Effect Of Photon Flux Density Research Articles

The influence of photon flux density (PFD) on short term 14C incorporation into proteins, carbohydrates and lipids in freshwater algae

The effect of photon flux density (PFD) on the partitioning of photosynthetically fixed 14CO2-C into major intracellular end products was investigated for three species of freshwater planktonic algae (Nitzschia palea, Monoraphidium minutum and Synechococcus elongatus belonging to three different classes. This study was designed to investigate the phenomenon of polysaccharide synthesis associated with the saturation of protein synthesis and to test if this process is common to all three phytoplankton species. Protein synthesis was saturated at low PFD in all three species of algae studied. However, fixed carbon was differentially stored, namely in lipids in Nitzschia palea (Bacillariophyceae), in polysaccharides in Monoraphidium minutum (Chlorophyceae), and in low molecular weight metabolites (LMW) in Synechococcus elongatus (Cyanophyceae). The results of this transient state study indicate that the metabolic pathways of algae can easily be controlled by different irradiance. Furthermore, it appears that the difference in the patterns of synthesis is taxonomy dependent.

Effects of leaf age, nitrogen nutrition and photon flux density on the distribution of nitrogen among leaves of a vine (Ipomoea tricolor Cav.) grown horizontally to avoid mutual shading of leaves.

Effects of leaf age, nitrogen nutrition and photon flux density (PFD) on the distribution of nitrogen among leaves were investigated in a vine, Ipomoea tricolor Cav., which had been grown horizontally so as to avoid mutual shading of leaves. The nitrogen content was highest in newly developed young leaves and decreased with age of leaves in plants grown at low nitrate concentrations and with all leaves exposed to full sunlight. Thus, a distinct gradient of leaf nitrogen content was formed along the gradient of leaf age. However, no gradient of leaf nitrogen content was formed in plants grown at a high nitrate concentration. Effects of PFD on the distribution of nitrogen were examined by shading leaves in a manner that simulated changes in the light gradient of an erect herbaceous canopy (i.e., where old leaves were placed under increasingly darker conditions with growth of the canopy). This canopy-type shading steepened the gradient of leaf nitrogen content in plants grown at a low nitrogen supply, and created a gradient in plants grown at high concentrations of nitrate. The steeper the gradient of PFD, the larger the gradient of leaf nitrogen that was formed. When the gradient of shading was inverted, that is, younger leaves were subjected to increasingly heavier shade, while keeping the oldest leaves exposed to full sunlight, an inverted gradient of leaf nitrogen content was formed at high nitrate concentrations. The gradient of leaf nitrogen content generated either by advance of leaf age at low nitrogen availability, or by canopy-type shading, was comparable to those reported for the canopies of erect herbaceous plants. It is concluded that both leaf age and PFD have potential to cause the non-uniform distribution of leaf nitrogen. It is also shown that the contribution of leaf age increases with the decrease in nitrogen nutrition level.

Effect of Environmental Factors on Carbon Dioxide Exchange and Essential Oil Yield inOlearia phlogopappa(Labill.)

ABSTRACT The effect of day length, night temperatures and photon flux density on the growth and oil yield of the Tasmanian native species, Olearia phlogopappa (Labill.) were examined. High photon flux densities (PFD) resulted in significant increases in plant height, stem diameter and percentage oil yield. In addition, 16 h periods of photosynthetically active radiation increased plant height and percentage dry matter. Infrared gas analysis was used to study the effect of PFD and temperature on carbon dixoide assimilation. Light saturation occurred at 200 to 400 μmol.m−2S−1. Adaptation to low temperatures is evident in that optimum photosynthesis occurs at 15–20°C, but is greater at 5°C than at temperatures above 25°C. First-year leaves have higher rates of assimilation than second-year leaves. This is in agreement with the observation that more essential oil is accumulated in first-year leaves than in second-year leaves.

Effects of photon flux density, CO2, aeration rate, and inoculum density on growth and extracellular polysaccharide production byPorphyridium cruentum

Growth and extracellular polysaccharide production byPorphyridium cruentum were measured as a function of several culture parameters. Photon flux density of 75 μmol m−2 s−1 and CO2 concentration of 2.5% were found to be optimum for both growth and extracellular polysaccharide production. Interactive studies on these two parameters further confirmed that at these levels of photon flux density and CO2, when applied together, both growth (5.9·107 cells per mL) and extracellular polysaccharide production (1.9 g/L) were at the maximum. Maximum growth and extracellular polysaccharide production were observed at inoculum density of 106 cells per mL and aeration rate of 500 mL air per min per liter.

