Abstract:

The effects of CO₂ enrichment on various ecophysiological parameters of tropical seagrass Thalassia hemprichii (Ehrenb.) Aschers were tested. T. hemprichii, collected from a seagrass bed in Xincun Bay, Hainan island of Southern China, was cultured at 4 CO₂(aq) concentrations in flow-through seawater aquaria bubbled with CO₂. CO₂ enrichment considerably enhanced the relative maximum electron transport rate (RETR_max) and minimum saturating irradiance (E_k) of T. hemprichii. Leaf growth rate of CO₂-enriched plants was significantly higher than that in unenriched treatment. Nonstructural carbohydrates (NSC) of T. hemprichii, especially in belowground tissues, increased strongly with elevated CO₂(aq), suggesting a translocation of photosynthate from aboveground to belowground tissues. Carbon content in belowground tissues showed a similar response with NSC, while in aboveground tissues, carbon content was not affected by CO₂ treatments. In contrast, with increasing CO₂(aq), nitrogen content in aboveground tissues markedly decreased, but nitrogen content in belowground was nearly constant. Carbon: nitrogen ratio in both tissues were obviously enhanced by increasing CO₂(aq). Thus, these results indicate that T. hemprichii may respond positively to CO₂-induced acidification of the coastal ocean. Moreover, the CO₂-stimulated improvement of photosynthesis and NSC content may partially offset negative effects of severe environmental disturbance such as underwater light reduction.

Jiang ZJ, Huang XP, Zhang JP (2010) Effects of CO₂ enrichment on photosynthesis, growth, and biochemical composition of seagrass Thalassia hemprichii (Ehrenb.) Aschers. J. Integr. Plant Biol. 52(10), 904–913.