Environmental history affects the growth and photosynthesis of a green‐tide macroalgae Ulva prolifera

Abstract

In order to understand how the environmental history (low-light and low-temperature history) influences the photosynthetic physiology and metabolism of Ulva spp., we cultured Ulva prolifera seedlings under low-light (LL: 30–50 µmol m−2 s−1) and low-temperature (LT: 10°C) conditions for 3 and 8 days firstly; then, both the LL- and LT- grown seedlings were transferred to optimal conditions (25°C; 120–130 µmol m−2 s−1) for 3 days. During the stress and recovery period, the seedlings grown under 25°C and 120–130 µmol m−2s−1 were set as the control treatment (noted as 25–25°C). The results showed that compared with the control treatment, U. prolifera exhibited pronounced over-compensatory growth induced by low temperature, rather than the low light, but there were no significant differences between 3 and 8 days for low-temperature pretreatments. Based on the results, we cultured this species under 10, 12, 15 and 10–12–15°C firstly and then transferred them to 25°C, in order to study the effects of the low temperature history. It was found that compared with 25–25°C, the growth of thalli was significantly increased by low temperature history, except for that pre-acclimated to 15°C. The reasons for this increase varied, but not included the chlorophyll a (Chl a), water content, soluble sugar and soluble protein (SPs), because the Chl a content was significantly decreased by low temperature history, especially pre-acclimated to 10°C and 10–12–15°C. There were no significant effects of low temperature history on the water content and soluble sugar, while compared with 25–25°C, lower temperature history decreased SPs content, except for pre-acclimated to 10°C. Our results suggest that environmental history, especially low temperature history, plays an important role in the rapid growth of Ulva species.