Figure 2.

Typical spectral and kinetic changes that occur upon rapid shuttering of actinic light. Changes in absorbance, estimated by (−ΔI/I₀)/2.3, were obtained in an intact tobacco, with the use of a diffused optics flash spectrophotometer at a series of wavelengths as described in the text. The background actinic light was set at 900 μmol photons⋅m⁻²⋅s⁻¹ and shuttered for approximately 40 ms every 15 s. Data were averaged over eight traces at each wavelength. Measurements were made at 1.4, 3.4, 5.4, 7.4, 8.4, 10.4, 12.4, 15.4, and 25.4 ms after half-shutter closure for curves represented by open squares, closed squares, open circles, closed circles, open triangles, closed triangles, open diamonds, closed diamonds, and open hexagons, respectively. (Inset) Dark interval relaxation kinetics at 520 nm under the same conditions. The shutter was half-closed at time 0. The full extent of the 520-nm change was 0.0215 ΔI/I₀ units.