Gordillo F J, Jiménez C, Chavarría J, Xavier Niell F
Aquatic Systems Group, Agriculture and Environmental Science Department, Queen's University of Belfast, Newforge Lane, BT9 5PX, Belfast, UK,
Photosynth Res. 2001;68(3):225-35. doi: 10.1023/A:1012969324756.
This work describes the long-term acclimation of the halotolerant microalga Dunaliella viridis to different photon irradiance, ranging from darkness to 1500 mumol m(-2) s(-1). In order to assess the effects of long-term photoinhibition, changes in oxygen production rate, pigment composition, xanthophyll cycle and in vivo chlorophyll fluorescence using the saturating pulse method were measured. Growth rate was maximal at intermediate irradiance (250 and 700 mumol m(-2) s(-1)). The increase in growth irradiance from 700 to 1500 mumol m(-2) s(-1) did not lead to further significant changes in pigment composition or EPS, indicating saturation in the pigment response to high light. Changes in Photosystem II optimum quantum yield (F(v)/F(m)) evidenced photoinhibition at 700 and especially at 1500 mumol m(-2) s(-1). The relation between photosynthetic electron flow rate and photosyntetic O(2) evolution was linear for cultures in darkness shifting to curvilinear as growth irradiance increased, suggesting the interference of the energy dissipation processes in oxygen evolution. Carbon assimilation efficiencies were studied in relation to changes in growth rate, internal carbon and nitrogen composition, and organic carbon released to the external medium. All illuminated cultures showed a high capability to maintain a C:N ratio between 6 and 7. The percentage of organic carbon released to the external medium increased to its maximum under high irradiance (1500 mumol m(-2) s(-1)). These results suggest that the release of organic carbon could act as a secondary dissipation process when the xanthophyll cycle is saturated.
这项工作描述了耐盐微藻杜氏盐藻对不同光子辐照度（从黑暗到1500 μmol m⁻² s⁻¹）的长期适应。为了评估长期光抑制的影响，测量了使用饱和脉冲法的氧气产生速率、色素组成、叶黄素循环和体内叶绿素荧光的变化。生长速率在中等辐照度（250和700 μmol m⁻² s⁻¹）下最大。生长辐照度从700增加到1500 μmol m⁻² s⁻¹并没有导致色素组成或胞外多糖进一步显著变化，表明色素对高光的响应已饱和。光系统II最佳量子产率（F(v)/F(m)）的变化证明在700 μmol m⁻² s⁻¹尤其是1500 μmol m⁻² s⁻¹时存在光抑制。对于从黑暗中的培养物，光合电子流速率与光合氧气释放之间的关系是线性的，随着生长辐照度增加变为曲线关系，这表明能量耗散过程对氧气释放有干扰。研究了碳同化效率与生长速率、内部碳和氮组成以及释放到外部培养基中的有机碳变化之间的关系。所有光照培养物都表现出保持6至7的碳氮比的高能力。在高辐照度（1500 μmol m⁻² s⁻¹）下，释放到外部培养基中的有机碳百分比增加到最大值。这些结果表明，当叶黄素循环饱和时，有机碳的释放可能作为一种次要的耗散过程。
