Desiccation effect on the PSII photochemical efficiency of cultivated Japanese Caulerpa lentillifera under the shipping package environment

In Japan, fresh cultivated green alga, Caulerpa lentillifera (Caulerpaceae, Bryopsidales), are packed into polystyrene containers without seawater. They can stay fresh for 1 week inside the container under room temperature, suggesting a high tolerance to desiccation. This tolerance was evaluated in the present study by employing methods based on pulse amplitude modulation (PAM) fluorometry. The chronological change of the photochemical efficiency of photosystem II (PSII) of C. lentillifera in response to desiccation under conditions experienced during the commercial shipping was examined. Desiccation experiments were carried out for 2, 4, 8, and 12 days at 20 °C. Maximum quantum yields (Fv/Fm) were measured at the initial state, after each desiccation period, and after 10-min and 3, 6, and 24-h re-immersion in seawater. Fv/Fm of samples after a 2-day desiccation remained relatively high (0.78 ± 0.04 standard deviation (SD)), while those after 4- and 8-day desiccation periods decreased and yet were considered active with values greater than 0.40 following rehydration. Samples under the 12-day desiccation had the greatest decline in Fv/Fm, (0.10 ± 0.10), along with 72% critical water loss. Failure of the seaweed to recover from desiccation stress further indicates deactivation of the photosystem, which is perhaps associated with multiple cellular alterations that result at the end in a dysfunctional alga. The packaging system that makes use of polystyrene containers for thermal insulation and an absorbent sheet for moisture control may have provided an optimal environment for the seaweed to extend its “freshness” up to 1 week by maintaining photochemical efficiency.