Effect Of Photon Flux Density Research Articles

Empirical operating strategy to reduce the light-specific energy consumption of a flat-panel airlift photobioreactor with intrinsic static mixers cultivating Thermosynechococcus elongatus BP-1

During photoautotrophic cultivations using optimized synthetic media, light is the limiting “substrate” of high-density cultures, especially throughout outdoor cultivations prohibiting adjustment of photon-flux density (PFD). Convective mass transfer (turbulence) is the method of choice to cope with that limiting effect. Then again, turbulence comes at costs through the energy required for its generation. In this context and based on laboratory data generated with Thermosynechococcus elongatus BP-1, an empiric operating strategy for flat-panel airlift photobioreactors with intrinsic static mixers is suggested. Repeated cultivations were performed from sub- to supra-saturating PFD (180 to 780μmolm−2s−1) at aeration rates ranging from 0.11 to 0.83vvm assessing the cultures' productivities along the courses of biomass concentrations. The results indicate that, owing to the culture-flow directing mixers, there is a strong interrelation between the effects of PFD, biomass concentration and aeration rate (thus energy input) applied. Hereby, the positive impact of directed turbulence on the cultures' performance with respect to productivity and yield was greatest at high biomass concentration (>5gDWL−1) and PFDs with effects becoming less dominant while the latter two were reduced. Based on the quantitative findings and utilizing the easily monitored parameters PFD and biomass concentration, a computational model may be defined automatically controlling the easily adjustable parameter aeration rate. Without a negative influence on cultures' performance, this will allow for both, increase of culture performance at times of intense light and high biomass concentration as well as reduction of operational expenditures (OPEX) at times of dim light or low biomass concentration. Compared to the standard, continuous aeration regime, this may lead to a reduction of energy required for the generation of turbulence of 37%, especially when considering outdoor cultivations in temperate climate zones.

Optimizing LED lighting for space plant growth unit: Joint effects of photon flux density, red to white ratios and intermittent light pulses

The aim of this work were to choose a quantitative optimality criterion for estimating the quality of plant LED lighting regimes inside space greenhouses and to construct regression models of crop productivity and the optimality criterion depending on the level of photosynthetic photon flux density (PPFD), the proportion of the red component in the light spectrum and the duration of the duty cycle (Chinese cabbage Brassica сhinensis L. as an example). The properties of the obtained models were described in the context of predicting crop dry weight and the optimality criterion behavior when varying plant lighting parameters. Results of the fractional 3-factor experiment demonstrated the share of the PPFD level participation in the crop dry weight accumulation was 84.4% at almost any combination of other lighting parameters, but when PPFD value increased up to 500µmol m−2s−1 the pulse light and supplemental light from red LEDs could additionally increase crop productivity. Analysis of the optimality criterion response to variation of lighting parameters showed that the maximum coordinates were the following: PPFD = 500µmol m−2s−1, about 70%-proportion of the red component of the light spectrum (PPFDLEDred/PPFDLEDwhite = 1.5) and the duty cycle with a period of 501µs. Thus, LED crop lighting with these parameters was optimal for achieving high crop productivity and for efficient use of energy in the given range of lighting parameter values.

The effect of photon flux density on algal biofilm growth and internal fatty acid concentrations

Algal biofilm systems offer potential advantages over planktonic systems for growing, harvesting and processing algal biomass. To determine how feasible these systems can be, however, researchers must determine optimal biomass and lipid productivities. In this paper the effect of photon flux density (PFD) on algal biofilm biomass productivities, internal fatty acid concentrations, and overall fatty acid productivity was studied. It was determined that as PFD increased, algal biofilm biomass productivities significantly increased until they peaked i.e. at about 300μmol/m2/s, presumably due to light saturation. Increasing PFDs from 50 to 150μmol/m2/s produced statistically significant increases in fatty acid concentrations from 5% to 8%; however, increasing PFDs beyond that range did not enhance lipid accumulation. Because of significant increases in biomass productivity with increased PFD, there was also a significant increase in fatty acid productivity with increased PFD. Lastly, increasing PFD resulted in diminishing returns of biomass productivity, suggesting that photons are not being effectively utilized at higher light intensities. This finding has implications for photobioreactor design and operation with artificial lighting.

