a1_Shallow ponds with rapidly photosynthesising cyanobacteria or eukaryotic algae are used for growing biotechnology feedstock and have been proposed for biofuel production but a credible model to predict the productivity of a column of phytoplankton in such ponds is lacking. Oxygen electrodes and Pulse Amplitude Modulation (PAM) fluorometer technology were used to measure gross photosynthesis (PG) vs. irradiance (E) curves (PG vs. E curves) in Chlorella (chlorophyta), Dunaliella salina (chlorophyta) and Phaeodactylum (bacillariophyta). PG vs. E curves were fitted to the waiting-in-line function [PG = (PGmax × E/Eopt) × exp(1 — E/Eopt)]. Attenuation of incident light with depth could then be used to model PG vs. E curves to describe PG vs. depth in pond cultures of uniformly distributed planktonic algae. Respiratory data (by
O2-electrode) allowed net photosynthesis (PN) of algal ponds to be modelled with depth. Photoinhibition of photosynthesis at the pond surface reduced PN of the water column. Calculated optimum depths for the algal ponds were: Phaeodactylum, 63 mm; Dunaliella, 71 mm and Chlorella, 87 mm. Irradiance at this depth is ≈ 5 to 10 μmol m-2 s-1 photosynthetic photon flux density (PPFD). This knowledge can then be used to optimise the pond depth. The total net P N [μmol(O2) m-2 s-1] were: Chlorella, ≈ 12.6 ± 0.76; Dunaliella, ≈ 6.5 ± 0.41; Phaeodactylum ≈ 6.1 ± 0.35. Snell’s and Fresnel’s laws were used to correct irradiance for reflection and refraction and thus estimate the time course of PN over the course of a day taking into account respiration during the day and at night. The optimum PN of a pond adjusted to be of optimal depth (0.1-0.5 m) should be approximately constant because increasing the cell density will proportionally reduce the optimum depth of the pond and vice versa., a2_Net photosynthesis for an optimised pond located at the tropic of Cancer would be [in t(C) ha-1 y-1]: Chlorella, ≈ 14.1 ± 0.66; Dunaliella, ≈ 5.48 ± 0.39; Phaeodactylum, ≈ 6.58 ± 0.42 but such calculations do not take weather, such as cloud cover, and temperature, into account., R. J. Ritchie, A. W. D. Larkum., and Obsahuje bibliografii a dodatky
Irradiance data software developed by the NREL Solar Radiation Laboratory (Simple Model of Atmospheric Radiative Transfer of Sunshine, SMARTS) has been used for modelling photosynthesis. Spectra and total irradiance were expressed in terms of quanta [mol m-2 s-1, photosynthetic photon flux density, PPFD (400-700 nm)]. Using the SMARTS software it is possible to (1) calculate the solar spectrum for a planar surface for any given solar elevation angle, allowing for the attenuating effects of the atmosphere on extraterrestrial irradiance at each wavelength in the 400-700 nm range and for the thickness of atmosphere the light must pass through during the course of a day, (2) calculate PPFD vs. solar time for any latitude and date and (3) estimate total daily irradiance for any latitude and date and hence calculate the total photon irradiance for a whole year or for a growing season. Models of photosynthetic activity vs. PPFD are discussed. Gross photosynthesis (Pg) vs. photosynthetic photon flux density (PPFD) (Pg vs. I) characteristics of single leaves compared to that of a canopy of leaves are different. It is shown that that the optimum irradiance for a leaf (Iopt) is the half-saturation irradiance for a battery of leaves in series. A C3 plant, with leaves having an optimum photosynthetic rate at 700 μmol m-2 s-1 PPFD, was used as a realistic worked example. The model gives good estimates of gross photosynthesis (Pg) for a given date and latitude. Seasonal and annual estimates of Pg can be made. Taking cloudiness into account, the model predicts maximum Pg rates of about 10 g(C) m-2 d-1, which is close to the maximum reported Pg experimental measurements. and R. J. Ritchie.
