Comparison of the photosynthetic efficiency, agar yield, and properties of Gracilaria salicornia (Gracilariales, Rhodophyta) with and without adelphoparasite

Abstract

The red seaweed Gracilaria salicornia is widely distributed along the Gulf of Thailand and Andaman sea coast. In nature, the adelphoparasite Gracilaria babae is mostly found to grow on this alga, and it appears as a gall with dark green or yellowish orange color. This study was conducted to examine the photosynthetic efficiency, agar yield, and properties of G. salicornia in plants with (PGs) and without the adelphoparasite (Gs). The results showed that the photosynthetic efficiency of the PGs and Gs was influenced by environmental factors. The agar yield extracted from the Gs was mostly lower than that from the PGs. The gelling temperature of agar solution from the PGs was lower than in the Gs but was not significantly different (p > 0.05). The gel melting point and the viscosity of the agar solution of the PGs was significantly higher than those of the Gs (p < 0.05). The gel strength and total carbohydrate content of the PGs agar were higher than those obtained from the Gs agar, except for the sample collected in June. The content of 3,6-anhydrogalactose was higher in the PGs than in the Gs collected in February and August, when the PGs agar had greater gel strength. Similarly, the PGs agar had a higher sulfate content than did the Gs agar. This study showed that changes in the photosynthetic efficiency, yield, and properties of agar extracted from G. salicornia were influenced by the environmental factors in association with the presence of the adelphoparasite G. babae.