The Effect of Photon Flux Density and Lighting Period on Growth, Flowering, Powdery Mildew and Water Relations of Miniature Roses

Miniature roses (Rosa sp.) were grown at 100 and 150 μmol m-2·s-1 photon flux densities (PFD) with 16, 20 and 24 h·day-1 lighting periods (LP) in a greenhouse compartment in midwinter at latitude 59° north. The study included 10 different treatments and six rose cultivars, altogether 900 plants. The 16 and 20 h LP were applied with or without a dark period of 8 and 4 h·day-1, respectively, by timing the LP in relation to daylight that lasted for 7 - 8 h. Number of days until flowering decreased with an increase in PFD and in LP up to 24 day-1 and was unaffected by the timing of the 16 and 20 h·day-1 LP. Number of flowers and plant dry weight increased 20% to 30% by increasing the PFD. Plant dry weight increased by increasing the LP from 16 to 20 h·day-1 (about 25%), but no effect was found with a further increase to 24 h·day-1. Mean growth rate until flowering increased 30% to 40% by increasing the PFD or by increasing the LP from 16 to 20 h day-1, while little effect was found by a further increase to 24 h·day-1. Increasing the photosynthetic active radiation (PAR) by increasing the LP from 16 to 20 h·day-1 increased the growth rate more than increasing the PFD did. Three of the cultivars were tested for water loss after the detachment of some leaves. Leaves that had developed without a dark period showed a considerably higher water loss than the treatments that included a dark period of 4 or 8 h·day-1. The keeping quality at indoor conditions, however, was unaffected by the treatment due to sufficient watering. Powdery mildew developed significantly more on plants grown with a dark period of 8 h as compared with the other treatments. It was concluded that 20 h·day-1 LP including a dark period of 4 h·day-1 and a PFD of at least 150 μmol·m-2·s-1 should be applied to miniature roses during the winter months in order to effectively produce miniature pot roses with a high quality.

The Effect of Photon Flux Density and Module Temperature on Power Output of Photovoltaic Array

This article presents the effects of photon flux density and module temperature on power output of amorphous silicon (a-Si), polycrystalline (p-Si) and hetero-junction intrinsic thin layer (HIT) photovoltaic (PV) modules under Thailand climatic condition which located at the equator zone. The outdoor solar irradiance distribution measurements on the PV array installed at Energy Park, School of Renewable Energy Technology (SERT), Naresuan University, Thailand revealed that the solar irradiance is directly proportional with photon flux density which the wavelength is influence of photon flux density. The increasing of power output under real working of a-Si and p-Si depends on both photon flux density and module temperature. But the increasing of power output of HIT mainly depends on both photon flux density.

Dependence of Noise Properties on Photon Flux Incident on Silicon MITATT Device at Millimeter-Wave Window Frequencies

The effect of photon flux density on the noise properties of optically illuminated Double Drift Region (DDR) Mixed Tunneling Avalanche Transit Time (MITATT) device is investigated in this paper. An analytical model is proposed to obtain a relationship between the normalized difference of electron and hole current density of DDR device and the incident photon flux on it. Simulation is carried out to study the small signal noise spectral density and noise measure of the device under optical illumination. Two illumination configurations i.e., Flip Chip (FC) and Top Mounted (TM) structures are considered in the simulation. The device is designed to operate at mm-wave window frequency at W-band. The results show that avalanche noise measures of FC and TM structures of photo irradiated device are 37.1 dB and 40.2dB respectively for an incident photon flux density of 1024 m-2 sec-1 at 1000nm wavelength near band gap absorption of Silicon. The noise measure of the un-illuminated device is found to be 35dB. The results indicate that the increase of avalanche noise due to the incident photon flux can be reduced if FC structure is taken instead of TM structure.

Effect of photon flux densities on regulation of carotenogenesis and cell viability of Haematococcus pluvialis (Chlorophyceae).

