Effects of Light Intensity and Nitrate Concentration on the Growth and Pigment Composition of Hincksia mitchelliae（Phaeophyceae）
Date Issued
2007
Date
2007
Author(s)
Chang, Yu-Hui
DOI
zh-TW
Abstract
本研究培養棲狀褐茸藻Hincksia mitchelliae，藉不同光強度與氮營養鹽濃度來尋找最適生長的條件與分析藻色素的變化，並比較實驗室馴化多年的藻株與野生藻株形態上的差異來確認種別。以評估其作為商業開發藻褐素生產之可行性。從野外分離之藻株在實驗室環境下培養，藻株形態會從長絲狀轉變為星狀叢生，其藻體細胞的長寬比例也從3.6倍縮為3倍。研究中鑑定出棲狀褐茸藻主要的12種色素種類，除葉綠素a, c1及三種葉綠素a類似物外，尚有藻褐素為含量最高的類胡蘿蔔素。在實驗所測試的硝酸氮濃度( 0~2.4 mM )範圍內，十八天內並未發現到生長有顯著性影響，各色素與葉綠素間比值同樣也不受到影響。然而在較高光強度下棲狀褐茸藻平均日增重率較高，其藻體內葉綠素a與藻褐素的含量變少；然而，藻褐素與葉綠素a含量比值隨著光強度的提升而增高。為避免高細胞密度所造成透光率的不足，而影響色素組成，藉稀釋培養方式來維持一定的中心光照強度，結果顯示照度提升時，其藻褐素與葉綠素含量均下降，但是其間比值卻提升。推測藻褐素在棲狀褐茸藻體內所扮演的角色，除了做為光合作用的吸光輔助色素，也可能與光保護機制有關。棲狀褐茸藻在低密度（1 g/1.6L）培養時，予以低照度6000 Lux，維持較好的生長；但在高密度（10 g/1.6L）培養時，則予以較高光強度20,000 Lux，並充分供應硝酸營養鹽，有最佳生長，而隨著藻細胞密度增加，照度減少，可提升藻褐素含量。
英文摘要
Lab cultures of Hincksia mitchelliae were studied for the effects of light intensity and nitrate concentration on their growth. Field-collected specimens were also cultured to compare the morphological changes during lab condition. It was observed that the long filaments of field specimen turned short and become aster-clusters. The length/width ratio of the cells changed from 3.6 to 3. In this study, twelve pigments were identified in the acetone extracts. Other than chl a, chl c1, and three chl a congeners, there were seven carotenoids among which fucoxanthin was the most abundant one. It was observed that the growth of H. mitchelliae were not affected by the different nitrate concentrations(0~2.4 mM) in the medium within 18 days, nor the relative pigment content to chlorophyll a.
However, it was found that the growth were significantly affected by the light illumination, stronger the light intensity higher the average weight gain. Both fucoxanthin and chlorophyll a declined under stronger light intensity, but the ratio of fucoxanthin to chlorophyll a raised at higher light intensity.
To avoid the cell concentration from the enhancement of high light intensity shaded the following growth and pigment composition response, we used the various degree of dilution to maintain the constant cell concentration during experiment period. We found the pigment declined with the increase of light intensity, same as pervious experiments without adjusting cell concentration. It is speculated that fucoxanthin in brown algae is playing as a photosynthesis accessory. Fucoxanthin also plays as a light protection agent, since the ratio of fucoxanthin to chlorophyll a is raised up under strong light intensity.
Subjects
棲狀褐茸藻
色素
光強度
氮營養鹽濃度
Hincksia mitchelliae
pigment
light intensity
Nitrate Concentration
Type
other
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