导　　师： 夏建荣

学科专业： 083001

授予学位： 硕士

作　　者： ;

机构地区： 广州大学

摘　　要： 海洋浮游硅藻是海洋初级生产力的重要组成部分，在海洋碳循环中起着非常重要的作用，其光合固碳过程受到许多海洋环境因子（营养盐的供应、光和CO/_2等）的制约。本研究以海洋硅藻三角褐指藻作为实验材料，研究不同氮磷比与光强、CO/_2对三角褐指藻光合无机碳利用的交互作用。主要研究结果如下： 三角褐指藻的比生长速率在N:P=16:1时最大，高于或低于16:1时最适生长受到氮磷的限制。氮或磷限制导致叶绿素a含量明显下降，对叶绿素c含量没有明显影响。同时氮或磷限制培养下藻细胞pH补偿点、光饱和光合速率（Pm）、光合效率/(α/)也明显下降。磷限制有助于提高细胞对CO/_2的亲和力，但氮限制并没有明显影响。 当培养光强从50到250μmol·m~/(-2/)s~/(-1/)时，不同营养条件培养的三角褐指藻比生长速率均明显增加。在高光强下，藻细胞的PSⅡ的最大光合效率（Fv//Fm），PSⅡ实际光合效率（Yield），光化学淬灭系数（qP）均明显下降，非光化学淬灭系数（qN）则明显上升，但N或P限制培养的藻细胞的qN上升的幅度明显小于营养充足培养。随着培养光强的增加，三角褐指藻的叶绿素含量明显下降，且N限制下叶绿素a含量的下降更明显。高光强导致不同营养条件培养的三角褐指藻的Pm、α和Rd明显下降，光饱和点（Ik）和光补偿点（Ic）明显上升。随着光强的增加不同营养水平培养的藻细胞的胞内外碳酸酐酶活性和质膜氧化还原活性均明显上升，但是N或P限制培养三角褐指藻的K0.5没有受到高光强的明显影响。N限制培养的三角褐指藻的pH补偿点受高光强的影响明显下降，P限制和营养充足培养细胞的pH补偿点则没有明显变化。 当CO/_2浓度从350pp/_m升高到1000pp/_m时，N限制培养的三角褐指藻的比生长速率、Pm、α、叶绿素a和叶绿素c含量没有明显变化。P限制培养的藻细胞的比生长速率和叶绿素c含量也没有受到CO/_2浓度变化的影响，但P限制培养的藻细胞的Pm、α和叶绿素a含量随着CO/_2浓度的升高明显增加。CO/_2浓度加富导致N或P限制培养的三角褐指藻的Fv//Fm、Yield、qP均明显上升。在高CO/_2浓度下，N限制培养的K0.5明显下降，P限制培养的则相反。N或P限制培养的三角褐指藻的胞外CA活性和质膜氧化还原活性均随着CO/_2浓度的增加明显增加。高CO/_2浓度培养三角褐指藻的pH补偿点均有所下降。 以上研究结果表明：1）高于或低于16:1时三角褐指藻的最适生长受到氮磷的限制。在N或P限制的环境中藻细胞可以通过调节叶绿素含量、质膜氧化还原活性和无机碳利用方式以维持适度的生长。2）在N或P限制环境中，高光强导致生长的促进作用被减弱，用于光合作用的能量有所减少，能量的利用效率降低，同时藻细胞提高碳酸酐酶的活性以适应高光强环境。3）CO/_2浓度升高对N或P限制培养的藻细胞的比生长速率没有明显影响，但高CO/_2浓度下，藻细胞光能的利用效率明显提高。在N或P限制条件下，藻细胞可以通过调节无机碳利用方式和碳酸酐酶活性适应高CO/_2浓度环境。 Marine diatoms are the most successful group of algae and their photosynthesisin the oceans is known to be an extremely important component of global carboncycles. Photosynthesis is closely related to inorganic carbon utilization which wasaffected by nutrient supply, light and CO/_2. Interaction of N:P ratios and light, CO/_2onphotosynthetic inorganic carbon utilization in the marine diatom Phaeodactylumtricornutum was investigated in this paper, and the main findings are as follows: The specific growth rate in the algae grown under the medium with N:P=16:1was the largest. Higher or lower than N:P=16:1resulted in a significant decrease,which indicated that the optimum growth was limited by nitrogen or phosphorussupply. Chlorophyll a content decreased in N or P limitation, however the content ofchlorophyll c was significantly affected by N or P limitation. pH compensation point,light-saturated photosynthetic rate and photosynthetic efficiency also reduced in N orP-limited conditions. K0.5CO/_2was decreased in P-limited conditions,butunchangeable in N limitation, which indicated P limitation could increase the affinityfor CO/_2, Under the different nutrient levels, elevated light intensity from50to250molm-2s-1resulted in a significant increase in the specific growth rate. A decrease inFv//Fm, Yield, qP and an increase of qN were also observed in cells grown under highlight intensity. Moreover, qN in N or P-limited conditions rose with the increasedlight levels more slowly than that of nutrient-replete. High light intensity led to adecrease of Pm, α and Rdand an increase of Ikand IC. With the increase of light levels,carbonic anhydrase activity and plasma membrane redox activity rose significantly.However, K0.5was not affected by high light intensity in N or P-limited conditions.pH compensation point in high light levels had a obvious decline in N limitation, andkept constant in P limitation. The specific growth rate, Pm,, chlorophyll a and c content in N-limited cellswere not affected by CO/_2enrichment. Under P-limited condition, Elevated CO/_2caused unchange of the specific growth rate and chlorophyll c content, but Pm, andchlorophyll a content increased with the elevated CO/_2. CO/_2enrichment led to asignificant increase in Fv//Fm, Yield and qP under N or P-limited condition. K0.5declined significantly in N-limited conditions, but the opposite result was observed inP-limited conditions. Extracellular carbonic anhydrase activity and plasma membraneredox activity in N or P limitation increased with CO/_2enrichment, but pH compensation point declined. The above results showed that1/) The optimum growth in Phaeodactylumtricornutum was limited by nitrogen or phosphorus supply when N:P ratio was higheror lower than=16:1, and this alga grown under conditions of nutrient limitation /(N orP/) could maintain a moderate growth by adjusting chlorophyll content, the mode ofinorganic carbon utilization.2/) Under N or P-limited conditions, high light intensityweakened the growth, and decreased energy for photosynthesis and energy utilizationefficiency. In the meantime, carbonic anhydrase activity was increased to adapt tohigh light conditions.3/) The specific grwoth rate in N or P-limited cells was notaffected by CO/_2enrichment, however, the effiency of energy utilization increased.The affinity for inorganic carbon and carbonic anhydrase activity in Phaeodactylumtricornutum cultured under N or P limitation were regulated to adapt to the elevatedCO/_2condition.

关 键 词： 三角褐指藻 无机碳利用 氮磷比 光强 二氧化碳

分 类 号： [Q945]

领　　域： [生物学]