scholarly journals Fitomonitorizarea intensităţii fotosintezei, respiraţiei şi transpiraţiei la pomii de păr

2021 ◽  
Author(s):  
Gheorghe Siscanu ◽  
◽  
Gheorghe Scurtu ◽  
Nina Titova ◽  
◽  
...  
Keyword(s):  
Light Intensity ◽  
Synthesis Process ◽  
Saturation Curve ◽  
Light Saturation ◽  
Minimum Value ◽  
Physiological Processes ◽  
Total Light ◽  
Pear Trees ◽  
Func Tion

The paper presents the results regarding the phytomonitoring of physiological processes in pear trees. The modern RTM-48A phytomonitor was used, which allowed the measurement of indices in the form of a film-phytodiagram that allows the diagnosis of the properties of genotype and physiological con-dition of plants. The light saturation curve for photosynthesis in pear plants was determined as a result of the evaluation of the intensity of photosynthesis, respiration, transpiration, stomata conductivity as a func-tion of temperature, humidity and CO2 content in the air. The minimum value of light at which the photo-synthesis process is initiated has been established. As the light intensity increases (1/3 of the total light) the intensity of photosynthesis increases after the essential optimization of the process has taken place.

The Tetrazolium Reaction as a Measure of the Action of Diquat in Elodea

Weed Science ◽  
1968 ◽  
Vol 16 (3) ◽  
pp. 329-331 ◽  
Author(s):  
P. J. Davies ◽  
D. E. Seaman
Keyword(s):  
Light Intensity ◽  
Living Cells ◽  
Elodea Canadensis ◽  
Triphenyl Tetrazolium Chloride ◽  
Light Saturation ◽  
Tetrazolium Chloride ◽  
Light Intensities ◽  
Triphenyl Formazan

The production of red triphenyl formazan (hereinafter referred to as TPF) from colorless 2,3,5-triphenyl tetrazolium chloride (hereinafter referred to as TTC) by living cells was used as a vitality indicator for examining the effects of 6,7-dihydrodipyrido[1,2-a:2′,1′-c] pyrazidiinium salt (diquat) in elodea (Elodea canadensisMichx) shoots at varying light intensities. Diquat at 10 ppmw completely killed the elodea in 6 hr at 183 ft-c and at almost the same rate at 13,000 ft-c due to light saturation near the lower level. Over 24 hr were required for this effect in the dark. Between 29 and 183 ft-c, TPF production varied inversely with the light intensity. A comparison is made with the destruction of chlorophyll by diquat.

scholarly journals THE ORIENTATION OF ANIMALS BY OPPOSED BEAMS OF LIGHT

1927 ◽  
Vol 8 (6) ◽  
pp. 671-684 ◽  
Author(s):  
W. J. Crozier
Keyword(s):  
Experimental Data ◽  
Light Intensity ◽  
Total Light ◽  
Two Sides ◽  
Average Angle

When orientation is attained under the influence of beams of parallel light opposed at 180° the deflection θ from a path at right angles to the beams is given by tan See PDF for Equation, where I1 and I2 are the photic intensities and H is the average angle between the photoreceptive surfaces. This expression is independent of the units in which I is measured, and holds whether the primary photosensory effect is proportional to I or to log I. When photokinetic side-to-side motions of the head occur, H decreases with increasing total acting light intensity, but increases if higher total light intensity restricts the amplitude of random movements; in each case, H is very nearly proportional to log I1I2. For beams of light at 90°, See PDF for Equation. The application of these equations to some particular instances is discussed, and it is shown why certain simpler empirical formulæ previously found by others yield fair concordance with the experimental data. The result is thus in complete accord with the tropism theory, since the equations are based simply on the assumption that when orientation is attained photic excitation is the same on the two sides.

