Diminished photoinhibition is involved in high photosynthetic capacities in spring ephemeral Berteroa incana under strong light conditions

Berteroa incana (B. incana), a spring ephemeral species of Brassicaceae, possesses very high photosynthetic capacities at high irradiances. Exploring the mechanism of the high light use efficiency of B. incana under strong light conditions may help to explore mechanisms of plants' survival strategies. Therefore, the photosynthetic characteristics of B. incana grown under three different light intensities (field conditions (field): 200-1500μmolphotonsm(-2)s(-1); greenhouse high light (HL) conditons: 600μmolphotonsm(-2)s(-1); and greenhouse low light (LL) conditions: 100μmolphotonsm(-2)s(-1)) were investigated and compared with those of the model plant Arabidopsis thaliana (A. thaliana). Our results revealed that B. incana behaved differently in adjusting its photosynthetic activities under both HL and LL conditions compared with what A. thaliana did under the same conditions, suggesting that the potential of photosynthetic capacity of B. incana might be enhanced under strong light conditions. Under LL conditions, B. incana reached its maximum photosynthetic activity at a much higher light intensity than A. thaliana did, although their maximum photochemical efficiency of photosystem II (PSII) (F(v)/F(m)) was almost the same. When grown under HL conditions, B. incana showed much higher photosynthetic capacity than A. thaliana. A detailed analysis of the OJIP transient kinetics of B. incana under HL and LL conditions revealed that HL-grown B. incana possessed not only a high ability in regulating photosystem stoichiometry that ensured high linear electron transport, but also an enhanced availability of oxidized plastoquinone (PQ) pool which reduced non-photochemical quenching (NPQ), especially its slow components qT and qI, and increased the photochemical efficiency, which in turn, increased the electron transport. We suggest that the high ability in regulating photosystem stoichiometry and the high level of the availability of oxidized PQ pool in B. incana under strong light conditions play important roles in its ability to retain higher photosynthetic capacity under extreme environmental conditions.