The green alga Haematococcus pluvialis produces large amounts of the pink carotenoid astaxanthin under high photon flux density (PFD) and other oxidative stress conditions. However, the regulation and physiological role of carotenogenesis leading to astaxanthin formation is not well understood. Comparative transcriptional expression of five carotenoid genes along with growth and pigment composition as a function of PFD was studied using a wild-type and an astaxanthin-overproduction mutant of H. pluvialis NIES144. The results indicate that astaxanthin biosynthesis was mainly under transcriptional control of the gene encoding carotenoid hydroxylase, and to a lesser extent, the genes encoding isopentenyl isomerase and phytoene desaturase, and to the least extent, the genes encoding phytoene synthase and carotenoid oxygenase. The expression of a plastid terminal oxidase (PTOX) gene ptox2 underwent transient up-regulation under elevated PFDs, suggesting that PTOX may be functionally coupled with phytoene desaturase through the plastoquinone pool and may play a role in reducing redox-potential-dependent and oxygen-concentration-dependent formation of reactive oxygen species in the chloroplast. Over-expression of both the carotenogenic and PTOX genes confers to the astaxanthin-overproduction mutant more effective photoprotective capability than that of the wild type under photooxidative stress.

Light and CO2 do not affect the mesophyll conductance to CO2 diffusion in wheat leaves

In C(3) plants, diffusion of CO(2) into leaves is restricted by stomata and subsequently by the intercellular airspaces and liquid phase into chloroplasts. While considerable information exists on the effect of environmental conditions on stomatal conductance (g(s)), little is known on whether the mesophyll conductance to CO(2) diffusion (g(m)) changes with respect to photon flux density (PFD) and CO(2) partial pressure (pCO(2)). In this study, the effects of PFD and/or pCO(2) on g(m) were examined in wheat leaves by combining gas exchange with carbon isotope discrimination measurements using a membrane inlet mass spectrometer. Measurements were made in 2% O(2) to reduce the fractionation associated with photorespiration. The magnitude of g(m) was estimated using the observed carbon isotope discrimination (Delta), ambient and intercellular pCO(2), CO(2) assimilation and respiration rates, either from an individual measurement made under one environmental condition or from a global fit to multiple measurements where PFD was varied. It was found that respiration made a significant and variable contribution to the observed discrimination, which associated with the difference in isotopic composition between CO(2) in the greenhouse and that used for gas exchange measurements. In wheat, g(m) was independent of PFD between 200 and 1500 micromol m(-2) s(-1) and was independent of p(i) between 80 and 500 microbar.

Effects of photon flux density and agricultural fertilizers on the development of Sarcothalia crispata tetraspores (Rhodophyta, Gigartinales) from the Strait of Magellan, Chile

Effects of photon flux density and agricultural fertilizers on the development of Sarcothalia crispata tetraspores (Rhodophyta, Gigartinales) from the Strait of Magellan, Chile

Effects of photon flux density on the morphology, photosynthesis and growth of a CAM orchid, Doritaenopsis during post-micropropagation acclimatization

Micropropagated plantlets are fragile and often lack sufficient vigour to survive the acclimatization shock during transplantation to the soil. Effects of photosynthetic photon flux densities (PPFDs) on growth, photosynthesis and anatomy of micropropagated Doritaenopsis were studied after 4 months of acclimatization in a greenhouse at 25 °C. The plantlets were transferred to three different PPFDs for four months, i.e. ‘low light’ (175), ‘intermediate light’ (270) and ‘high light’ (450 μmol m−2 s−1). For most of the growth parameters measured i.e. leaf length, leaf area, leaf width, fresh weight, dry weight, chlorophyll (Chl) a/b ratio, were greater for the intermediate light levels after 4 months of acclimatization. The only exception was leaf thickness, which was increased more under high light levels. Results showed that the survival of Doritaenopsis plantlets was greatest (90%) in low light and intermediate light (89%) compared with only (73%) at high light. However, at low light levels, pigment concentrations (chlorophyll a, b and total chlorophyll) were higher. Net CO2 assimilation (A), stomatal conductance (g) and transpiration (E) were higher in plantlets grown at high level PPFD than at low after 4 months of acclimatization. Photosynthetic efficiency (Fv/Fm) decreased insignificantly; only at mid day for the high light treatment whereas leaf temperature and stomatal closure increased compared to low light. Scanning electron microscopic (SEM) images of leaves from acclimatized plantlets showed an increase in wax formation for the high light grown plantlets compared to those at low light. Microscopic analysis of acclimatized root sections showed highly developed multiseriate-velamen layers and higher root cell activity; while shoots had larger leaf air spaces than those of in vitro grown plantlets. These results suggest that physiological acclimation occurs at the intermediate PPFD (270 μmol m−2 s−1) in Doritaenopsis compared to treatment at the high light level.