scholarly journals The ICAD (Iterative Cavity Enhanced DOAS) Method

2019 ◽  
Author(s):  
Martin Horbanski ◽  
Denis Pöhler ◽  
Johannes Lampel ◽  
Ulrich Platt
Keyword(s):  
Light Intensity ◽  
Gas Absorption ◽  
Optical Absorption Spectroscopy ◽  
Light Path ◽  
Calibration Source ◽  
Optical Cavities ◽  
Total Light ◽  
Averaging Time ◽  
Chemiluminescence Detector

Abstract. Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS or BB-CEAS DOAS) allows to make in-situ measurements while maintaining the km-long light paths required by DOAS. These technique have been successfully used for several years to measure in-situ atmospheric trace gases. A property of optical cavities is that in presence of strong absorbers or scatterers the light path is reduced, opposite to classical Long Path DOAS measurements. Typical CE-DOAS or BB-CEAS evaluation schemes correct this effect using the measured total light intensity attenuation. This makes them sensitive to any variations of the light intensity not arising from the trace gas absorption. That means an important DOAS advantage, to be independent of total light intensity, is actually lost. In order to cope with this problem, the instrument setup would require a thorough stabilisation of the light source and a very rigid mechanical setup, which would make instrumentation more complex and error prone. We present a new approach to Cavity Enhanced (CE-) DOAS based on an iterative algorithm (ICAD) which actually models the light path reduction from the derived absorbers in the optical resonator. It allows a sensitive and robust data analysis that does not depend on the total light intensity allowing a simpler and more compact instrument setup. The algorithm is discussed and simulated measurements demonstrate its sensitivity and robustness. Furthermore, a new NO2 ICAD instrument is presented. It takes advantage of the advanced data evaluation to build a compact (50 cm cavity) and light weight instrument (<10 kg) with low power consumption (25 W) for sensitive measurements of NO2 with a detection limit of 0.02 ppbv at an averaging time of 7 minutes. The instrument is characterized with a NO2 calibration source and good long term stability is demonstrated in a comparison with a commercial chemiluminescence detector. As a new application of ICAD we show measurements on an auto mobile platform to investigate the two dimensional NO2 distribution in an urban area. The instrument is so robust that even strong vibrations do not lead to any measurement problems.

Light Saturation of Growth and Photosynthesis of the Shade Plant Marchantia Polymorpha

1973 ◽  
Vol 12 (2) ◽  
pp. 391-401
Author(s):  
R. MACHE ◽  
S. LOISEAUX
Keyword(s):  
Growth Rate ◽  
Photosystem Ii ◽  
Light Intensity ◽  
Marchantia Polymorpha ◽  
Hill Reaction ◽  
Light Saturation ◽  
Shade Plant ◽  
Low Illumination ◽  
The Hill ◽  
Isolated Chloroplasts

The growth rate of the shade plant Marchantia was at its maximum for a low illumination, 2-3 x 103 lx, and was inhibited by an excess of light. Photosynthesis by intact thalli and by isolated chloroplasts of Marchantia was saturated by a light intensity of 2-3 x 103 lx. These isolated chloroplasts were able to carry on satisfactory rates of photosynthesis, up to 35 µM CO2/h/mg chlorophyll. The Hill reaction and photosystem II were also saturated by the same light intensities, demonstrating that the factor limiting the light saturation of photosynthesis is located in the chloroplast. The structure of chloroplasts was strongly modified by an excess of light, small grana and fret membranes being replaced by continuous grana.

scholarly journals Scattered Light in a Flood-plain Lake of Central Amazônia()

1972 ◽  
Vol 2 (2) ◽  
pp. 87-90
Author(s):  
W. L. B. Brinkmann
Keyword(s):  
Surface Layer ◽  
Light Intensity ◽  
Plant Communities ◽  
Water Surface ◽  
Scattered Light ◽  
Flood Plain ◽  
Near Surface ◽  
Central Amazonia ◽  
Total Light ◽  
Floating Plant

Abstract The light intensity below the surface of Lago Castanho was recorded at 10 minute intervals and compared to the total light intensity above the water surface. Scattered light of the lake water was rather constant and it was found to be sufficiently high to support the growth of photoautotrophic organisms in the near-surface layer. Below the floating plant communities scattered light was extremely low in intensity.

