Differences in photosynthetic behaviour of Kappaphycus alvarezii and Kappaphycus striatus during dehydration and rehydration

Abstract

The kappa-carrageenan-producing seaweed Kappaphycus striatus is different from K. alvarezii in that it grows well in the intertidal zone, where the thalli are exposed periodically to dehydration and rehydration. To investigate the specific tolerance mechanism of K. striatus, the photosynthetic behaviour of K. alvarezii and K. striatus exposed to osmotic variation was compared. K. striatus had a lower dehydration rate in the dark treatments and a higher rehydration rate in both the dark and light treatments as compared with K. alvarezii. The FV/FM of K. striatus was significantly higher than that of K. alvarezii during the process of dehydration and rehydration in both the light and dark treatments. The increase in amplitude of JIP-test fluorescence parameters VK, VJ and VI of K. striatus was smaller than that of K. alvarezii during the dehydration process in both the light and dark treatments. The increased amplitude of VK, VJ and VI in K. striatus was significantly lower than that in K. alvarezii when they were rehydrated in the dark treatments. Therefore, during the process of dehydration and rehydration, the tolerance of the oxygen evolving complex, the ability to balance photosynthetic light absorption and energy utilization, as well as the tolerance of PSII reaction centres were relatively higher in K. striatus compared with K. alvarezii. Such an increased tolerance of PSII may help to improve the tolerance of the whole plant to dehydration.