Effect Of Light Intensity On Morphological And Physiological Of Spirulina Platensis

Spirulina platensis is a kind of phototrophic prokaryotes, which is sensitivity to light. It is a kind of microalgae, and has a broad application prospect. S. platensis has strong reproductive capacity, high protein content, and certain health care function, and is easy for large production scale. In this study, Spirulina platensis is used as research materials, research the growth rate of Spirulina platensis, morphological, pigment, phycocyanin, physiological and biochemical characteristics and the effect of different light intensity on morphological. Through the measurement of the growth rate of spirulina, we can find the light intensity has great influence on the growth of spirulina strains. From the fifth day the strain SPC cultured in3000lx got into the log phase earlier, while that cultured in1000lx got into log phase in the sixth day and with one day delay. The maximum relative growth rate of S. platensis in3000lx was nearly1.94time of that in1000lx with28%net biomass increment. Measured the pitch and floating rate of Spirulina All four strains tested tightened their helical pitches by8%～18%and decreased filaments floatation by20%～30%under3000lx illumination. The contents of Chlorophyll a, phycocyanin and allophycocyanin were significantly reduced to17%～89%,19%～68%and13%～47%of those in1000lx respectively; and carotenoid contents were remarkably increased by1.2～4.5times under3000lx. High light intensity is beneficial to the growth of Spirulina and recovery and light is the important factor of the morphogenesis of Spirulina platensis. The filaments in3000lx were more tightened than those under1000lx.In this experiment, the electric conductivity, proline (pro), malondialdehyde (MDA), catalase (CAT) and peroxidase (POD) contents of six strains of S. platensis under strong light stress were determined by colorimetric method,acidity ninhydrin and electric conductivity radiometer, respectively. Under3000lx, the electric conductivity, malondialdehyde, proline and antioxidant enzyme activities of6strains was much higher than those in1000lx light. With the increase of light intensity, the electric conductivity increased up to2～6times and the proline contents of S. platensis increased up to5times; the malondialdehyde contents of S. platensis increased40%～100%; the catalase and peroxidase contents of S. platensis increased19%～80%and20%～100%, respectively. The experiment data showed that S. platensis under light stress initiated certain self-protection mechanisms in order to adapt the environmental changes. So, spirulina filament pitches tightened is the direct adaptability to high light intensity.The purpose of this study is to explain the effect of light intensity on the helical morphological and some physiological changes of S. platensis, and to study the relationship between the morphological changes of cyanobacteria and the light stress. This experiment is also beneficial to find Optimal Production Conditions of High-Yield Polysaccharide in Spirulina and understand the adaptation mechanism of environment.