Gerber D W, Burris J E
Department of Biology, The Pennsylvania State University, University Park, Pennsylvania 16802.
Plant Physiol. 1981 Sep;68(3):699-702. doi: 10.1104/pp.68.3.699.
The marine diatom Amphora sp. was grown at a light intensity of 7.0 x 10(15) quanta centimeter(-2) second(-1). Light saturation of photosynthesis for these cells was between 6.0 and 7.0 x 10(16) quanta centimeter(-2) second(-1). At light intensities greater than saturation, photosynthetic (14)CO(2) fixation was depressed, while P700 unit size (chlorophyll a concentration/P700 activity) increased and number of P700 units per cell decreased. After a 1-hour exposure of Amphora sp. to a photoinhibitory light intensity of 2.45 x 10(17) quanta centimeter(-2) second(-1), there was a 45 to 50% decrease in the rate of (14)CO(2) fixation relative to the rate at the culture light intensity. There also was a 25% increase in P700 unit size and a 30% reduction in the number of P700 units per cell but no change in total chlorophyll a concentration. Following this period of photoinhibition, the cells were returned to a light regime similar to that in the original culture conditions. Within 1 hour, both number of P700 units per cell and P700 unit size returned to levels similar to those of cells which were kept at the culture light intensity. The rates of photosynthesis did not recover as rapidly, requiring 2 to 3 hours to return to the rate for the nonphotoinhibited cells. Our results indicate that a decrease in P700 activity (with a resultant increase in P700 unit size) may be partially responsible for the photoinhibition of algal photosynthetic carbon dioxide fixation.
海洋硅藻双眉藻属（Amphora sp.）在光强为7.0×10¹⁵ 量子·厘米⁻²·秒⁻¹ 的条件下培养。这些细胞光合作用的光饱和点在6.0至7.0×10¹⁶ 量子·厘米⁻²·秒⁻¹ 之间。在光强高于饱和点时，光合¹⁴CO₂固定受到抑制，而P700单位大小（叶绿素a浓度/P700活性）增加，每个细胞中P700单位的数量减少。将双眉藻属暴露于2.45×10¹⁷ 量子·厘米⁻²·秒⁻¹ 的光抑制光强1小时后，相对于培养光强下的速率，¹⁴CO₂固定速率下降了45%至50%。P700单位大小也增加了25%，每个细胞中P700单位的数量减少了30%，但叶绿素a总浓度没有变化。在这段光抑制期之后，细胞被放回与原始培养条件相似的光照条件下。1小时内，每个细胞中P700单位的数量和P700单位大小都恢复到了与保持在培养光强下的细胞相似的水平。光合作用速率恢复得没有那么快，需要2至3小时才能恢复到未受光抑制细胞的速率。我们的结果表明，P700活性的降低（导致P700单位大小增加）可能部分导致了藻类光合二氧化碳固定的光抑制。
