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1272. Modelling photosynthesis in shallow algal production ponds

Creator:
Ritchie, R. J. and Larkum, A. W. D.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
botanika, botany, algal production ponds, Chlorella, Dunaliella, electron transport rate, light saturation curves, Phaeodactylum, photoinhibition, photosynthesis, photosynthesis vs. depth, primary productivity, pulse amplitude modulation fluorometry, 2, and 58
Language:
Multiple languages
Description:
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
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1278. Modulated increased UV-B radiation affects crop growth and grain yield and quality of maize in the field

Creator:
Yin, L. N. and Wang, S. W.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
botanika, botany, growth, maize, quality, UV-B radiation, yield, 2, and 58
Language:
Multiple languages
Description:
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
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1279. Modulation of substance P signaling by dipeptidyl peptidase-IV enzymatic activity in human glioma cell lines

Creator:
Petr Bušek, Jarmila Stremeňová, Evžen Křepela, and Aleksi Šedo
Format:
print, bez média, and svazek
Type:
article, články, model:article, and TEXT
Subject:
Biochemie. Molekulární biologie. Biofyzika, fyziologie, gliomy, vápník, physiology, gliomas, calcium, dipeptidyl peptidase, substance P, NK1 receptor, calcium signaling, 2, and 577
Language:
English
Description:
Dipeptidyl peptidase-IV (DPP-IV, CD26) is a serine protease almost ubiquitously expressed on cell surface and present in body fluids. DPP-IV has been suggested to proteolytically modify a number of biologically active peptides including substance P (SP) and the chemokine stro mal cell derived factor-1α (SDF-1α, CXCL12). SP and SDF-1α have been implicated in the regulation of multiple biological processes and also induce responses that may be relevant for glioma progression. Both SP and SDF-1α are signaling through cell surface receptors and use intracellular calcium as a second messenger. The effect of DPP-IV on intracellular calcium mobilization mediated by SP and SDF- α was monitored in suspension of wild type U373 and DPP-IV transfected U373DPPIV glioma cells using indicator FURA-2. Nanomolar concentrations of SP triggered a transient dose dependent increase in intracellular calcium rendering the cells refractory to repeated stimulation, while SDF-1α had no measurable effect. SP signaling in DPP-IV overexpressing U373DPPIV cells was not substantially different from that in wild type cells. However, preincubation of SP with the DPP-IV overexpressing cells lead to the loss of its signaling potential, which could be prevented with DPP-IV inhibitors. Taken together, DPP-IV may proteolytically inactivate local mediators involved in gliomagenesis., P. Bušek, J, Stremeňová, E. Křepela, A. Šedo., and Obsahuje bibliografii a bibliografické odkazy
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

1280. Mokřadní louky Sedlčanska - střípky z krajin minulých

Creator:
Jiří Malíček
Format:
print
Type:
article, články, model:article, and TEXT
Subject:
Botanika, flóra, mokřadní ekosystémy, louky, mokřady, Sedlčany (Česko), 2, and 58
Language:
Czech
Description:
In contrast to the typical Central Bohemian landscape, the Sedlčany region is characterized by quite a high concentration of wet meadows; most of them discovered during the last few years. Though it is only a fragment of their original extent. Suitable management is absent at most localities, but a restoration of farming on selected meadows has recently been started. and J.Malíček.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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