Photosynthetic responses of muskmelon (Cucumis melo L.) to photon flux density, leaf temperature and CO2 concentration

Two cultivars (Huanghemi and Elizabeth) of muskmelon (Cucumis melo L.) were evaluated to determine the effect of photon flux density (PFD), leaf temperature, and CO,2 concentration on the net photosynthetic rate (Pn). The cultivars were evaluated under open field and solar-heated greenhouse conditions in northwest China. The Pn increased as the PFD increased, and then the rate of increase in Pn declined for Huanghemi and decreased for Elizabeth. Elizabeth registered 22 µmol m-2 s-1 for light compensation and 1127 µmol m-2 s-1 for light saturation, which, respectively, were 50 and 70% of those required by Huanghemi. The Pn increased with increasing leaf temperatures in the range of 9.8 to 50.8°C. The optimum temperature for photosynthesis was 35.3°C for muskmelon grown in open field, 2.4°C (7%) greater than that for muskmelon grown in the greenhouse. At optimal temperatures, the field-grown muskmelon had the Pn of 19.8 µmol m-2 s-1, 30% greater than that for the greenhouse-grown muskmelon. Both cultivars responded positively to CO2 concentrations of below the CO2 saturation points, whereas Huanghemi exhibited greater (51%) Pn and higher (49%) carboxylation efficiency than Elizabeth at optimal CO2 level. The two cultivars exhibited greater photosynthesis in open field than when grown in solar-heated greenhouses, while Elizabeth performed better than Huanghemi when light conditions were poor. Selective use of cultivars with low requirements for light and temperatures will enhance the photosynthesis and productivity of muskmelon grown in solar-heated greenhouses of northwest China. Key words: Light compensation, light saturation, photon flux density, transpiration

Paraheliotropism in two Phaseolus species: combined effects of photon flux density and pulvinus temperature, and consequences for leaf gas exchange

Phaseolus species exhibit paraheliotropic (light-avoiding) leaf movements in response to environmental stimuli. We investigated the response of two ecologically contrasting species, Phaseolus vulgaris (mesic) and Phaseolus acutifolius (xeric), to various combinations of photosynthetic photon flux density (PFD) and pulvinus temperature to compare the control and consequences, in terms of photosynthetic gas exchange, of paraheliotropism under identical conditions. Leaflet angles were measured in a cuvette that exposed the leaf to controlled PFD and pulvinus temperature. A gas exchange system was used to determine carbon assimilation, stomatal conductance and water use efficiency (WUE) in response to environmental factors and leaf movements. The effect of tilting leaves was compared with an equivalent reduction of PFD for horizontal leaves. Both species showed significant (but different) responses to PFD and temperature, with increased light avoidance at high levels of both factors. P. acutifolius exhibited greater light avoidance under equivalent conditions. The gas exchange consequences of changing leaf angles were similar but not identical to those of an equivalent modification of radiation level. The photosynthetic cost of the leaf movements was negligible, but there was a substantial increase in WUE, especially for P. acutifolius. Thus, the benefits of paraheliotropism are achieved at virtually no cost to the plant.

Photon flux density dependence of carbon acquisition and demand in relation to shoot growth of kiwifruit (Actinidia deliciosa) vines grown in controlled environments

Kiwifruit [Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson] vines were grown in four controlled photon flux densities (PFDs) from 250 to 1100 µmol m –2 s –1 for 130 d starting from pre-budbreak to measure relationships between shoot growth and carbon (C) demand and to assess the effect of PFD on these processes. Leaf area, stem length, photosynthesis and respiration rates were measured on the same leaves at regular intervals. From daily C acquisition and accumulation in biomass, the net C balance per cane was determined throughout the experiment. High-PFD-grown vines had 13% more leaf area, 250% more leaf biomass and 30% more stem biomass than low-PFD-grown vines. High-PFD-grown vines also partitioned relatively more biomass to photosynthetic tissue than to supporting stem tissue compared with low-PFD-grown vines. Rates of net photosynthesis were highest on vines grown at 800 µmol m –2 s –1 , but respiration rates were highest in high-PFD-grown vines. Vines grown at 1100 µmol m –2 s –1 had a net gain of 119 g sh –1 and 53 g sh – at 250 µmol m –2 s –1 , of which 46 and 58%, respectively, was used in shoot biomass growth. Net C balance was negative for 30 d after budbreak. Over 130 d, high-PFD-grown vines produced a total surplus of 64 g sh –1 , while low-PFD-grown vines produced 22 g sh –1 . Results demonstrate that irradiance has no effects on developmental processes but has marked effects on vegetative growth rates of kiwifruit vines. Underlining this, the C economy of these shoots is highly and quantitatively dependent on the PFD during growth.

