Fluence-rate-response curves

Wayne, R., Kadota, A, Watanabe, M., and Furuya, M., Photomovement in Dunaliella salina fluence rate-response curves and action spectra, Planta, 184, 515,1991. 

Also, the fluence rate-response curves in narrow-band monochromatic Hght follow the same hyperboHc saturation behavior, while the saturation level is the same for all wavelengths, within experimental errors. This indicates that if there is more than one type of photoreceptor pigment, they are functionally equivalent (same fluence rate-response curve, same saturation level). A simpler, and perhaps simpHstic, solution is that we are dealing with only one type of pigment. 

In etiolated WT tomato seedhngs, the fluence-rate response curve for anthocyanin accumulation with 24 h monochromatic red Hght shows that is possible to isolate two components a low fluence rate response (multiple LFR) and a fluence rate-dependent high irradiance response (HIR). > PhyA mutant shows only the R-HIR component and lacks the LFR response to red Hght. On the contrary,phyBl mutant lacks the R-HIR component. Etiolated phyA phyBl mutant lacks any detectable response. The absence... 

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 ... 

FIGURE 132.2 Photon-fluence rate-response curves for photogravitropic equilibrium. Sporangiophores of Phyco-myces unilateral irradiation for 8 h (465 nm) above 10 tmol m s irradiation for 6 h with broad-band blue light. Coleoptiles of Avena unilateral irradiation for 8 h (465 nm)." Coleoptiles of Oryza unilateral irradiation for 5 h with broad-band blue light."... 

Continuous Irradiation Fluence-Rate-Response Curves... 

Action spectra that were generated on the basis of fluence-rate-response curves (continuous irradiation for several hours) exist mostly for Phycomyces2 The fine structures of these action spectra differ from those of the balance action spectra in that the UVA peak is much higher. Everett and Thiman analyzed the so-called second positive phototropic response that is time dependent. AH of these action spectra have in common a steep drop of the effectiveness above 500 nm. 

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)... 

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. 

---