大气CO_2浓度增加对生物组织结构与功能的可能影响──Ⅰ─模拟CO_2实验技术以及细胞、叶片和个体生长对CO_2的响应

LIKELY IMPACTS OF RISING ATMOSPHERIC CO_2 CONCENTRATION ON PLANTS AND ECOSYSTEMS I. CO_2 EXPERIMENTAL TECHNIQUES AND RESPONSES OF CELLS, LEAVES AND INDIVIDUAL PLANTS TO CO_2 ENRICHMENT

本文系统综述了大气ＣＯ２浓度增加对植物和生态系统影响的实验技术方法和细胞、叶片和个体水平对ＣＯ２反应的最新研究成果。包括细胞水平上酶的变化；叶片水平的生理反应；个体水平的生长、碳氮分配及相互作用。

An introduction of methodology and techniques being adopted for experimental investigation of plants and ecosystems to elevated CO2, including genetically manipulation, controlled environmental facilities, branch bags or chambers, open-top chambers, free-air controlled enrichment system, natural CO2 vents, and eddy covariance measurement, was briefly made. The ultimate results of internationally current studies on elevated atmosphericCO2 was reviewed with respect to responses of cells, leaves, individual plants. Most early experiments on COZenrichment of trees were done in the same ways on agricultural crops, using potted juvenile seedlings and fixednutrient capital, leading to constrained root groWth, nutrient limitation, poor coupling to the atmosphere and lackof sustained active sinks for photosynthate. Also, these experiments were generally done in the short term, insteadof gradual adaptation and acclimation Processes. All these contribute to a large variations observed inphysiological and growth response of plants to elevated CO2. Elevated COZ induced decrease in stomatalconductance by a range of 10%￣69%, and increase in growth by a range of 20%￣120%. Broad-leaved trees aremore sensitive to elevated CO2 than conifers. Interaction between the responses of plants to elevated CO2 and theavailability of nutrient raise important questions. Changes in the balance between rates of uptake of CO2 and ofinorganic nutrient, especially N, may result in changes in the translocation of carbon and nitrogen within plants.Although nutrient has been increasingly involved in studies of the impact of elevated CO2 on plant growth,andphysiology, the quantitative effects of the rate of supply of nutrients are often neglected in experiment design,leading to difficulties interpreting CO2 responses and interactions between CO2 and nutrition.Recent experiments, by adopting the steady-state nutrition approach, demonstrated that there was no effectof elevated CO, on allocation of carbon between roots and shoots with a high rate of N supply, but that a highfraction of plant dry mass was found in roots, primarily in fine roots when the rate of N-supply was low. Thedown regulation of photosynthesis in parallel by decrease in rubisco activities occurred regardless of nitrogensupply.The acclimation process of photosynthesis to elevated CO2, the mechanism of CO2 regulating stomatalaction, and the long term-effects of interaction between carbon and nitrogen on groWth and physiologicalresponses of plants to elevated CO2 were strongly recommended for future research.