Elevated CO2 concentration has independent effects on expansion rates and thickness of soybean leaves across light and nitrogen gradients

The rate and extent of leaf thickness and area development are important determinants of whole plant photosynthetic capacity. The interactive effects of photon flux density (PFD), nitrogen supply and CO 2 concentration on leaf expansion rate were measured as well as final leaf size and thickness of soybean. Leaf thickness and final area were not correlated with leaf relative expansion rate (RER) suggesting that these parameters are controlled by different mechanisms and that final leaf dimensions are determined by the duration rather than the rate of leaf expansion. Carbohydrate supply did not explain the variation in leaf RER since RER increased with increasing CO 2 concentration, but decreased with increasing PFD. Leaf thickness and final area were related to resource supply but not in a simple fashion. Both positive and negative correlations between leaf thickness and carbohydrate and nitrogen concentrations were obtained depending on the environmental variable responsible for the variation. In contrast, there was a simple proportional relationship between whole plant relative growth rate and a correlate of leaf thickness (leaf water content per unit area), suggesting that leaf thickness responds to the balanced supply of all resources, in the same fashion as RGR, rather than to any individual resource.

Leaf nitrogen distribution in relation to leaf age and photon flux density in dominant and subordinate plants in dense stands of a dicotyledonous herb.

We studied the effects of photon flux density (PFD) and leaf position, a measure of developmental age, on the distribution of nitrogen content per unit leaf area (N area) in plants of different heights, in dense stands grown at two nitrogen availabilities and in solitary plants of the erect dicotyledonous herb Xanthium canadense. Taller more dominant plants received higher PFD levels and experienced a larger difference in relative PFD between their youngest and oldest leaves than shorter subordinate plants in the stands. Differences in PFD between leaves of solitary plants were assumed to be minimal and differences in leaf traits, found for these plants, could thus be mainly attributed to an effect of leaf position. In the solitary plants, N area decreased with leaf position while in the plants from the stands it decreased with decreasing relative PFD, indicating both factors to be important in determining the distribution of N area. Due to the effect of leaf position on N area, leaves of subordinate plants had a higher N area than older leaves of dominant plants which were at the same height or slightly higher in the canopy. Consequently, the N area distribution patterns of individual plants plotted as a function of relative PFD were steeper, and probably closer to the optimal distribution which maximizes photosynthesis, than the average distribution in the stand. Leaves of subordinate plants had a lower mass per unit area (LMA) than those of dominant plants. In the dominant plants, LMA decreased with decreasing relative PFD (and with leaf position) while in the subordinate plants it increased. This surprising result for the subordinate plants can be explained by the fact that, during the course of a growing season, these plants became increasingly shaded and newer leaves were thus formed at progressively lower light availability. This indicates that LMA was strongly determined by the relative PFD at leaf formation and to a lesser extent by the current PFD. Leaf N content per unit mass (N mass) was strongly determined by leaf position independent of relative PFD. This indicates that N mass is strongly ontogenetically related to the leaf-aging process while changes in N area, in response to PFD, were regulated through changes in LMA.

