Hydrogen sulphide alleviates oxidative damage and enhances light energy transformation under high light for Dendrobium officinale

• Natural light intensity overran 500 μmol m−2 s−1 will induce the photoinhibition for Dendrobium officinale.
• Hydrogen sulfide increases activities of antioxidant enzymes.
• Hydrogen sulfide maintained higher level of photochemical quenching parametes.
• Hydrogen sulfide alleviated the photoinhibition and preserved the PSII from the photodamage.

Hydrogen sulphide (H2S) is an important biological messenger in plants, which has been implicated in response to abiotic stress. To study the effects of H2S on plant under high light menace, the seedlings of Dendrobium officinale were selected and treated with high light (800 μmol m−2 s−1) to simulate photoinhibition. After application of sodium hydrogen sulphide (NaHS), the antioxidant enzyme activities and chlorophyll fluorescence parameters were determined. The results showed that the plant supplied with 200 μmol L−1 NaHS maintained higher activities of antioxidant enzymes and lower content of malondialdehyde (MDA) during high light treatment. However, higher concentration of NaHS (600 μmol L−1) enhanced the effects of high light stress for plant. For further analysis of the response mechanism against to high light, the chlorophyll fluorescence parameters were determined. As a result, when the seedlings were treated with 200 μmol L−1 NaHS, levels of chlorophyll parameters: Fv/Fm, ФPSII, ФNPQ, qP, qL, NPQ and ETR were obviously increased. The parameter ФNO was maintained lower. 200 μmol L−1 NaHS treatment alleviated the photoinhibition and preserved the PSII from the photodamage. Contrarily, 600 μmol L−1 NaHS treatment enhanced the photoinhibition and photodamage to PSII. Thus, the protection effect on plant under high light stress depends on the concentrations of H2S. These results may imply that 200 μmol L−1 NaHS treatment triggered increase of antioxidant enzyme activities, which may be the reason that H2S could protect PSII against oxidative damage caused by high light.