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 mu mol m(-2) s(-1)) and low-temperature (LT: 10 degrees C) conditions for 3 and 8 days firstly; then, both the LL- and LT- grown seedlings were transferred to optimal conditions (25 degrees C; 120-130 mu mol m(-2) s(-1)) for 3 days. During the stress and recovery period, the seedlings grown under 25 degrees C and 120-130 mu mol m(-2)s(-1) were set as the control treatment (noted as 25-25 degrees 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 degrees C firstly and then transferred them to 25 degrees C, in order to study the effects of the low temperature history. It was found that compared with 25-25 degrees C, the growth of thalli was significantly increased by low temperature history, except for that pre-acclimated to 15 degrees 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 degrees C and 10-12-15 degrees C. There were no significant effects of low temperature history on the water content and soluble sugar, while compared with 25-25 degrees C, lower temperature history decreased SPs content, except for pre-acclimated to 10 degrees C. Our results suggest that environmental history, especially low temperature history, plays an important role in the rapid growth of Ulva species.