Effects of photon flux density on photosynthesis, growth, flowering, and oil content in Boronia

Boronia heterophylla is cultivated for cut flowers and B. megastigma for volatile oil production. Both species are endemic to south-western Western Australia and their natural habitat is often shaded by a canopy of Melaleuca parviflora or Eucalyptus marginata. Shade tents were used to examine the influence of reduced photon flux density (PFD) on photosynthesis, growth, and flower production in B. heterophylla and B. megastigma. Volatile oil content was also examined in B. megastigma. Photosynthesis in field-grown B. heterophylla was saturated at 16·2 µmol CO2/m 2·s under a PFD of 1022 µmol/m 2·s (75% full sunlight). Flower number was highest under 75% full sunlight but the number of harvestable stems was the same under 75% and full sunlight. More flowers were produced by B. megastigma plants grown under 75% full sunlight. Content of α-pinene and limonene decreased with decreasing light intensity, whereas β-ionone and docecyl acetate increased with decreasing light intensity

Effects of photon flux density on carbon partitioning and rhizosphere carbon flow of Lolium perenne

Effects of photon flux density on carbon partitioning and rhizosphere carbon flow of Lolium perenne

Effects of light photon flux density and spectral quality on photosynthesis and respiration in Porphyra yezoensis (Bangiales, Rhodophyta)

SUMMARYA comparative study on the effects of photon flux density and spectral quality on photosynthesis and respiration in the marine red alga Porphyra yezoensis Ueda was conducted using a light dispenser. Results showed that the photosynthetic response, expressed in light utilization efficiency (LUE) for preselected wave bands of photosynthetically active radiation, could be ranked as follows: white > green > red > blue. Differences in LUE were also found between conchocelis and gametophyte stages and different strains of the alga. Pre‐illumination light compensation, post‐illumination light compensation, light saturation, respiration and photorespiration were also measured and compared. The relationships between light exposure, photosynthetic capacity, and the natural environmental conditions are discussed.

Effects of photon flux density on carbon partitioning and rhizosphere carbon flow ofLolium perenne

The distribution and partitioning of dry matter and photoassimilate of Lolium perenne was investigated under two light regimes providing photosynthetically active radiation of 350 /imo m 2 s~1 (low light treatment) or 1000 //mol m 2 s~1 (high light treatment). Plants were grown at specific growth conditions in either soil or sand microcosm units to follow the subsequent release of carbon into the rhizosphere and its consequent incorporation into the microbial biomass (soil system) or recovery as exudates (sand system). The distribution of recent assimilate between the plant and root released carbon pools was determined using 14C02 pulse-chase methodology at both light treatments and for both sand- and soil-grown seedlings. A significant (P<0.05) increase in partitioning of Relabel below-ground occurred for both soil- and sandgrown seedlings at the increased light treatment. Incorporation of recent assimilate into the microbial biomass, however, was unaltered by light treatment. Total plant biomass of L. perenne seedlings grown in the sand microcosm unit was unaffected by light treatment, but differences in partitioning of biomass did occur resulting in an increased root-to-shoot ratio under high light. Soil-grown L. perenne seedlings showed a large (81%) and significant (P< 0.001) increase in shoot biomass under high light with a consequent decrease in root-to-shoot ratio. Specific leaf area was altered in the soil grown plants only, where it decreased under high light. Total organic carbon (TOC) content of the recovered exudate material was measured throughout the 14 d experimental period and during the 14C-chase period. Comparison of plant C budgets using these two measurements is discussed.

Nitrogen allocation in response to partial shading of a plant: Possible mechanisms

The significance of photosynthetic and transpiration rates for the perception by plants of light gradients in leaf canopies has been investigated with regard to nitrogen allocation and re‐allocation. A gradient of photon flux density (PFD) over a plant's foliage was simulated by shading one leaf of a pair of primary leaves of bean (Phaseolus vulgaris L. cv. Rentegever). Photosynthetic rate was manipulated independently of PFD and, to some extent, also of transpiration, by subjecting the leaf to different CO2 concentrations. Transpiration rate was changed independently of PFD and photosynthetic rate by subjecting the leaf to different vapour pressure differences (VPD). A reduced partial pressure of CO2 reduced specific leaf mass (SLM) as did a decreased PFD, but did not change leaf N per unit area (NLA) and light saturated rate of photosynthesis (Amax). A reduced VPD caused several effects consistent with the effect of PFD. It decreased NLA and Amax and increased the chlorophyll to N ratio in old and young leaves. Furthermore, it decreased the chlorophyll a to b ratio and inhibited leaf growth in young leaves. The transpiration stream is partitioned among the leaves of a plant according to their transpiration rates. The results suggest that relative rates of import of xylem sap into leaves of a plant play an important role in the perception of partial shading of a plant, a situation normally found in dense vegetations. The possible role of cytokinin influx into leaves as controlled by transpiration rate, is discussed.