Clark Darren R, Flynn Kevin J, Owens Nicholas J P
Ecology Research Unit, School of Biological Sciences, University of Wales Swansea, Swansea SA2 8PP, UK.
Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK.
New Phytol. 2002 Jul;155(1):101-108. doi: 10.1046/j.1469-8137.2002.00435.x.
• The ability of the diatom Thalassiosira weissflogii to assimilate inorganic N in darkness is compared with that seen in flagellates. • Experiments were conducted with T. weissflogii grown in N-replete and in N-limiting cultures and the rates and capacity for ammonium and nitrate assimilation were determined. • High daily growth rates in the diatom under high-light nitrate-replete conditions are only attainable by continuing nitrate assimilation in darkness using excess C accumulated in the light when nitrate assimilation cannot match C-fixation. The ability to use ammonium in darkness is greater than for nitrate but the ratio of dark to light assimilation for each N source is similar over a wide range of cellular N : C ratios. These capabilities are in strong contrast with those in the flagellates Heterosigma carterae and Heterocapsa illdefina, which are incapable of high nitrate use in darkness. • While the possession of large capacity for dark nitrate-assimilation in diatoms may provide a mechanism that overcomes nitrate limitation of growth, the explanation for the lower capabilities exhibited by flagellates is less clear.
• 将硅藻威氏海链藻在黑暗中同化无机氮的能力与鞭毛虫进行比较。
• 对在氮充足和氮限制培养条件下生长的威氏海链藻进行了实验，并测定了铵和硝酸盐同化的速率及能力。
• 在高光、硝酸盐充足条件下，硅藻的高日生长速率只有通过在黑暗中利用光照时积累的过量碳持续进行硝酸盐同化才能实现，此时硝酸盐同化无法与碳固定相匹配。黑暗中利用铵的能力大于利用硝酸盐的能力，但在广泛的细胞氮：碳比范围内，每种氮源的黑暗同化与光照同化的比率相似。这些能力与卡特氏异养藻和不规则异帽藻等鞭毛虫形成强烈对比，后者在黑暗中无法高效利用硝酸盐。
• 虽然硅藻拥有大量黑暗硝酸盐同化能力可能提供了一种克服生长中硝酸盐限制的机制，但鞭毛虫表现出较低能力的原因尚不清楚。