Chlorophyll fluorescence measurements showed that plasticity to salinity in stems of Salicornia ramosissima is expressed at a modular level, so intraplant variation should be considered in further studies. and S. Redondo-Gómez ... [et al.].
Current research on the effect of increased UV-B radiation on crop production has been limited to exposing plants to improbable UV-B dose or growth condition. The objective of this study was to test the effects of short-term modulated increased UV-B radiation on maize (Zea mays L.) growth, grain yield, and quality under field conditions for three years. A modulated irradiance system was used to maintain UV-B radiation at 30% above the ambient level and was applied daily between the elongation and silking stages of maize. The result indicated that increased UV-B radiation adversely affected maize growth and yield, especially on plant height when UV-B was enhanced at the elongation stage and on yield when UV-B was enhanced near the silking stage. Yield reduction that induced by enhanced UV-B radiation was associated with reductions in number of kernels per row and kernel mass. Protein content of grains was increased with enhanced UV-B radiation, but oil and starch contents were not affected. This study confirmed the sensitivity of maize to increased UV-B radiation under the field condition, and contributed to understand the full negative and positive effects of increased UV-B radiation on crop production., L. N. Yin, S. W. Wang., and Obsahuje bibliografii
We investigated the effect of moderate Cu2+ and Cd2+ stress by applying chlorophyll (Chl) fluorescence and P700 absorbance measurements to monitor the photosynthetic electron transport activity of 3-week-old Pisum sativum L. cv. Petit Provençal plants grown in a modified Hoagland solution containing 50 μM CuSO4 or 5 μM CdCl2. Both heavy metals caused a slight inhibition in PSII photochemistry as indicated by the decrease in the effective quantum efficiency of PSII (ΦPSII), the maximum electron transport capacity (ETRmax), and the maximum quantum yield for electron transport (α). PSI photochemistry was also affected by these heavy metals. Cu2+ and Cd2+ decreased the quantum efficiency of PSI (ΦPSI) as well as the number of electrons in the intersystem chain, and the Cu2+ treatment significantly reduced the number of electrons from stromal donors available for PSI. These results indicate that PSII and PSI photochemistry of pea plants are both sensitive to moderate Cu2+ and Cd2+ stress, which in turn is easily detected and monitored by Chl fluorescence and P700 absorbance measurements. Therefore, monitoring the photochemistry of pea plants with these noninvasive, yet sensitive techniques offers a promising strategy to study heavy metal toxicity in the environment., B. Wodala ... [et al.]., and Obsahuje bibliografii
Athyrium pachyphlebium C. is a popular ornamental fern with considerable shade tolerance. The aim of this study was to investigate how the mature sporophytes acclimate to different light levels and to obtain an optimal light environment for their growth both in natural forest canopy and in urban landscapes. Plant growth and morphology, photosynthetic light-response curves and chlorophyll (Chl) fluorescence were measured at four different light levels (45% full sunlight, 30%, 20% and 8%). As the light intensities declined from 45% to 20%, seedling height, crown growth, foliage number and plant lifespan increased significantly. Seedlings grown at 20% light level were vigorous with great ornamental value. Plants grown in deep shade (8% light) showed severe symptoms of lodging and in 45% full sun, the plants showed highlight-stress symptoms. Seedlings in high light levels exhibited a higher
light-saturated photosynthetic rate (P max), light compensation point (LCP), light saturation point (LSP) and a reduced ability for nonphotochemical quenching (NPQ) of excess light than those in low light levels. However, seedlings in low light exhibited greater efficiency in absorbing and utilizing light energy, characterized by higher chlorophyll b (Chl b) and electron transport rate (ETR). These results indicated that a light level of about 20% full sun appeared to be optimal for A. pachyphlebium when both physiological and morphological performance in the landscape were considered. and D. Huang ... [et al.].
