Leaf chlorophyll parameters and photosynthetic characteristic variations with stand age in a typical desert species (Haloxylon ammodendron)

Xiao-Hui He; Jian-Hua Si; Dong-Meng Zhou; Chun-Lin Wang; Chun-Yan Zhao; Bing Jia; Jie Qin; Xing-Lin Zhu

doi:10.3389/fpls.2022.967849

Leaf chlorophyll parameters and photosynthetic characteristic variations with stand age in a typical desert species (Haloxylon ammodendron)

Front Plant Sci. 2022 Oct 6:13:967849. doi: 10.3389/fpls.2022.967849. eCollection 2022.

Authors

Xiao-Hui He^{1

2

3}, Jian-Hua Si¹, Dong-Meng Zhou^{1

2}, Chun-Lin Wang^{1

2}, Chun-Yan Zhao¹, Bing Jia^{1

2}, Jie Qin^{1

2}, Xing-Lin Zhu^{1

2}

Affiliations

¹ Key Laboratory of Ecohydrology of Inland River Basin, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, China.
² Faculty of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China.
³ Faculty of Resources and Environment, Baotou Teachers' College, Inner Mongolia University of Science and Technology, Baotou, China.

Abstract

As a desert shrub, Haloxylon ammodendron combines ecological, economic, and social benefits and plays an important role in the ecological conservation of arid desert areas. Understanding its physiological characteristics and its mechanism of light energy utilization is important for the conservation and utilization of H. ammodendron. Therefore, we selected five stands (5-, 11-, 22-, 34-, and 46-year-old) of H. ammodendron as research objects in the study and measured their photosynthetic light response curves by a portable open photosynthesis system (Li-6400) with a red-blue light source (6400-02B). Then, we measured the leaf chlorophyll parameters in the laboratory, calculated the photosynthetic characteristics by using Ye Zipiao's photosynthetic model, analyzed their variation patterns across stand ages, and explored the relationships between leaf chlorophyll parameters and photosynthetic characteristics. The results showed that leaf chlorophyll parameters and photosynthetic characteristics of H. ammodendron at different stand ages were significantly different. Chl content, P _nmax, and LUE_max of H. ammodendron were V-shaped with the increase of stand age. The 5-year-old H. ammodendron was in the rapid growth period, synthesized more Chl a+b content (8.47 mg g^-1) only by using a narrower range of light, and the P_nmax and LUE_max were the highest with values of 36.21 μmol m^-2 s^-1 and 0.0344, respectively. For the 22-year-old H. ammodendron, due to environmental stress, the values of Chl a+b content, P _nmax, and LUE_max were the smallest and were 2.64 mg g^-1, 25.73 μmol m^-2 s^-1, and 0.0264, respectively. For the older H. ammodendron, its Chl content, P _nmax, and LUE_max were not significantly different and tended to stabilize but were slightly higher than those of the middle-aged H. ammodendron. On the other hand, the other photosynthetic parameters did not show significant variation patterns with stand age, such as R _d, AQE, LSP, LCP, and I _L-sat. In addition, we found that the relationships between Chl a+b content and P _nmax and between Chl a+b content and LUE_max were highly correlated, except for the older H. ammodendron. Thus, using leaf chlorophyll content as a proxy for photosynthetic capacity and light use efficiency should be considered with caution. This work will provide a scientific reference for the sustainable management of desert ecosystems and vegetation restoration in sandy areas.

Keywords: Haloxylon ammodendron; leaf chlorophyll parameters; maximal net photosynthetic rate (Pnmax); maximum light energy use efficiency (LUEmax); stand age.