高浓度CO2与磷浓度对葛仙米生长和光合作用的耦合效应

在不同CO₂(400和2000 ppm)和磷浓度下(0.088—0.350 mmol/L)培养葛仙米(拟球状念珠藻, Nostoc sphaeroides Kutzing), 研究CO₂和磷对葛仙米相对生长速率、色素含量、光系统Ⅱ光化学活性和光合速率等的影响。结果显示CO₂或磷浓度对葛仙米的相对生长速率、球体粒径和数量、光饱和光合速率、呼吸速率和光合效率均有显著影响, 且两者对球体粒径和数量、叶绿素a含量、呼吸速率和光合效率存在明显交互作用。高CO₂浓度培养明显提高磷对球体粒径和数量和光合效率的效应, 同时降低高磷浓度对叶绿素a合成的抑制作用, 但两者对相对生长速率、藻胆蛋白含量、光饱和光合速率、F_v/F_m和Yield的交互作用均不显著。以上研究结果表明高CO₂浓度或磷浓度增加促进葛仙米生长主要是通过提高光合速率和光合效率来实现; 两者交互作用表明高CO₂浓度可能通过提升磷的利用效率, 降低高磷浓度对叶绿素a合成的抑制, 提高光合效率, 使球体明显增大。

INTERACTIVE EFFECTS OF ELEVATED CO2 AND PHOSPHORUS ON THE GROWTH AND PHOTOSYNTHESIS IN NOSTOC SPHAEROIDES

Nostoc sphaeroides is an edible nitrogen-fixing cyanobacteria in paddy fields with high economic values. However, little is known about its physiological response to CO₂ and phosphorus which are essential for the growth of N. sphaeroides. In this study, we cultured N. sphaeroides at two levels of pCO₂ (400 and 2000 ppm) and different phosphorus concentrations (0.088—0.350 mmol/L) to investigate the interactive effects of CO₂ and phosphorus on the relative growth rate, pigment content, photochemical activity of PSII and photosynthetic rate. The results showed that individual CO₂ or phosphorus concentrations had significant effects on the relative growth rate (RGR), particle size and mass, light-saturated photosynthetic rate (P_m), dark respiration rate (R_d) and photosynthetic efficiency (α) of N. sphaeroides. Furthermore, CO₂ and phosphorus had obvious interaction on its particle size and mass, chlorophyll a content, dark respiration rate and photosynthetic efficiency. High CO₂ concentration significantly increased the effect of phosphorus on the particle size and mass, dark respiration rate and photosynthetic efficiency, and decreased the inhibitory effect of high phosphorus concentrations on chlorophyll a synthesis. In addition, the interactions of CO₂ and phosphorus on the relative growth rate, phycobiliproteins content, light-saturated photosynthetic rate, the maximum photochemical efficiency (F_v/F_m) and actual photochemical efficiency (Yield) were not significant. The results suggest that elevated CO₂ or high phosphorus concentrations promoted the growth of N. sphaeroides mainly by enhancing photosynthetic rate and photosynthetic efficiency. The interaction between CO₂ and phosphorus concentrations indicated that high CO₂ concentration may increase the utilization efficiency of phosphorus, and reduced the inhibition of chlorophyll a synthesis by high phosphorus concentration to improve photosynthetic efficiency.