This paper describes the technical information and performance of a new multi-objective chamber system enabling the control of environmental variables (e.g., temperature, CO2, air humidity, wind speed, and UV-B radiation) for understanding plant responses to climate change. Over a whole growing season, four different climate scenarios were evenly programmed into the system’s 16 chambers as ambient environment (AMB), elevated temperature (ET), elevated CO2 concentration (EC) and elevated temperature and CO2 concentration (ETC). Simultaneously, the chamber effects were assessed regarding the physiological responses and growth of a boreal perennial grass (reed canary grass, Phalaris arundinacea L.). During the growing season, the chamber system provided a wide variety of climatic conditions for air temperature (T a), relative humidity (RH) and CO2 concentration (C a) in the AMB chambers following outside conditions. The target temperature (+3.5°C) was achieved to a good degree in the ET and ETC chambers, being on average 3.3°C and 3.7°C higher than ambient conditions, respectively. The target concentration of CO2 (700 ppm) was also well achieved in the EC and ETC chambers, being on average 704 ppm and 703 ppm, respectively. The stable airflow condition inside all of the chambers provided a homogeneous distribution of gases and temperature. The decreases in RH and increases in vapour pressure deficit (VPD) in the elevated temperature chambers were also maintained at a low level. Chamber effects were observed, with some physiological and growth parameters of plants being significantly lower in the AMB chambers, compared to outside conditions. The plant growth was negatively affected by the reduced radiation inside the chambers., X. Zhou ... [et al.]., and Obsahuje bibliografii
Miscanthus is one of the most promising bioenergy crops with high photosynthetic nitrogen-use efficiency (PNUE). It is unclear how nitrogen (N) influences the photosynthesis in Miscanthus. Among three Miscanthus genotypes, the net photosynthetic rate (PN) under the different light intensity and CO2 concentration was measured at three levels of N: 0, 100, and 200 kg ha-1. The concentrations of chlorophyll, soluble protein, phosphoenolpyruvate carboxylase (PEPC), ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) large subunit, leaf anatomy and carbon isotope discrimination (Δ) in the leaf were analyzed to probe the response of photosynthesis in Miscanthus genotypes to N levels. PN in all genotypes rose significantly as N application increased. The initial slope of response curves of PN to Ci was promoted by N application in all genotypes. Both stomatal conductance and Ci were increased with increased N supply, indicating that stomatal factors played an important role in increasing PN. At a given Ci, PN in all genotypes was enhanced by N, implying that nonstomatal factors might also play an important role in increasing PN. Miscanthus markedly regulated N investment into PEPC rather than the Rubisco large subunit under higher N conditions. Bundle sheath leakiness of CO2 was constant at about 0.35 for all N levels. Therefore, N enhanced the photosynthesis of Miscanthus mainly by increasing stomatal conductance and PEPC concentration., X.-P. Feng ... [et al.]., and Obsahuje bibliografii
For Tunisian olive tree orchards, nitrogen deficiency is an important nutritional problem, in addition to the availability of water. Establishment of relationships between nutrients such as nitrogen and ecophysiological parameters is a promising method to manage fertilisation at orchard level. Therefore, a nitrogen stress experiment with one-year-old olive trees (Olea europaea L. 'Koroneiki' and 'Meski') was conducted with trees respectively subjected to four nitrogen supply regimes (23.96 meq l-1, 9.58 meq l-1, 4.79 meq l-1 and 0 meq l-1 NO3-).
The current paper focuses on the use of the SPAD-502 portable chlorophyll (Chl) meter, a nondestructive method for fertilisation management under nitrogen stress conditions of olive trees. Maximum net photosynthetic assimilation rates, chlorophyll fluorescence parameters and the SPAD Chl index were therefore measured simultaneously and the Chl and nitrogen content of the leaves were analysed. Significant correlations were established in the olive tree leaves between SPAD-502 readings on the one hand and Chl content, nitrogen content, photosynthetic assimilation rate, and Chl fluorescence parameters (ΦPSII and ETR) on the other hand. and O. Boussadia ... [et al.].