PHOTOTACTIC ACTION SPECTRUM FOR WHITEFLY AND THE QUESTION OF COLOUR VISION

1972 ◽  
Vol 104 (3) ◽  
pp. 299-307 ◽  
Author(s):  
Fergus D. H. Macdowall
Keyword(s):  
Absorption Spectrum ◽  
Light Intensity ◽  
Transmission Spectrum ◽  
Colour Vision ◽  
Monochromatic Light ◽  
Action Spectrum ◽  
Light Traps ◽  
Phototactic Response ◽  
Colorimetric Data

AbstractThe peak of phototactic response of Trialeurodes (Asterochitori) vaporariorum (Westw.) to equal numbers of quanta of monochromatic light in the range 475–625 mμ occurred at 540–550 mμ. and a hump of "red" sensitivity occurred near 600 mμ. This coincided with the transmission spectrum of host leaves. The response to light intensity was hyperbolic but it was linear within the variance in the range used for the action spectrum. Corrections were made for decreasing sensitivity during experiments. The absorption spectrum of a pigmented eye-preparation included a shoulder at the wavelength that caused maximal phototaxy. Work on greenhouse light traps is recommended. Preliminary colorimetric data did not support a capacity for colour vision.

scholarly journals Bacteriorhodopsin induces a light-scattering change in Halobacterium halobium.

1978 ◽  
Vol 79 (3) ◽  
pp. 657-662 ◽  
Author(s):  
C L Wey ◽  
P L Ahl ◽  
R A Cone
Keyword(s):  
Absorption Spectrum ◽  
Light Scattering ◽  
Near Infrared ◽  
Action Spectrum ◽  
Bright Light ◽  
Infrared Region ◽  
Halobacterium Halobium ◽  
Scattering Response ◽  
Near Infrared Region ◽  
Hypertonic Shock

When suspensions of Halobacterium halobium are exposed to bright light, the light-scattering properties of the bacteria change. This light-scattering response can produce a transmission decrease of about 1% throughout the red and near-infrared region. The action spectrum for the light-scattering response appropriately matches the absorption spectrum of bacteriorhodopsin. The response is eliminated by cyanide p-trifluoro-methoxyphenylhydrazone, a proton ionophore, and by triphenylmethylphosphonium, a membrane permanent cation. A mild hypertonic shock induces a similar light-scattering change, suggesting that bright light causes the bacteria to shrink about 1% in volume, thereby producing the light-scattering response.

scholarly journals Spectral Tuning of White Light Allows for Strong Reduction in Melatonin Suppression without Changing Illumination Level or Color Temperature

2018 ◽  
Vol 33 (4) ◽  
pp. 420-431 ◽  
Author(s):  
Jan L. Souman ◽  
Tobias Borra ◽  
Iris de Goijer ◽  
Luc J. M. Schlangen ◽  
Björn N. S. Vlaskamp ◽  
...  
Keyword(s):  
White Light ◽  
High Power ◽  
Spectral Power ◽  
Monochromatic Light ◽  
Action Spectrum ◽  
Color Temperature ◽  
Light Spectrum ◽  
Melatonin Suppression ◽  
Dim Light ◽  
Melatonin Production

Studies with monochromatic light stimuli have shown that the action spectrum for melatonin suppression exhibits its highest sensitivity at short wavelengths, around 460 to 480 nm. Other studies have demonstrated that filtering out the short wavelengths from white light reduces melatonin suppression. However, this filtering of short wavelengths was generally confounded with reduced light intensity and/or changes in color temperature. Moreover, it changed the appearance from white light to yellow/orange, rendering it unusable for many practical applications. Here, we show that selectively tuning a polychromatic white light spectrum, compensating for the reduction in spectral power between 450 and 500 nm by enhancing power at even shorter wavelengths, can produce greatly different effects on melatonin production, without changes in illuminance or color temperature. On different evenings, 15 participants were exposed to 3 h of white light with either low or high power between 450 and 500 nm, and the effects on salivary melatonin levels and alertness were compared with those during a dim light baseline. Exposure to the spectrum with low power between 450 and 500 nm, but high power at even shorter wavelengths, did not suppress melatonin compared with dim light, despite a large difference in illuminance (175 vs. <5 lux). In contrast, exposure to the spectrum with high power between 450 and 500 nm (also 175 lux) resulted in almost 50% melatonin suppression. For alertness, no significant differences between the 3 conditions were observed. These results open up new opportunities for lighting applications that allow for the use of electrical lighting without disturbance of melatonin production.

