B Alternative Sinks for Reducing Equivalents

Photosynthesis includes processes other than photorespiration and C02 fixation. Nitrate and nitrite reduction, sulfate reduction, and amino acid, lipid and other biosynthetic activities are all important light driven metabolic processes (ap Rees, 1987 Robinson, 1988 Bloom et al., 1989 Brunold, 1993 Hanning and Heldt, 1993). In fact, it appears that in developing leaves photosynthetic activity is predominantly coupled to processes other than C02 fixation and photorespiration (Baker, 1985). The...

Proposed Mechanisms for q E Quenching

Xanthophyll Cycle

There is wide agreement that the principal role of qE is dissipation of excited state energy in competition with photochemistry, fluorescence and other decay processes as a means of regulating the utilization of absorbed light energy and minimizing damage from excess light absorption. Because the yields of stable energy storage in the reaction center and fluorescence emission from the antenna both decrease with increasing qE, it is assumed that qE arises from anew process which ultimately...

The Need for More Specific Measurements

Further quantitative characterization of what happens inside the black box will demand new fluorescence techniques, or the combination of fluorescence measurements with other techniques Brugnoli and Bjorkman, 1992 Bilger and Bjorkman, 1994 . The same generalization can be made for those other approaches which we may loosely term 'general indicators of photosynthetic flux or status.' These include steady-state photoacoustic measurements, C02 uptake, photothermal radiometry, and delayed...