Hardening‐off under fluctuating light enhances the photosystem I resistance to excessive fluctuating light in <i>Enhalus acoroides</i>

Seagrass meadows of Enhalus acoroides are rapidly declining. Transplanting artificially cultured seedlings is considered an efficient method of seagrass restoration. However, excessive fluctuating light (eFL) in the wild is highly likely to be a major threat to the survival of transplanted seedlings of E. acoroides. This study demonstrated that eFL in the wild inhibited the development of PSI activity in mature E. acoroides plants but had little effect on PSII activity. To verify the effect of FL on artificially cultured seedlings of E. acoroides, we cultured such seedlings under FL and constant light (CL) indoors. The results showed that the PSI activity of FL-cultured seedlings was lower than that of CL, while the resistance of PSI to eFL was significantly enhanced in FL-cultured seedlings. The increase in PSI resistance of FL-cultured seedlings was attributed to the decrease in active PSII reaction centers, which protected PSI from excessive electrons at the moment when low light turns to high light. This study demonstrated that using FL to cultivate E. acoroides seedlings can improve their adaptability to eFL in the wild, as a possible way to increase the survival rate of transplanted seedlings.