Photorespiration and the postillumination CO2 burst

1971 ◽  
Vol 49 (8) ◽  
pp. 1277-1284 ◽  
Author(s):  
N. R. Bulley ◽  
E. B. Tregunna
Keyword(s):  
Light Intensity ◽  
Action Spectrum ◽  
Visible Spectrum ◽  
Sample Volume ◽  
Gas Analysis ◽  
Short Period ◽  
Rate Of Photosynthesis ◽  
Measurable Rate ◽  
Soybean Leaves ◽  
Sudden Reduction

An open system of gas analysis was used to study the kinetics of the short postillumination CO2 burst (PIB) from soybean leaves. After correcting for the sample volume in the gas analyzer (IRGA), we found that the maximum measurable rate of CO2 evolution occurred within 8 s after the sudden reduction in light intensity, lasted for about 6 s, and then declined rapidly. The corrected rate was 45% higher than the rate indicated by the IRGA output. The maximum rate of the PIB was proportional to the effect of light intensity on the preceding apparent rate of photosynthesis in 21% O2 and 350 ppm CO2. A similar proportionality was found between the PIB and the light intensity in each of the five parts of the visible spectrum which were tested. No PIB was found when the O2 concentration was reduced to less than 2% O2. The effect of 21% O2 on the rate of CO2 evolution after 8 s in the dark relative to the rate in 2% O2 was about 20% greater than the effect of 21% O2 on apparent photosynthesis in the preceding light period. This difference may be ascribed to internal refixation during photosynthesis.The results supported the theory that photorespiration continues for a short period longer than photosynthesis after a sudden reduction in light intensity. This period is much shorter than previous papers have indicated. The action spectrum for the PIB provides no support for flavin-activation as the mechanism of the light effect.

scholarly journals Modification of Cyclic Nucleotide–Gated Ion Channels by Ultraviolet Light

2000 ◽  
Vol 116 (2) ◽  
pp. 227-252 ◽  
Author(s):  
Thomas R. Middendorf ◽  
Richard W. Aldrich ◽  
Denis A. Baylor
Keyword(s):  
Absorption Spectrum ◽  
Ion Channels ◽  
Ultraviolet Light ◽  
Cyclic Nucleotide ◽  
Uv Light ◽  
Action Spectrum ◽  
Light Sensitivity ◽  
Current Reduction ◽  
Photochemical Modification ◽  
Gated Ion Channels

We irradiated cyclic nucleotide–gated ion channels in situ with ultraviolet light to probe the role of aromatic residues in ion channel function. UV light reduced the current through excised membrane patches from Xenopus oocytes expressing the α subunit of bovine retinal cyclic nucleotide–gated channels irreversibly, a result consistent with permanent covalent modification of channel amino acids by UV light. The magnitude of the current reduction depended only on the total photon dose delivered to the patches, and not on the intensity of the exciting light, indicating that the functionally important photochemical modification(s) occurred from an excited state reached by a one-photon absorption process. The wavelength dependence of the channels' UV light sensitivity (the action spectrum) was quantitatively consistent with the absorption spectrum of tryptophan, with a small component at long wavelengths, possibly due to cystine absorption. This spectral analysis suggests that UV light reduced the currents at most wavelengths studied by modifying one or more “target” tryptophans in the channels. Comparison of the channels' action spectrum to the absorption spectrum of tryptophan in various solvents suggests that the UV light targets are in a water-like chemical environment. Experiments on mutant channels indicated that the UV light sensitivity of wild-type channels was not conferred exclusively by any one of the 10 tryptophan residues in a subunit. The similarity in the dose dependences of channel current reduction and tryptophan photolysis in solution suggests that photochemical modification of a small number of tryptophan targets in the channels is sufficient to decrease the currents.

