Short-term photoacclimation and photoregulation strategies of Sargassum horneri in response to temperature and light

Sargassum horneri (Turner) C. Agardh is a genus of brown algae and plays an important role in marine ecosystem. However, the inhabiting area of S. horneri has been decreasing sharply in China. To understand the photoacclimation and photoregulation strategies of S. horneri in responses to temperature and light, S. horneri was cultured under different temperatures [18℃ (LT) and 26℃ (HT)] and light intensities [60 μmol(photon) m-2 s-1 (LL) and 120 μmol(photon) m-2 s-1 (HL)] for 7 d, and then the chlorophyll a fluorescence parameters were measured. The results showed that the maximum electron transfer rate occurred at low temperature and high light (LT-HL) condition. The high temperature was the predominant factor for causing inhibition of PSII, lowering the effective quantum yield of PSII, and reducing the nonphotochemical quenching (NPQ). However, high light could improve the photoprotective ability via enhancing the NPQ. On the other hand, a strong linear relationship was observed between NPQ and the electron transport efficiency (α); the increase of NPQ could reduce the α value and avoid damage from high light stress to PSII. Therefore, S. horneri was found to be well adapted to grow under LT-HL conditions.