硝氮和紫外辐射对龙须菜碳氮利用的影响

摘要

【目的】探讨大型海藻龙须菜(Gracilaria lemaneiformis )碳氮利用对紫外辐射(UVR)的响应,揭示可利用氮在其中的调节作用。【方法】设置2种硝氮浓度(低氮,50μmol·L-1；高氮,500μmol·L-1)和3种不同波长的光辐射处理(P,395~700 nm；PA,320~700 nm；PAB,295~700 nm),龙须菜叶状体在上述不同条件下适应培养25 d 后,测定藻体的硝氮和无机碳利用情况。【结果】PA 和 PAB 条件下培养的龙须菜,对硝氮的最大吸收速率显著升高,尤其在高氮条件下升高更加明显。P 条件下,高氮适应培养的藻体硝酸还原酶(nitrate reduscate,NR)活性显著降低；但在 PA 和 PAB 下没有发现这种氮营养史的影响。UVR 显著降低了龙须菜的最大光合固碳速率(P max )和对外源无机碳的半饱和常数(K DIC ),提高了总碳酸酐酶(carbonic anhy-drase,CA)的活性。高氮适应下藻体的最大光合固碳速率和总 CA 活性显著升高,同时半饱和常数显著降低。【结论】UVR 的存在能够促进龙须菜对外源硝氮的吸收利用,抑制海藻光合固碳能力,但可利用氮的加富可以缓解 UVR 对龙须菜光合作用的抑制。%Objective ]To investigate carbon and nitrogen utilization of Gracilaria lemaneiformis responding to ultraviolet radiation (UVR),and reveal the regulation of avail-able nitrogen in this process.[Methods]Two nitrate treatments with different concentration (L-N,50 μmol·L-1 and H-N,500 μmol·L-1 )and three radiation treatments with different without UVR.UVR exposure decreased the maximal photosynthetic carbon fixation rate (P max )and semi saturation constant of carbon utilization (K DIC ),while raised carbonic anhy-drase (CA)activity in alga.Compared to L-N condition,both P max and CA activity in-creased,and K DIC decreased significantly in thalli cultured in H-N condition.[Conclusion]These results suggested that UVR exposure stimulated nitrogen uptake and inhibited carbon utilization in Gracilaria lemaneiformis .However enrichment of available nitrogen could al-leviate the inhibition on photosynthetic carbon fixation caused by UVR exposure.