title: Effects of CO(2) enrichment on photosynthesis, growth, and biochemical composition of seagrass Thalassia hemprichii (Ehrenb.) Aschers.
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.
authors.affiliation: South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Zhi Jian
authors.initials: ZJ
authors.lastname: Jiang
authors.forename: Xiao-Pin
authors.initials: XP
authors.lastname: Huang
authors.forename: Jing-Ping
authors.initials: JP
authors.lastname: Zhang
mesh_terms: D002245:Carbon Dioxide / Q000494:pharmacology*; D031321:Hydrocharitaceae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D010788:Photosynthesis / Q000187:drug effects*
chemical_list: D002245:Carbon Dioxide