The effect of photon flux density on distribution of assimilate between shoot and storage root of carrot, red beet and radish

Growth and 14C distribution were measured in carrot, red beet and radish exposed to different photosynthetic photon flux densities (PPFD) in controlled environments to permit a comparison with their responses to varying plant density. Growth studies revealed that red beet maintains its leaf area, shoot fresh and dry weights at a range of PPFD while its storage organ weight is markedly reduced as PPFD decreases. Experiments with 14C showed that the beet shoot apex was a strong sink for assimilates and mobilised 14C at the expense of the storage root. In carrot, leaf area and shoot fresh weight were also maintained across a range of PPFD, though shoot and storage root dry matter were reduced at lower PPFD. The distribution of 14C suggested that in carrot there was a tendency to mobilise 14C to the apex at the expense of the leaf lamina at lower PPFD. In radish, leaf area and the fresh and dry weights of both shoot and storage organ decreased as PPFD decreased, but with the storage organ affected to a greater extent. The tendency in red beet and radish to mobilise assimilate to the shoot at the expense of the storage organs at lower PPFD (in contrast to carrot) is consistent with the response of these species to increasing density.

Effect of photon flux density on carbon assimilation and chlorophyll a fluorescence of cold-stored white spruce and lodgepole pine seedlings.

White spruce (Picea glauca (Moench.) Voss) and lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings previously held in dark, frozen storage (-2 degrees C) for 2.5 or 6 months, and nursery-grown white spruce seedlings lifted in summer were exposed to photon flux densities (PFDs) similar to those that might be encountered at planting. Photosynthetic gas exchange and chlorophyll a (chl a) fluorescence were examined in cold-stored and summer-lifted seedlings before and after a 9 h-exposure to artificial illumination of high PFD (2000 micro mol m(-2) s(-1)) or low PFD (ca. 500 micro mol m(-2) s(-1)), and during exposure to 400 micro mol m(-2) s(-1) for 4-9 days. In the 2.5-month-stored and summer-lifted seedlings, the high-PFD treatment caused a small decrease in carbon fixation and a large decrease in the ratio of variable to maximum fluorescence (F(v)/F(m)) relative to the effect of the low-PFD treatment. In contrast, in the 6-month-stored seedlings the high-PFD treatment caused a significant decrease in rate of light-saturated carbon fixation but little decrease in F(v)/F(m) relative to the effect of the low-PFD treatment, indicating that the mechanisms for maintaining integrity of the photochemical apparatus had changed during the storage interval.

Effects of physical factors on the survival and growth of antarctic terrestrial algae

The survival and growth of four genera of cyanobacteria and microalgae isolated from Antarctic fellfield soils were investigated. Survival of freezing and desiccation were studied by vital staining, and the effects of photon flux density (PFD) and temperature on growth rates were determined by direct counts of cultures maintained on a thermogradient bar. Monitoring of seasonal changes in environmental factors in a fellfield ecosystem demonstrated that the experiments were carried out under ecologically relevant conditions. The coccoid chlorophyte Planktosphaerella exhibited the highest growth rates under most conditions. Growth rates of the other species were similar to each other, although the diatom Pinnularia maintained near-maximum growth rates over a wider range of conditions than the filamentous cyanobacterium Phormidium or the filamentous chlorophyte Zygnema. Maximum growth of all species occurred at 15–20°C and no growth was observed at 0°C, indicating that there is little adaptation to growth at low temperature. Optimal PFD was generally 100–400 μmol m-2 s-1 and photoinhibition of growth occurred at a PFD significantly lower than that incident on the soil surface, even on cloudy days. Such results are consistent with the observation that the soil flora largely occurs beneath the surface of the soil where PFD is reduced. All species survived repeated 24 h freeze-thaw cycles, following an initial decline on the first cycle. Survival of desiccation differed markedly between species, from a few hours in Planktosphaerella to many weeks in Phormidium and Pinnularia, and is probably a major factor in the ability of these genera to colonize the fellfield soils.