scholarly journals Effect of light on N<sub>2</sub> fixation and net nitrogen release of <i>Trichodesmium</i> in a field study

2018 ◽  
Vol 15 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Yangyang Lu ◽  
Zuozhu Wen ◽  
Dalin Shi ◽  
Mingming Chen ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Light Intensity ◽  
Carbon Fixation ◽  
Physiological State ◽  
Light Stress ◽  
Light Response ◽  
Light Change ◽  
Filamentous Cyanobacterium ◽  
Light Saturation ◽  
Net Release ◽  
Effect Of Light

Abstract. Dinitrogen fixation (NF) by marine cyanobacteria is an important pathway to replenish the oceanic bioavailable nitrogen inventory. Light is the key to modulating NF; however, field studies investigating the light response curve (NF-I curve) of NF rate and the effect of light on diazotroph-derived nitrogen (DDN) net release are relatively sparse in the literature, hampering prediction using models. A dissolution method was applied using uncontaminated 15N2 gas to examine how the light changes may influence the NF intensity and DDN net release in the oligotrophic ocean. Experiments were conducted at stations with diazotrophs dominated by filamentous cyanobacterium Trichodesmium spp. in the western Pacific and the South China Sea. The effect of light on carbon fixation (CF) was measured in parallel using the 13C tracer method specifically for a station characterized by Trichodesmium bloom. Both NF-I and CF-I curves showed a Ik (light saturation coefficient) range of 193 to 315 µE m−2 s−1, with light saturation at around 400 µE m−2 s−1. The proportion of DDN net release ranged from ∼ 6 to ∼ 50 %, suggesting an increasing trend as the light intensity decreased. At the Trichodesmium bloom station, we found that the CF ∕ NF ratio was light-dependent and the ratio started to increase as light was lower than the carbon compensation point of 200 µE m−2 s−1. Under low-light stress, Trichodesmium physiologically preferred to allocate more energy for CF to alleviate the intensive carbon consumption by respiration; thus, there is a metabolism tradeoff between CF and NF pathways. Results showed that short-term (< 24 h) light change modulates the physiological state, which subsequently determined the C ∕ N metabolism and DDN net release by Trichodesmium. Reallocation of energy associated with the variation in light intensity would be helpful for prediction of the global biogeochemical cycle of N by models involving Trichodesmium blooms.

The light saturation curve of photosynthesis

1970 ◽  
Vol 205 (2) ◽  
pp. 312-314 ◽  
Author(s):  
H.Arnold Herron ◽  
D. Mauzerall
Keyword(s):  
Saturation Curve ◽  
Light Saturation

Gas Exchange of Four Cassava Cultivars in Relation to Light Intensity

1982 ◽  
Vol 18 (4) ◽  
pp. 375-382 ◽  
Author(s):  
Jairo A. Palta
Keyword(s):  
Gas Exchange ◽  
Light Intensity ◽  
Flux Density ◽  
Direct Effect ◽  
Photosynthetic Rate ◽  
Photosynthetic Apparatus ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Saturation ◽  
Effect Of Light

SUMMARYGas exchange measurements were carried out on four cassava cultivars, M. COL22, M. MEX59, M. COL638, and M. VEN218, under a range of light intensities, to investigate possible differences in photosynthesis and transpiration. Over the range of photon flux density 100–1500 μE m−2 s−1 leaves showed a light saturation response typical of C-3 plants with little increase in photosynthetic rate above 1000–1500 μE m−2 s−1 (200–300 Wm−2 PAR). At light saturation there were significant differences in photosynthetic rates between cultivars, with the highest 10% greater than the lowest. Part of the response could be attributed to increased stomatal aperture, and a greater part to a direct effect of light intensity on the photosynthetic apparatus. Transpiration increased with light intensity levels, but no significant differences were observed between cultivars.

