Dynamics of chlorophyll fluorescence parameters under drought condition for three desert shrub species

  Objective  Research on the response process of physiological parameters of desert plants to natural environment fluctuations can better understand and predict the impact of climate change on desert ecosystems.

  Method   We conducted in situ field measurements of chlorophyll fluorescence for three desert shrub species (Artemisia ordosica, Salix psammophila and Hedysarum mongolicum) to explore the responses of photosystem II (PSII) maximum quantum yield (F_v / F_m), photochemical efficiency (Φ_PSII) and non-photochemical quenching (NPQ) to environmental factors, in order to understand the PSII photosynthetic physiology and its photoprotection mechanism of desert shrubs in arid environment.

  Result  Under water stress (soil water content < 0.08 m³/m³), F_v / F_m and Φ _PSII of three kinds of desert shrubs were reduced and NPQ increased (P < 0.01). The F_v / F_m of S. psammophila was lower than that of A. ordosica and higher than H. mongolicum (P < 0.01). The Φ_PSII of H. mongolicum was lower than both A. ordosica and S. psammophila (P < 0.01). The Φ_PSII and NPQ for three typical desert shrubs presented a clear daily variation with photosynthetic active radiation (PAR), and also were affected by air temperature (T_a), relative humidity (RH) and vapor pressure difference (VPD). Three shrub species resisted drought stress through heat dissipation mechanism, but had different degrees. The F_v / F_m of A. ordosica can be restored to an appropriate value of about 0.75 through self-regulation of heat dissipation, and its reaction center damage was recoverable. H. mongolicum was greatly affected by drought stress, and its photoprotective response of heat dissipation was sensitive.

  Conclusion  A. ordosica can be considered as the first choice for vegetation restoration in arid areas, S. psammophila is the second and H. mongolicum is not recommended. The activity of PSII reaction center is characterized by changes in chlorophyll fluorescence parameters, which can fully reflect the response strategy of desert shrubs to environmental fluctuations, and can be used as an important means to explore the response of desert plants in arid and semi-arid areas to environmental changes.