Photo-reducible plastoquinone pools in chloroplasts of Tradescentia plants acclimated to high and low light.

In photosynthetic systems of oxygenic type, plastoquinone (PQ) molecules are reduced by photosystem II (PSII). The turnover of PQ determines the rate of PSII operation. PQ molecules are present in surplus with respect to PSII. In this work, using the pulse amplitude modulation-fluorometry technique, we quantified photo-reducible PQ pools in chloroplasts of two contrasting ecotypes of Tradescantia, acclimated either to low light (~ 100 μmol photons·m ·s , LL) or to high light (~ 1000 μmol photons·m ·s , HL). The LL-grown plants are characterized by higher capacity of rapidly reducible PQ pool ([PQ] /[PSII] ≈ 8) as compared to HL-grown plants of both species ([PQ] /[PSII] ≈ 4). The elevated content of PQ in LL plants favours photosynthetic electron flow at low-solar irradiance.