scholarly journals The ICAD (iterative cavity-enhanced DOAS) method

2019 ◽  
Vol 12 (6) ◽  
pp. 3365-3381 ◽  
Author(s):  
Martin Horbanski ◽  
Denis Pöhler ◽  
Johannes Lampel ◽  
Ulrich Platt
Keyword(s):  
Light Intensity ◽  
Gas Absorption ◽  
Optical Absorption Spectroscopy ◽  
Light Path ◽  
Calibration Source ◽  
Optical Cavities ◽  
Total Light ◽  
Averaging Time ◽  
Chemiluminescence Detector

Abstract. Cavity-enhanced differential optical absorption spectroscopy (CE-DOAS or BB-CEAS DOAS) allows us to make in situ measurements while maintaining the kilometre-long light paths required by DOAS. This technique has been successfully used for several years to measure in situ atmospheric trace gases. A property of optical cavities is that in the presence of strong absorbers or scatterers the light path is reduced, in contrast to classical long-path DOAS measurements where the light path is fixed. Typical CE-DOAS or BB-CEAS evaluation schemes correct this effect using the measured total light intensity attenuation. This makes them sensitive to any variations in the light intensity not arising from the trace gas absorption. That means an important DOAS advantage, to be independent of total light intensity, is actually lost. In order to cope with this problem, the instrument setup would require a thorough stabilisation of the light source and a very rigid mechanical setup, which would make instrumentation more complex and error prone. We present a new approach to cavity-enhanced (CE) DOAS based on an iterative algorithm (ICAD) which actually models the light path reduction from the derived absorbers in the optical resonator. It allows a sensitive and robust data analysis that does not depend on the total light intensity, allowing a simpler and more compact instrument setup. The algorithm is discussed and simulated measurements demonstrate its sensitivity and robustness. Furthermore, a new ICAD NO2 instrument is presented. It takes advantage of the advanced data evaluation to build a compact (50 cm cavity) and lightweight instrument (<10 kg) with low power consumption (25 W) for sensitive measurements of NO2 with a detection limit of 0.02 ppbv at an averaging time of 7 min. The instrument is characterised with a NO2 calibration source and good long-term stability is demonstrated in a comparison with a commercial chemiluminescence detector. As a new application of ICAD we show measurements on an automobile platform to investigate the two-dimensional NO2 distribution in an urban area. The instrument is so robust that even strong vibrations do not lead to any measurement problems.

CHYTRIDS AND ALGAE: II. FACTORS INFLUENCING PARASITISM OF RHIZOPHYDIUM SPHAEROCARPUM ON SPIROGYRA

1967 ◽  
Vol 45 (4) ◽  
pp. 431-440 ◽  
Author(s):  
D. J. S. Barr ◽  
C. J. Hickman
Keyword(s):  
Light Intensity ◽  
Pure Culture ◽  
Optimum Temperature ◽  
Light Saturation ◽  
Light Intensities ◽  
Alkaline Side ◽  
Culture Growth ◽  
Ph Range ◽  
Host Parasite ◽  
Effect Of Light

Host–parasite interrelationship studies showed that temperature was the most important environmental factor associated with epidemics of Rhizophydium sphaerocarpum (Zopf) Fischer on Spirogyra. Certain highly susceptible spring species of Spirogyra grew poorly or not at all at 30 C, the optimum temperature for R. sphaerocarpum, while resistant summer species grew well at 30 C, and even at 35 C. Both pure-culture growth of R. sphaerocarpum and infection of Spirogyra were optimal at approximately pH 7.0–7.5, falling off markedly below pH 6.0 and above pH 8.5. Spirogyra itself grew over a wider pH range, especially on the alkaline side. Infection of Spirogyra was negligible in darkness but a light intensity of 40 ft-c permitted some infection. No difference in infection occurred over a range of light intensities from 65 to 980 ft-c or in day lengths varying from 8 to 16 hours at a light intensity of 600 ft-c. Light saturation for Spirogyra was 400 ft-c. In contrast to the effect of light upon infection, pure culture growth of R. sphaerocarpum was considerably greater in total darkness than at light intensities of 20 ft-c or higher.

Sign in / Sign up

Export Citation Format

Share Document