Photosynthetic adaptation of Sargassum horneri in response to strong light stress
In recent years,the golden tide of drifting Sargassum horneri occurs frequently.As a specific bio-invasive phenomenon,it has huge negative impacts on marine ecosystems.When the golden tide outbreaks,the algae floating on the surface of seawater will receive higher solar radiation,but the photosynthetic response of this species to strong light stress remains unclear.In this study,the photosynthetic response and adaptive response of Sargassum horneri to strong light stress at three light levels(low light of 460 μmol/(m2·s),medium light of 920 μmol/(m2·s)and high light of 1 380 μmol/(m2·s))were investigated.The results showed that the photosynthetic efficiency of Sargassum horneri significantly reduced after strong light treatments for 120 min,and the maximum photochemical quantum yield(Fv/Fm)gradually decreased with the increasing of light intensity and exposure duration.In addition,the absorption energy,dissipated energy and energy captured for plastoquinone A reduction per reaction center significantly increased after strong light treatments.It also showed that the maximum relative electron transfer rate(Rmax)reduced by 28.83％,40.34％and 54.14％respectively at low,medium and high light levels compared with the initial rate.Meanwhile,algae exhibited resistance to light stress by increasing the net shutdown rate of PS Ⅱ reaction center,enhancing non-photochemical quenching and increasing carotenoid content.After recovering the weak light for 240 min,the Fv/Fm,Rmax and pigment contents of Sargassum horneri under three light treatments recovered to different degrees,and the Fv/Fm as well as the contents of chlorophyll a,chlorophyll c and carotenoid were restored to their initial values in the low light treatment.These results indicated that the photosynthesis of Sargassum horneri was stressed under different levels of strong light,and the alga could mitigate this stress by various photoprotective strategies,thus speculating that after strong light stress at midday,Sargassum horneri may largely recover by the weak light in the afternoon and evening,which allows them to adapt to the drifting life and causes outbreak of golden tide when other conditions are suitable.The results provide data support for revealing the physiological and ecological mechanism of Sargassum horneri golden tide formation.
万方数据
维普
