Enhancement of the Photosynthesis of Chlorella pyrenoidosa as a Function of Far-Red and Short-Wave Illuminations

Abstract

Enhancement of photosynthesis of C. pyrenoidosa in far-red (696m[mu]) and short-wave (482m[mu]) illuminations was studied. Both E (the ratio of the rate of photosynthesis supported by far-red in the presence of short-waves to the rate supported by far-red in the absence of short-waves) and D (the excess photosynthesis rate generated in enhancement) were characterized as functions of far-red and short-wave illuminations. By reference to respiratory and saturated photosynthetic rates, the functions E and D were related to the illumination curve of photosynthesis. The magnitude of D, which reached values as high as 0.04 of saturated rate, and the fact that D increased with illumination up to illuminations giving approximately 30% of saturated rate, demonstrated clearly that enhancement is photosynthetic and not due to light-induced respiratory inhibitions. Analytical formulations of the "spill-over" and "separate package" hypotheses of enhancement were devised. The essential characteristics of the observed dependences of E and D on illumination are in accord with both the spill-over and separate package hypotheses, with the provisos that (1) the distribution of short-wave quanta between the 2 photoreactions is a continuous function of illumination, and (2) light saturation of photosynthesis is taken into account.