van de Poll Willem H, Janknegt P J, van Leeuwe M A, Visser R J W, Buma A G J
Department of Ocean Ecosystems, Centre for Ecological and Evolutionary Studies, University of Groningen, P.O. Box 14, 9750 Haren, AA, The Netherlands.
J Photochem Photobiol B. 2009 Jan 9;94(1):32-7. doi: 10.1016/j.jphotobiol.2008.09.003. Epub 2008 Sep 16.
The synergistic effects of iron limitation and irradiance dynamics on growth, photosynthesis, antioxidant activity and excessive PAR (400-700 nm) and UV (280-400 nm) sensitivity were investigated for the Antarctic marine diatom Chaetoceros brevis. Iron-limited and iron-replete cultures were exposed to identical daily irradiance levels, supplied as dynamic (20-1350 micromol m(-2) s(-1)) and constant (260 micromol m(-2) s(-1)) irradiance. After acclimation, growth, maximal quantum yield of PSII (F(v)/F(m)), pigment composition, and the activities of the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) were determined. Then, excessive irradiance sensitivity was assessed by monitoring pigment composition, F(v)/F(m) and viability loss during a single excessive PAR and UV treatment. Iron limitation reduced growth rates, F(v)/F(m) dynamics, and cellular pigments pools. Cellular pigment concentrations were higher under dynamic irradiance than under constant irradiance but this difference was less pronounced under iron limitation compared to iron-replete conditions. SOD and APX activities increased during dynamic irradiance under iron limitation, suggesting increased radical formation around PSII. Despite these physiological differences, no effects on growth were observed between constant and dynamic irradiance cultivation in iron-limited and iron-replete cells. The applied culturing conditions did not affect glutathione reductase activity in C. brevis. F(v)/F(m) and xanthophyll de-epoxidation dynamics during excessive irradiance were not different for iron-limited and replete cells and viability loss was not found during excessive irradiance. This study revealed photoacclimation differences between iron-limited and iron-replete C. brevis cultures that did not affect growth rates and excessive irradiance sensitivity after acclimation to constant and dynamic irradiance.
研究了铁限制和光照强度动态变化对南极海洋硅藻短角毛藻（Chaetoceros brevis）生长、光合作用、抗氧化活性以及对过量光合有效辐射（PAR，400 - 700纳米）和紫外线（UV，280 - 400纳米）敏感性的协同作用。将缺铁培养和铁充足培养的藻细胞暴露于相同的每日光照强度水平下，光照以动态（20 - 1350微摩尔·米⁻²·秒⁻¹）和恒定（260微摩尔·米⁻²·秒⁻¹）光照强度提供。适应后，测定生长、PSII的最大量子产量（F(v)/F(m)）、色素组成以及抗氧化酶超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APX）和谷胱甘肽还原酶（GR）的活性。然后，通过监测在单次过量PAR和UV处理过程中的色素组成、F(v)/F(m)和活力损失来评估对过量光照的敏感性。铁限制降低了生长速率、F(v)/F(m)动态变化以及细胞色素库。动态光照下的细胞色素浓度高于恒定光照下，但与铁充足条件相比，铁限制条件下这种差异不太明显。在铁限制条件下，动态光照期间SOD和APX活性增加，表明PSII周围自由基形成增加。尽管存在这些生理差异，但在铁限制和铁充足的细胞中，恒定光照培养和动态光照培养之间未观察到对生长的影响。所采用的培养条件对短角毛藻中的谷胱甘肽还原酶活性没有影响。铁限制和铁充足的细胞在过量光照期间的F(v)/F(m)和叶黄素脱环氧化动态变化没有差异，并且在过量光照期间未发现活力损失。这项研究揭示了铁限制和铁充足的短角毛藻培养物之间的光适应差异，这些差异在适应恒定和动态光照后不影响生长速率和对过量光照的敏感性。
