Threshold effects of photosynthetic efficiency parameters of wild jujube in response to soil moisture variation on shell beach ridges, Shandong, China

Abstract

To investigate the threshold effects of photosynthetically active radiation (PAR) and soil mass water content (MWC) on photosynthetic efficiency parameters of Ziziphus jujuba Mill var. spinosa and to understand the adaptability of Z.jujuba to light and soil moisture variation, we determined optimal MWC and PAR for Z. jujuba which maintained higher net photosynthetic rate (P_N) and water use efficiency (WUE). Using a Li-6400 portable photosynthesis system, we measured light response of P_N, transpiration rate (E), WUE, and other gas-exchange parameters of 3-year-old Z. jujuba shrubs in a range of soil moisture conditions. The results showed that the leaf photosynthetic rate and WUE of Z. jujuba had a significant response to MWC and PAR. Given increases in the MWC (7.1–17.6%), the plant's light compensation point decreased and its light saturation point (LSP), apparent quantum yield, and maximum P_N increased. When MWC was at 17.6%, the low and high light use efficiency of Z. jujuba was all maximal. P_N obviously increased with increasing MWC (9.2–17.6%). However, P_N decreased when MWC was too high or low. When PAR ranged from 800 to 1200 μmol m^− 2 s^− 1, P_N and WUE were higher and the LSPs of P_N and WUE ranged between 706 and 1209 μmol m^− 2 s^− 1. These data indicate that Z. jujuba possessed higher adaptability to light conditions. Based on photosynthetic efficiency parameters, the soil moisture availability and productivity of Z. jujuba were classified and evaluated. For Z. jujuba woodland, MWC < 9.2% and MWC>21.5% resulted in low productivity and medium WUE, 19.8–21.5% of MWC resulted in medium productivity and low WUE, 9.2–11.2% of MWC resulted in medium productivity and medium WUE, and 11.2–19.8% of MWC resulted in high productivity and high WUE. The optimum high productivity and high WUE of MWC were at 17.6%, and the corresponding optimum PAR was 1209 μmol m^− 2 s^− 1.

Keywords::

• Net photosynthetic rate
• Zizyphus jujuba Mill var. spinosa
• water use efficiency
• soil moisture availability
• threshold effect

Additional information

Funding

Funding

The work was financially supported by the National Natural Science Foundation of China [grant numbers 31100468 and 31100196]; by Important National Basic Research Program of China [grant numbers 2012CB416904/zgc and 2013CB430403]; by Science and Technology Plan of Universities in Shandong Province [grant number J13LC03]; by the National Key Science and Technology item in “11th Five Year” period [grant number 2009BADB2B0502]; the Strategic Priority Research Program of the Chinese Academy of Sciences (CAS) [grant number XDA05030404]; One Hundred-Talent Plan of the Chinese Academy of Sciences; the CAS/SAFEA International Partnership Program for Creative Research Teams, the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists [grant number 2012T1Z0010]; the Science and Technology Development Plan of Shandong Province [grant number 2010GSF10208]; the Science and Technology Development Plan of Yantai City [grant number 2011016]; Yantai Double-Hundred High-End Talent Plan [grant number XY-003-02]; and 135 Development Plan of YIC-CAS.