Effect of photon flux density on bud dormancy release in Norway spruce seedlings.

Effect of photon flux density on bud dormancy release in Norway spruce seedlings.

PIGMENT AND PHOTOSYNTHETIC RESPONSES OF OSCILLATORIA AGARDHII (CYANOPHYTA) TO PHOTON FLUX DENSITY AND SPECTRAL QUALITY1

ABSTRACTThe effects of photon flux density (PFD) and spectral quality on biomass, pigment content and composition, and the photosynthetic activity of Oscillatoria agardhii Gomont were investigated in steady‐state populations. For alterations of PFD, chemostat populations were exposed to 50, 130 and 230 μmol photons·m−2·s−1 of photosynthetic active radiation (PAR). Decreases in biomass, chlorophyll a (Chl a) and c‐phycocyanin (CPC) contents, and CPC: Chl a and CPC: carotenoid content was not altered. Increases in the relative abundances of myxoxanthophyll and zeaxanthin and deceases in the relative abundances of echinenone and β‐carotene within the carotenoid pigments coincided with increasing PFD. Increases in Chl a‐specific photosynthetic rates and maxima and decreases in biomass‐specific photosynthetic rates and maxima with increasing PFD were attributed to increased light harvesting by carotenoids per unit Chl a and reduction in total pigment content, respectively.Responses to spectral quality were tested by exposing chemostat populations to a gradient of spectral transmissions at 50 μmol photons·m−2·s−1 PAR. Biomass differences among populations were likely attributable to the distinct absorption of the PAR spectrum by Chl a, CPC, and carotenoids. Although pigment contents were not altered by spectral quality, relative abundances of zeaxanthin and echinenone in the carotenoid pigments increased in populations exposed to high‐wavelength PAR. The population adapted to green light possessed a greater photosynthetic maximum than populations adapted to other spectral qualities.

Effect of photon flux density on inorganic carbon accumulation and net CO2 exchange in a high-CO2-requiring mutant of Chlamydomonas reinhardtii

The effect of photon flux density on inorganic carbon accumulation and photosynthetic CO2 assimilation was determined by CO2 exchange studies at three, limiting CO2 concentrations with a ca-1 mutant of Chlamydomonas reinhardiii. This mutant accumulates a large internal inorganic carbon pool in the light which apparently is unavailable for photosynthetic assimilation. Although steady-state photosynthetic CO2 assimilation did not respond to the varying photon flux densities because of CO2 limitation, components of inorganic-carbon accumulation were not clearly light saturated even at 1100 μmol photons m(-2) s(-1), indicating a substantial energy requirement for inorganic carbon transport and accumulation. Steady-state photosynthetic CO2 assimilation responded to external CO2 concentrations but not to changing internal inorganic carbon concentrations, confirming that diffusion of CO2 into the cells supplies most of the CO2 for photosynthetic assimilation and that the internal inorganic carbon pool is essentially unavailable for photosynthetic assimilation. The estimated concentration of the internal inorganic carbon pool was found to be relatively insensitive to the external CO2 concentration over the small range tested, as would be expected if the concentration of this pool is limited by the internal to external inorganic carbon gradient. An attempt to use this CO2 exchange method to determine whether inorganic carbon accumulation and photosynthetic CO2 assimilation compete for energy at low photon flux densities proved inconclusive.

The Effect of Photon Flux Density and Duration of the Photosynthetic Period on Growth and Dry Matter Distribution in Carrot

The distribution of dry matter between shoot and storage root of carrot plants grown in light regimes varying in intensity, duration and integral, is used to test an hypothesis for the control of assimilate partition Results from seven varieties show that shoot to storage root weight ratios are affected by the light environment, but that these effects are associated with the effect of light on plant size It is concluded that quantitative alterations to the supply of assimilate, resulting from variation in the light regime, do not affect its partition to different organs This is discussed in relation to other investigations which have suggested a relationship between the duration of the photosynthetic period, assimilate sequestration in foliar starch and partition between shoot and root

The effects of shading on the establishment and growth of Acacia tortilis seedlings

