Temporal dynamics in photosynthetic electron transfer rate of Artemisia ordosica in growing season and its response to environmental factors in Mu Us Sandy Land of northwestern China

  Objective  Understanding the dynamics of electron transfer rate of typical sandy speices Artemisia ordosica and its response mechanism to environmental factors in desert area is very important to manage desert ecosystem to adapt to the fluctuating environment.

  Method  This study conducted a long-term in situ continuous monitoring of photosynthetic electron transfer rate (ETR) in Artemisia ordosica in May−September of 2019 using chlorophyll fluorescence observation method. Photosynthetically active radiation (PAR), air temperature (T_a), chlorophyll content (SPAD) were simultaneously measured.

  Result  ETR was significantly correlated with PAR, T_a and SPAD at a significant level of 0.05, with the monthly average reaching the maximum in July and the smallest in September. The change of ETR with light intensity showed an upward trend, and the response intensity to light under low light condition of PAR ≤ 800 μmol/(m²·s) was greater than that of strong light. The change of ETR with T_a showed a trend of first increasing and then decreasing. The thresholds of high and low temperature stress in May (leaf-leaning stage) and September (deciduous stage) were 5 ℃ and 20 ℃, respectively, and June−August (mature stage) was 10 ℃ and 25 ℃. The relationship between ETR and SPAD was linear and positive, and the stability of ETR in mature stage was less than that in leaf-expansion stage and leaf-falling stage.

  Conclusion  Through the above research, it was found that PAR, T_a, and SPAD were the three main factors affecting ETR. ETR was mainly affected by SPAD during the leaf-expansion stage, temperature and light intensity during the mature stage, and plant physiology during the defoliation stage. We found that Artemisia ordosica ETR showed a good adaptability under the alternating effect of the main influencing factors. Besides proper temperature increase can promote the transfer of photosynthetic electrons, thus enhance the photosynthetic capacity of plants. The results can not only provide some theoretical guidance for the response of plants’ photosynthetic physiology to the environment under global warming, but also a reference for the restoration of desert vegetation.