Fluence-response curves

Fig. 11. Fluence response curves of photophorogenesis. Mycelia, 50 h after inoculation, were irradiated for 1 min at the indicated intensities. Filled circles = wt NRRL1555 open circles C173 (car B32 car R21). From Galland and Russo (1979 in press)...

Takahashi This was work in Mike Menaker s lab in 1984. We did full fluence response curves at three wavelengths 400, 500 and 600 nm. The slopes of those three curves were the same. The principle of univariance held for that data set. I think there is a species difference. Many years later we did another species of hamster and we found the same thing as Russell Foster. We never published this. 

Fig.21. Comparison of dose response curves (top) and fluence-response curves bottom). Both panels are based on the same data fluences are converted to doses according to Eq. (3)...

Derivation of Action Spectrum from Fluence-Response Curves. 112-5... 

When an action spectrum is derived from fluence-response curves, the condition of reciprocity should be valid over the range of fluence rates and exposure times used. In other words, the response should depend on the product of fluence rate and exposure time but should not otherwise depend on either factor. 

To derive an equal-response action spectrum from fluence-response curves, the first step is to specify a criterion response level. Then, for each wavelength, the fluence (or fluence rate) needed to produce that standard response should be determined. Choices for the criterion response include the following ... 

The absolute threshold fluence rate (often extrapolated downward to the baseline from the Unearly rising part of the fluence-response curve note that an alternative approach that should be avoided would be to try to find the limiting fluence at which there just begins to be a perceptible response the difficulty is that this measure is highly susceptible to experimental noise and subjective judgment see below for a further discussion of threshold measurements)... 

It is assumed implicitly that the fluence response curves are monotonic, or at least that the corresponding criterion response points on the curves are chosen (otherwise, if the fluence-response curve were, for example, bell-shaped, there would be two values of fluence with the same response value, and one could conceivably err by choosing noncorresponding points on curves for different wavelengths). From Equation 2, it is evident that the cross section at any wavelength X is inversely proportional to the applied fluence that produces the criterion response at that wavelength, or <=. ... 

In the semilogarithmic plot (Figure 112.1a), the curves have the same sigmoidal shape and differ only by lateral displacement. The symmetrical sigmoidal shape is a property of the hyperbolic saturation function, which is frequently used to fit fluence-response curves and other types of stimulus-response relationships in sensory physiology, - in photochemical kinetics, and in other areas of biophysics and biology, including the well-known MichaeHs-Menten enzyme kinetics (see below). 

TABLE 112.1 Representative Functions for Fluence-Response Curve Fits... 

Given in Table 112.1 are several functional forms that are useful for fitting fluence-response curves. These are all based on the hyperbolic saturation function given above and shown in the top row of the... 

Beyond the key recommendation of basing action spectra on fluence-response curves, readers are encouraged to apply formal data analysis techniques, including error analysis, for analyzing experimental results in action spectroscopy research. Details on such methods are available elsewhere. ... 

Corrochano, L.M. et al.. Photomorphogenesis in Phycomyces fluence-response curves and action spectra, Planta, 174, 315,1988. 

Trad, C.H. and Lipson, E.D., Biphasic fluence-response curves and derived action spectra for light-induced absorbance changes in Phycomyces mycelium, /. Photochem. Photobiol B Biol, 1,169,1987. 

Pulse-Induced Phototropism Fluence-Response Curves Pulse-Induced Phototropism Dependence on Adaptation Pulse-Induced Phototropism Effect of Red Light, Phytochrome Continuous Irradiation Fluence-Rate-Response Curves Continuous Irradiation ... 

Pulse-Induced Phototropism Fluence-Response Curves... 

FIGURE 132.1 Photon fluence-response curves for phototropic bending of Avena coleoptiles. (A) Coleoptiles were irradiated unilaterally with a blue-light pulse (458 nm) of constant duration (30 s) and variable photon-fluence rates. (B) Irradiation with constant photon-fluence rates (0.01,0.1, and 1 pmol s ) and variable pulse duration. Bending angles were measured 2 h after the unilateral light pulse. 

Numerous phototropic organisms display fluence-response relationships that are similar to those of grass coleoptiles. These include various monocots and dicots, Phycomyces, Pilobolus, Arabidopsis, Vauche-ria, and chloronemata of the fern Dryopteris. " ° The fluence-response curves for the phototropism of Raphanus seedlings appear less typical in that a classical bell-shaped curve for the first positive phototropism is absent. Kinetic models for the complex dose-response relationships were proposed by several authors. ... 

A preirradiation with a strong pulse of blue light desensitizes transiently Avena coleoptiles and causes a shift of the entire bell-shaped fluence-response curve for fPlPP. In Zea coleoptiles, preirradiation reduces mainly the phototropic responsivity, not however, the absolute threshold. After about 120 min in darkness, the responsivity recovers, and the original bell-shaped curve for the fPIPP is reestablished, indicating that the full sensitivity has recovered. "- Earlier authors who worked with a sequence of strong conditioning pulses and subsequent unilateral pulses of lesser irradiance similarly found evidence for... 

A pretreatment of dark-grown Avena or Zea coleoptiles with red light exerts a dual effect on fPiPP it raises the threshold of fluence-response curves in fact, the entire curve with the ascending and descending arms of the fPIPP is shifted to elevated fluences, and it slightly increases the maximal bending angle - . 

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