Examination of Acacia tortilis seedling germination and establishment relative to canopy cover of trees showed a greater proportion of newly germinated seeds per unit area, but a lower proportion of established seedlings, under canopies when compared with open (i.e. between canopy) areas. To examine the potential role of shading on seedling distribution in the field, the effects of photon flux density (PFD) on the growth rate and biomass allocation of Acacia tortilis seedlings were examined. Seedlings were grown for a period of 6 weeks under controlled environmental conditions at PFD’s of 770,430,330, and 150 μ mol m − 2 s − 1 . There was a significant decrease in biomass production (root and shoot, root length and leaf area) with decreasing PFD. Height growth was stimulated by reduced light levels resulting in an inverse relationship between the ratio of plant height/shoot weight and PFD. The ratio of root/shoot declined, whereas both leaf area ratio (leaf area/total weight) and root biomass/leaf area increased with decreasing PFD. Relative growth rate (whole plant) was initially lower for seedlings grown under the lowest light treatments. However, with time, higher leaf area ratio offset lower net assimilation rate for the two lowest light treatments, eliminating differences in relative growth rate among treatments. The ecological implications of reduced production and changes in carbon allocation under reduced light levels in semi-arid savannas are discussed.

Effects of light, salinity and nutrient limitation on the production of β-1,3- d-glucan and exo- d-glucanase activity in Skeletonema costatum (Grev.) Cleve

Dilution cultures of the marine diatom Skeletonema costatum (Grev.) Cleve were used to study the effect of photon flux density (PFD), salinity and nutrient limitation on the accumulation of the reserve polysaccharide β-1,3- d-glucan and β-1,3- d-glucanase activity. Generally, both the glucan content and the glucanase activity increased markedly with decreasing growth rates (increasing nutrient deficiency). The lowest PFD in this work (20 μE·m −2·s −1) was below saturation for growth while the highest (800 μE·m −2·s −1) was slightly inhibitory. The glucan accounted for between 7 and 80% of the total carbon content of the cells. The highest percentage was found in cells grown under strong nutrient limitation and subsaturating light conditions. The highest PFD led to a marked decrease in both glucan content and glucanase activity, while the lowest PFD had the opposite effect. At the lowest salinity tested (9%.), Skeletonema showed a marked decrease in growth rate while a salinity of 15%. gave no significant effect on growth rate. The glucanase activity as a main feature increased with decreasing salinity. Nutrient- limited cells containing large amounts of reserve material (β-1,3- d-glucan) assimilated nitrate when incubated in the dark. This assimilation led to a pronounced reduction in the glucan content of the cells.

Photosynthesis and transpiration by young Larix kaempferi trees: C3 responses to light and temperature

The effects of photon flux density and temperature on net photosynthesis and transpiration rates of mature and immature leaves of three‐year‐old Japanese larch Larix kaempferi (Lamb.) Sarg. trees were determined with an infrared, differential open gas analysis system. Net photosynthetic response to increasing photon flux densities was similar for different foliage positions and stage of maturity. Light compensation was between 25 and 50 μmol m−2 s−1. Rates of photosynthesis increased rapidly at photon flux densities above the compensation level and became saturated between 800 and 1000 μmol m−2 s−1. Transpiration rates at constant temperature likewise increased with increasing photon flux density, and leveled off between 800 and 1000 μmol m−2 s−1. Photosynthetic response to temperature was determined in saturating light and was similar for all foliage positions; it increased steadily from low temperatures to an optimum range betweeen 15 and 21°C and then decreased rapidly above 21°C. Transpiration rate, however, increased continuously with rising temperature up to the experimental maximum. CO2 compensation concentrations for mature foliage varied between 58 and 59 μl l−1; however, foliage borne at the apex of the terminal leader compensated at 75 μl l−1. None of these data support the claim that Japanese larch possesses C4 photosynthetic characteristics.

CO2 compensation concentration in bean Leaves: Effect of photon flux density and leaf age

Carbon dioxide compensation concentration,Г, net photosynthetic rate,Pn, and photorespiration rate,Rl, were measured in young, adult and old primary leaves ofPhaseolus vulgaris L. over a range of photon flux densities using a closed system with IRGA. Irrespective of leaf age,Г decreased rapidly with rising photon flux density up toca. 260 (μmol m−2 s−1. From this valueГ did not change with photon flux density under constant temperature, reaching on the average 178, 118 and 239 mg m−3 in young, adult and old leaves, respectively. Changes with age in curves relatingPn andRl to photon flux density were found.