Photosynthetic responses of a salt secretor mangrove, Avicennia germinans, exposed to salinity stress

Abstract

In the present study, the effect of variable salinity (0, 15 and 60‰ NaCl) on photosynthetic apparatus was studied in plants (Avicennia germinans seedlings) of a salt secretor mangrove, by measuring chlorophyll fluorescence parameters and gas exchange. Plants treated with NaCl showed a decrease in the maximum net photosynthetic rate (P _n) and stomatal conductance (g _s) as salinity increased from 0 to 60‰. The yield for primary photochemistry (TRo/ABS) and the efficiency with which a trapped exciton can move an electron into the electron transport chain (ETo/TRo), the performance index of Photosystem II (PI_ABS), and the total number of active reaction centers per absorption (RC/ABS) also decreased when exposed to the highest salinity stress (60‰). These results indicated that the main targets in PSII affected by elevated salinity were inactivation of reaction centers and inhibition of the electron transport at the acceptor side of Photosystem II.

Keywords:

• Photosystem II
• chlorophyll a fluorescence

Acknowledgements

The authors appreciate Jose Francisco Rodriguez, Reyna Collı, Jose Luis Febles, Jorge Novelo and Dr. Eduardo Batllori for assistance in seedling cultivation and experimental analysis, and CONACyT (160136).