Spectral sensitivity of the electroretinogram b-wave in dark-adapted goldfish

1988 ◽  
Vol 1 (2) ◽  
pp. 159-168 ◽  
Author(s):  
Jonathan D. Nussdorf ◽  
Maureen K. Powers
Keyword(s):  
Absorption Spectrum ◽  
Spectral Sensitivity ◽  
Neural Activity ◽  
Dark Adaptation ◽  
Carassius Auratus ◽  
Action Spectrum ◽  
Absolute Threshold ◽  
Selective Loss

AbstractThe action spectrum of the ERG b-wave was measured under dark-adapted conditions in intact goldfish (Carassius auratus). It is substantially broader than the absorption spectrum of goldfish rod porphyropsin. Neither prolonged dark adaptation nor removal of possible efferent neural activity affected its shape. Moreover, a 682-nm background did not produce a selective loss of sensitivity to long wavelengths. The results imply that the spectral sensitivity of the b-wave in dark-adapted goldfish reflects the influence of at least two photoreceptor types which act as a single univariant mechanism near absolute threshold.

The host-finding behaviour of the hen flea, Ceratophyllus gallinae (Schrank) (Siphonaptera)

Parasitology ◽  
1968 ◽  
Vol 58 (2) ◽  
pp. 403-414 ◽  
Author(s):  
David A. Humphries
Keyword(s):  
Light Intensity ◽  
Water Loss ◽  
Main Part ◽  
Host Finding ◽  
Critical Discussion ◽  
Avian Host ◽  
Tactile Stimuli ◽  
Phototactic Response ◽  
Secondary Distribution ◽  
Ceratophyllus Gallinae

Field and laboratory observations on the nature and sequence of the host-finding responses of the hen flea Ceratophyllus gallinae are described. The imago over-winters within the cocoon. Tactile stimuli and a rise in temperature initiate emergence. Emigration from the nest is delayed for a few days by a negatively phototactic response, and begins when this becomes positive. The fleas are negatively geotactic and disperse upwards into the vegetation. Eventually they take up a characteristic posture, oriented towards the light. Jumping is elicited when the light intensity is suddenly reduced, and it is suggested that this enables the fleas to reach their avian host. Those fleas whose jump misses the host fall and form a secondary distribution on the ground. The readiness to jump rises during the first few days after cocoon emergence, then falls again, the rate of fall apparently being partly determined by water loss.The author is much indebted to the Hon. Miriam Rothschild and Drs E. T. Burtt and M. J. Cotton for valuable advice, and to C. R. Brannigan for a critical discussion of the manuscript. The main part of the research was carried out during tenure of a post-graduate studentship provided by the Department of Scientific and Industrial Research.

scholarly journals AKTIVITAS TERMOPROTEKSI DAN FOTOPROTEKSI EKSTRAK KASAR KAROTENOID MESOKARP KELAPA SAWIT (Elaeis guineensis Jacq.) TERHADAP KESTABILAN KLOROFIL-A)

2019 ◽  
Vol 12 (1) ◽  
pp. 112-123
Author(s):  
Dece Elisabeth Sahertian ◽  
Indriatmoko Indriatmoko ◽  
Leenawaty Limantara ◽  
Tatas Hardo Panintingjati Brotosudarmo
Keyword(s):  
Absorption Spectrum ◽  
Light Intensity ◽  
Chlorophyll A ◽  
Elaeis Guineensis ◽  
Heating Time ◽  
Protective Function ◽  
Stability And Instability ◽  
In Series ◽  
Elaeis Guineensis Jacq ◽  
The Stability

