AUTHOR=He Xiao-hui , Si Jian-hua , Zhou Dong-meng , Wang Chun-lin , Zhao Chun-yan , Jia Bing , Qin Jie , Zhu Xing-lin 

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

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.967849

DOI=10.3389/fpls.2022.967849

ISSN=1664-462X

ABSTRACT=As a desert shrub, Haloxylon ammodendron combines ecological, economic and social benefits, plays an important role in ecological conservation of arid desert areas. Understanding its physiological characteristics and the 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 photosynthesis-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 photosynthetic characteristics by using Ye Zipiao’s photosynthetic model, and 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, Pnmax and LUEmax of H. ammodendron were V-shaped with the increase of stand age. 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 Pnmax and LUEmax were the highestwith the value of 36.21 μmol m-2 s-1 and 0.0344, respectively. For 22-year-old H. ammodendron, due to the environmental stress, the values of Chl a+b content, Pnmax and LUEmax were the smallest, and were 2.64 mg g-1, 25.73 μmol m-2 s-1, and 0.0264, respectively. For older H. ammodendron, their Chl content, Pnmax and LUEmax were no significant difference and tended to stabilize, but were slightly higher than those of the middle-aged H. ammodendron. Whereas, the other photosynthetic parameters did not show significant variation patterns with stand age, such as Rd, AQE, LSP, LCP, and IL-sat. In addition, we found that the relationships between Chl a+b content and Pnmax, between Chl a+b content and LUEmax were highly correlated, except 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 sustainable management of desert ecosystems and vegetation restoration in sandy areas.