Effect of light intensity on the photosynthetical responses ofGracilaria lemaneiformisin non-aerated and aerated cultures

Abstract

The economic red macroalga Gracilaria lemaneiformis was selected to study light intensity effects on its grow th,photosynthesis,effective quantum efficiencies( Yield) and pigments contents in aerated and non-aerated cultures. Three different light intensities w ere as follow s: 50 μmol /( m2· s)( low light intensity),100 μmol /( m2·s)( moderate light intensity),and 200 μmol/( m2·s)( high light intensity). The results show ed that the highest grow th rate of G. lemaneiformis w as observed w hen alga w as treated w ith moderate light intensity,and too low or too high light intensity inhibited its grow th. The relative grow th rates of aerated cultured algae,under the low light intensity,moderate light intensity and high light intensity,w ere increased by 26. 85%,31. 82% and 40. 56%,respectively. In aerated culture,the photosynthetic rate and the photosynthetic efficiency of alga treated w ith low light intensity increased by 8. 14% and 4. 26%,and the respiration rate of alga under high light intensity decreased by 20. 70%,and Yield increased by 44. 16%. The results suggested that reduced grow th w as mainly due to the limited photosynthesis in case of low light intensity,or could be ascribed to the increased respiration in case of high light intensity. Aerated culture could relieve the negative effect on the grow th rate of alga as a result of for low light or high light intensity.