The Response Of Spirulina Platensis To Low Temperature And High Light In An Alkali Lake Of The Erdos Plateau

As an economically important alga, Spirulina platensis’s metabolic response toenvironmental changes is the focus of many current researches. The breeding species usedin the domestic factory was originated from tropical regions, thus is sensitive to cold; forthis reason the Spirulina cultivation factory were mostly located in southern China, andconsequently the development of breeding industry in the north was seriously hampered.The output of Spirulina culture in greenhouses at Erdos in northern China is drasticallydropped during the early spring and late autumn when the species from Chad was used dueto the poor fitness, while the Spirulina platensis from an alkaline lake of Erdos Plateaushowed good adaptability with the seasonal changes.This project using the species of Spirulina platensis from the alkaline lake of ErdosPlateau and from the lake of Chad Africa as experimental subjects systematicallycharacterized the growth, photosynthesis, autioxidant enzyme activities at the conditionssimulating the stress of low temperature and high lights and compared the differences ofstress responses between Spirulina platensis from an alkaline lake of Erdos Plateau andspecies from Chad. In addition, the correlation between output variation and changes intemperature and light intensity of Spirulina platensis from an alkaline lake of ErdosPlateau in greenhouse culture was analysised. The results are summarized as following:1. The photoinhibition of Spirulina was significant under the stress of low temperatu-re and high light, the photosynthetic rate dropped drastically with lowering of temperatureand longer treating time; the recovery rate for the treated samples varied with wavelengths,with the blue light showing the most remarkable, followed by red light, yellow light, andgreen light; After stressed by low temperature and high light, the recovery of physicalindexes for samples from Erdos Plateau was faster than that of species from Chad; therecovery time negatively correlated with the treating time and the treating temperature;protein biosynthesis involved in recovery of photosynthetic capacity of Spirulina.2. The chlorophyll a, soluble sugar, soluble protein, PC, APC, and carotenoid decreasedunder the stress of low temperature and high light; the algal filaments was found broken invarious degrees after treated with low temperature and high light accompanied by the color change from dark to lighter, the degree of bleaching was higher for species from Chad thanthat for samples from Erdos Plateau.3. The structure and function of plasma membrane of Spirulina was damaged causedby photo oxidation under the stress of low temperature and high light. The permeability ofplasma membrane, the relative conductivity, the content of malondial-dehyde (MDA), andfree proline increased with lower temperature and longer irradiation; as the stressaggravated, the level of photo oxidation of Spirulina platensis was deeper also, the level ofphoto oxidation of Spirulina platensis from Chad higher than samples from Erdos Plateau.4. The chlorophyll a, protein content, and ATP activity of thylakoid membrane ofSpirulina platensis from Erdos Plateau was found relatively to be more stable than that ofsamples from Chad under stress, indicated by smaller variation ranges. The ATP activitywas stable with the temperature in the range of5℃～30℃. The SDS-PAGE showed thatlow temperature and high light stress induced a new protein band with a molecular weightof42.18kDa.5. The activity of CAT and SOD of the samples were positively correlated withtreating time and temperature under high light; the enzymatic activity of Spirulinaplatensis from Erdos Plateau was higher than that of samples from Chad; the activity ofPOD decreased with treating time prolonged.CAT、SOD were the physiological basis ofSpirulina platensis from Erdos Plateau to low temperature and high light.6. The output rate of S1reached the highest when the average illumination per day wasbelow50Klux and temperature was in the range of22～24℃. S1grew well in the lateautumn when the temperature became lower yet the light was sufficient with the outputrate being86.86%of the highest. Thus, S1is a suitable species for cultivation in northernChina because its resistance to high light and low temperature.