| Light is a one of most important environmental conditions affecting the growth and photosynthesis of marine macroalgae.The marine macroalgae are always grown under changing light conditions?such as the change of light intensity and light quality?..In this study,the main macroalgal species for cultivation the coastal waters in South China,Gracilaria lemaneiformis and Porphyra haitanensis,and the ecological common type species,Ulva lactuca,were used the research materials.Through laboratory controlled culture,and using eco-physiology,morphology,and biochemical analysis techniques,this study had examined the effects of the changes of light,and the interaction of that and other environmental factors?temperature,salinity,nutrients,etc.?on the growth,photosynthesis and related important metabolic functions such as active oxygen metabolism in marine macroaglae.The interspecific competition in different light quality between economic seaweeds and other algae was also explored.Moreover,this study examined the growth and photosynthetic functions of macroalgae cultured under LED light source,and thereby evaluated the potential application of cultivation technology using LED light source in marine macroaglae.The results showed that the growth rate and photochemical activities of G.lemaneiformis were significantly inhibited by high light level of 270 ?mol·m-2·s-1,and such inhibition was more pronounced at a high temperature of 31 ? in the culture.Also,at these condtions,the total photosynthetic pigments contents,especially the phycobiliprotein contents,were significantly decreased.The antioxidase activities of G.lemaneiformis were induced in high light in medium temperature of 18 ? culture.However,the SOD and CAT activities of G.lemaneiformis were reduced at high temperature cultivation,indicating the the algal cells function were damaged in extreme environments.Photochemical activities of both G.lemaneiformis and P.haitanensis were significantly inhibited in low salinity of 10 and hypertonic of 50,while the SOD and CAT activities,and LPO level were significantly increased.The high light level of 270 ?mol·m-2·s-1 induced excessive ROS formation in G.lemaneiformis and P.haitanensis,and a synergistic effect was observed of high light level and extreme osmotic pressure.The results showed that G.lemaneiformis has relaive high light energy utilizationcapacity and growth rate when grown under blue,green and blue + green LED light.For U.lactuca,however,higher photosynthetic efficiency was found in the algae grown under red LED and fluorescent light conditions.The stronger blue-green light using ability was observed in G.lemaneiformis than U.lactuca,but U.lactuca has a relatively stronger red light using ability,showing that thers two species had different light utilization ability probably due to their different light receptors.Growth rate and photosynthetic efficiency of U.lactuca was generally higher than those of P.haitanensis under different LED light source conditions.U.lactuca might have the competitive inhibition effect on P.haitanensis,especially under red light and fluorescent light.High temperature significantly inhibited the growth,photochemical activities and photosynthetic capacity of G.lemaneiformis,and such inhibitory effect was more obvious under red LED light culture.SOD and CAT activities of G.lemaneiformis were significantly induced when grown at 31 ?.SOD and CAT activities of G.lemaneiformis were significantly induced when grown at 17 ?,but not when grown at31 ?,with blue light and red light in cuture.This study provided an important theoretical basis for the further understanding of the photo-biological characteristics in marine macroalgae.This study showed that the responses of the growth and physiology of marine macroalgae to light conditions were depended on the other important ecological conditions,such as temperature and salinity.At the same time,this study provided an important theoretical basis for the application of LED light source control technology on seaweed cultivation.The LED light source control technology is a new method that has many outstanding advantages,i.e.energy saving,environmental protection,economic effective and simple.It will have broad prospects in the field of aquaculture and environmental protection. |
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