragilaria and Dactylococcopsis, did not have growth rates thatwere significantly different between static and fluctuatinglight treatments. A general pattern where diatoms grew best,followed by chlorophytes with the toxicogenic cyanophytes M.aeruginosa and A. circinalis growing least well, was distinguishedunder fluctuating irradiance. This seems consistent with thecommon occurrence of these groups of phytoplankton in the naturalenvironment. The cyanophytes Dactylococcopsis and Aphanothecedid not follow this pattern, with the former growing betterunder fluctuating light and the latter exhibiting an unusualgrowth pattern where growth was higher under lower light intensities.     

Response of corn to combinations of atrazine, propyl gallate and ozone

Growth chamber experiments were conducted to determine the influence of the air pollutant ozone (O₃) [0.2 and 0.3 ppm (v/v)] on the growth of corn (Zea mays L.) treated with the herbicide atrazine (2.5 and 3.5 kg/ha) and the antioxidant propyl gallate (5 and 8 kg/ha). At both concentrations O₃ at 0.3 ppm alone reduced dry weights of corn and chlorophyll. Chlorophyll a was more affected than chlorophyll b by O₃ at 0.3 ppm alone and in combination with atrazine. Propyl gallate at both rates protected corn against O₃ injury. The interaction between atrazine and O₃ at 0.2 ppm was additive whereas at 0.3 ppm it was antagonistic. But combinations of atrazine and propyl gallate did not protect corn from O₃ injury.     

Growth of the sponge Pseudosuberites (aff.) andrewsi in a closed system

Explants of the Indo-Pacific sponge Pseudosuberites aff. andrewsi were fed with the microalgae Chlorella sorokiniana and Rhodomonas sp. It was microscopically observed that these algae were ingested and digested by the sponge cells, suggesting that they were consumed by the sponges. The algae were further used for two growth experiments with five explants of P. aff. andrewsi and four explants of P. andrewsi. Growth was measured as the increase in projected body area. The explants showed considerable growth (up to 730% in 54 days for P. aff. andrewsi and up to 680% in 22 days for P. andrewsi), which is much higher than previously reported growth rates for sponges. Growth started after a stationary phase of 5–20 days in which the projected body area did not increase. The growth of P. aff. andrewsi appeared to be linear and was inhibited at the end of the experiment. Two explants of P. andrewsi showed exponential growth instead of linear growth. Hence, no general statements about the growth kinetics of these sponges can be made at this time. However, the high growth rates found in this study suggest a promising future for cultivation of sponges in closed systems.     

表达透明颤菌血红蛋白基因对酿酒酵母生长及细胞内氧化状态的影响*

透明颤菌血红蛋白基因vgb在多种研究和工业发酵菌中异源表达很好的解决了高密度发酵中的溶氧率问题。酿酒酵母是经典的真核模型,且在发酵工业中具有重要的应用价值,但vgb在酿酒酵母中异源表达对细胞生长的影响并不清楚。以ADH1为启动子构建了含透明颤菌(Vistreoscilla)血红蛋白基因vgb的异源表达质粒YEplac195-ADH1pr-vgb,并转化至酿酒酵母BY4741。通过生长敏感性实验,发现在发酵碳源和非发酵碳源中,vgb的异源表达均抑制了菌株生长。接着,通过2',7'-二氯荧光黄双乙酸盐和PI染色和脂质过氧化产物检测分析,发现过表达vgb的酿酒酵母细胞中活性氧(ROS)的积累、细胞膜通透性改变以及脂质过氧化。结果表明,酿酒酵母中过表达vgb改变细胞的氧化状态促进活性氧的累积,氧化应激导致菌株的生长抑制。     

Chlorophyll formation and the development of photosynthesis in dark grown seedlings of Picea abies

Abstract Seeds of Picea abies were germinated and grown in either darkness or constant light. The chlorophyll content and photosynthetic carbon dioxide uptake of developing seedlings of different ages was determined. Ten-day-old dark grown seedlings showed an instant ability for photosynthetic carbon dioxide uptake and also formed further chlorophyll most rapidly upon subsequent illumination. These activities progressively diminished when the dark growth period was extended. Light grown seedlings reached a maximum chlorophyll level after 15 days growth, and this preceded maximal photosynthetic development.     

Marine Plankton Algae Grown with Light-Dark Cycles.

The diatoms Ditylum brightwellii and Nitzschia turgidula were grown in semi-continuous culture under various combinations of light intensity, temperature and daylength (photoperiod). Growth was strongly limited by light intensities below 0.03 cal/em². min in both species. Above this intensity, light saturation of growth was rapidly approached in Nitzschia but only gradually so in Ditylum. The growth rate in continuous light was never significantly higher than with 16 hours of light plus 8 hours of dark. In Ditylum, continuous light above 0.03 cal/cm². min caused a strong inhibition of growth at all temperatures. The chlorophyll concentration in the cells was greater the shorter the photopceriod. In cultures synchronised by different combinations of light intensity and photoperiod, cell division generally took place in the light. Synchrony was best under short photoperiods of bright light. Time courses are shown for chlorophyll synthesis and photosynthesis in synchronised cultures.