Study On The Response Of The Growth And Photosynthetic Function To Different LEDs Light Qualities In Marine Macroalgae

Light is one of the most important environmental factors that regulates many physiological processes in plants and algae.As a new light device,the application of LED in algal culture is beneficial to energy saving and emission reduction.In addition,it can better configure the light quality in order to improve some components of algae and increase the economic value.The effects of different light qualities on four macroalgal species,Gracilaria lemaneiformis,Ulva lactuca,Hizikia fusiformis and Porphyra haitaneinsis,have been investigated via the measurements of growth rates,photosynthesis and biochemical contents of pigments.The objectives of this study are to assess whether LEDs can be used as a substitute for fluorescent lighting,investigate the change of physiological characteristics of four algae under different light qualities and compare the difference in response of four algae in different light qualities.1.In Gracilaria lemaneiformis and Ulva lactuca,the treatments were designed as five light sources:fluorescent light,red,green and blue LED.P-I curves were measured at the algal respective light qualities in culture(i.e.,fluorescent lamps,white,red,green and blue LED,or all in fluorescent light.The objectives of this study are to investigate the change of physiological characteristics of G.lemaneiformis and U.lactuca under different light qualities and compare the difference in response of G.lemaneiformis and U.lactuca in different light qualities.White LED showed similar effects to fluorescent lamps on the relative growth rates?RGRs?and gross maximum photosynthetic rate(P_max).In addition,green LED contributed to the highest RGRs and P_maxin G.lemaneiformis.Interestingly,when compared with fluorescent lamps,green LEDs resulted in a significantly higher P_max in U.lactuca.Besides,blue LED contributed to the highest RGRs of U.lactuca,while the red LED led to the lowest RGRs of U.lactuca.Overall,our study suggests that green and blue LED are alternative monochromatic light sources to fluorescent lamps in G.lemaneiformis and U.lactuca cultivation,respectively.2.In young sporophytes of Hizikia fusiformis,the treatments were designed as four culture light sources:fluorescent light,red,green and blue LEDs,and three different temperatures:15?,20?,25?.At the end of the cultivation,the growth rate and chlorophyll fluorescence of the algae were measured.The objectives of this study are to investigate the optimal light source and explore the suitable cultivation temperature of young sporophytes of H.fusiformis.The red LED contributed to similar growth rate to that of fluorescent lamps at 15?.It suggested that the red LED alternative monochromatic light sources to fluorescent lamps in the cultivation of young sporophytes of H.fusiformis.From the standpoint of energy-saving,the red LED with cultivation temperature of 15?are the optimal cultivation conditions for the young sporophytes of H.fusiformis.The red LED led to the lowest efficiency of electron transport and the maximum relative electron transport rate,while the blue LED contributed to the the highest efficiency of electron transport and the maximum relative electron transport rate.The efficiency of electron transport value of young sporophytes of H.fusiformis cultured in red LED decreased with temperature.3.In Porphyra haitanensis,the treatments were designed as four culture light sources:fluorescent light,red,green and blue LEDs.At the end of the cultivation,the growth rate,chlorophyll fluorescence,the content of pigments and soluble protein,and the activity of superoxide dismutase were measured.Fluorescent light contributed to the highest relative growth rate P.haitanensis.Among the monochromatic LED light sources,the red LED contributed to the significant higher value of relative growth rate than the blue and green LED.Blue LED culture promoted the content of chlorophyll and carotenoids;green light is more conducive to soluble protein synthesis than red light culture.The superoxide dismutase of P.haitanensis cultured under blue LED was the lowest value among four light source cultivation.The r ETR_m of P.haitanensis cultured in red LED is significantly higher than that of green or blue LED,while the Fv/Fm of P.haitanensis cultured in green LED or blue LED is significantly lower than that of red LED.In general,as a superior light source in seaweed farming,LEDs can be used as a good alternative for fluorescent lamps in the cultivation of marine macroalgae.Blue LED stimulated synthesis of protein and enzymes in red algae Gracilaria lemaneiformis and Porphyra haitaneinsis while blue LED reduced growth rate and photosynthetic rate.In brown algae Hizikia fusiformis,blue LED light promoted photosynthetic rate.The green LED light improved the photosynthetic rate of the red algae Gracilaria lemaneiformis,Porphyra haitaneinsis,and the green algae Ulva lactuca.There were different physiological response to light quality in different marine macroalgae species.