AbstrakKelapa sawit (Elaeis guineensis Jacq.) merupakan tanaman yang mengandung karotenoid tinggi pada mesokarp yang merupakan bagian dari buah. Cahaya dan suhu dalam proses fotosintesis memberi pengaruh bagi kestabilan dan ketidakstabilan karotenoid dan klorofil. Penelitian ini bertujuan untuk mengetahui aktivitas fotostabilitas dan termostabilitas ekstrak karotenoid mesokarp terhadap klorofil-a yang diiradiasi dengan lampu volpi (intralux 4100) daylight pada intensitas cahaya 31960 lux, 47040 lux dan 76640 lux dalam seri waktu penyinaran 0, 5, 10, 15, 20, 25, dan 30 menit serta dipanaskan pada suhu 25, 50, 65, dan 90 °C dengan seri waktu pemanasan 0, 1, 2, 3, 6, 9, dan 24 jam. Pengukuran spektrum serapan tiap perlakuan diukur menggunakan Spektrofotometer UV-Tampak pada panjang gelombang 300–800 nm. Hasil penelitian menunjukkan bahwa karotenoid tidak melakukan fungsi proteksi dengan baik pada perlakuan pemanasan 65 °C dan 90 °C selama 24 jam, serta perlakuan iradiasi hingga 30 menit pada ketiga intensitas cahaya. Kesimpulan dari penelitian ini adalah klorofil-a murni lebih stabil pada perlakuan pemanasan dan iradiasi. Kemampuan proteksi karotenoid terhadap kestabilan klorofil-a yaitu pada suhu di bawah 50 °C dan pada intensitas cahaya di bawah 31960 lux.Abstract Oil palm (Elaeis guineensis Jacq.) is a plant that contains high carotenoids in its mesocarp which is part of the fruit. Light and temperature in photosynthesis may affect the stability and instability of carotenoid and chlorophyll. The aim of this research was to examine the thermostability and photostability activities of the carotenoids in mesocarp extract on chlorophyll which were irradiated by Volpi lamp (4100 intralux) daylight at light intensity of 31960 lux, 47040 lux and 76640 lux in series of time radiation 0, 5, 10, 15, 20, 25, and 30 minutes and heated at 25, 50, 65, and 90°C with series of heating time 0, 1, 2, 3, 6, 9, and 24 hours. Measurement of the absorption spectrum of each treatment was measured using a UV-Vis Spectrophotometer at a wavelength range of 300–800 nm. The results showed the protective function of carotenoids did not perform well at the heating treatments of 65°C and 90°C in 24 hours and at the irradiation for 30 minutes in all the light intensities. In conclusion, pure chlorophyll-a is more stable in heating and irradiation treatments. Carotenoid protection ability against chlorophyll-a is at temperatures below 50 °C and at a light intensity below 31960 lux.

Inactivation of Tissue Thromboplastin by Ultraviolet Irradiation

1968 ◽  
Vol 19 (01/02) ◽  
pp. 221-225
Author(s):  
S Åtland ◽  
M Hvatum ◽  
H Prydz
Keyword(s):  
Absorption Spectrum ◽  
Exponential Function ◽  
Ultraviolet Irradiation ◽  
Uv Light ◽  
Action Spectrum ◽  
Radiation Energy ◽  
Procoagulant Activity ◽  
Tissue Thromboplastin ◽  
Protein Part ◽  
Uv Absorption Spectrum

SummarySolutions of partially purified tissue thromboplastin have been irradiated with UV light of different wavelengths, and the resulting reduction in the procoagulant activity has been measured. The activity decreased as an exponential function of the dose. The action spectrum obtained was closely similar to the UV absorption spectrum of the thromboplastic preparations and had a maximum between 270-290 nm. The data suggested that the reduction in the procoagulant activity was caused by absorption of radiation energy in the protein part of the thromboplastic structure.

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