Promoting effect of low concentration strontium on photosynthetic performance of Chinese cabbage seedlings: Combined leaf characteristics, photosynthetic carbon assimilation and chlorophyll fluorescence

Low concentration strontium (LC-Sr) can promote the growth of plants. In order to explore its promoting mechanism from the aspect of photosynthesis, the leaf characteristics, CO 2 assimilation and chlorophyll (Chl) a fluorescence kinetics were investigated with hydroponically LC-Sr-treated Chinese cabbage seedlings. After a 28d treatment to SrCl 2 at different concentrations (0.1, 0.2, 0.5, and 1.0 mmol L -1 ), we observed an increase in the specific leaf weight (SLW) of Chinese cabbage compared with the control group. Notably, as the strontium concentration increased, a more pronounced improvement trend in the contents of Chl and protein in the leaves was observed, contributing to the enhancement of photosynthesis. However, the statistical differences in P n among various LC-Sr treatments were not significant. Nevertheless, the leaf starch content exhibited a significant increase after LC-Sr treatments. Additionally, Chl a fluorescence transient has been used as a sensitive indicator of the promotional effect of LC-Sr on photosynthesis. The results of fluorescence parameters showed that LC-Sr treatments accelerated the light reaction speed of leaves ( T fm , dV/dt o , dVG/dt o ), improved the energy utilization efficiency of photosystem (PSI and PSII) ( ETo/CSo , psi ET , psi RE , delta Ro , phi Ro ), and ultimately enhanced the photosynthetic performance of leaves ( PI abs , SFI abs , DF abs ). The increased RCs/CSo and Sm contributed to the enhancement of the light reaction activity of strontium-treated leaves. The LC-Sr treatments had no interference with the calcium absorption, and notably enhanced the photosynthetic capacity of Chinese cabbage, shedding light on potential benefits of LC-Sr for crop cultivation.