| Microalgae have broad application and development prospects in the food,medicine,new materials and energy due to its high photosynthesis efficiency and growth rate.Changes in temperature and light intensity would change the growth status of microalgae,and the chlorophyll fluorescence kinetic parameters can be used as an intrinsic probe to indicate changes in photosynthesis.In this dissertation,I.zhangjiangensis(WT)and its heat-resistant mutant I.zhangjiangensis IM130005(IM),T.subcordiformis and two common microalgae Nannochloropsis oceanica and Dunaliella salina were used as the research objects.Continuous monitoring of maximum photon conversion efficiency(F_v/F_m)by the self-made microalgae culture automatic control system Algal Station,to investigat the effect of temperature on on the growth and biomass accumulation for I.zhangjiangensis,and explore the heat-resistance mechanism of thr heat-resistant mutant strains;to analyze the Periodic fluctuation rule of chlorophyll fluorescence and the effects of light intensity on cell growth and biomass accumulation of T.subcordiformis;further,to explore the cyclical changes of chlorophyll fluorescence in different microalgae under the same photoperiod.Response of F_v/F_m of heat-resistant strain of I.zhangjiangensis to high temperature stress:A detailed comparison was performed by continuous monitoring cell density(OD),F_v/F_m and fatty acid profile between IM and WT under a mimic temperature shock to the Dalian summer outdoor cultivation.The F_v/F_m and OD changes indicate that the temperature resistanceo upper limit of IM is about 4? higher than that of WT.the F_v/F_m of IM remains around 0.7,with no significant decline at 44?;In IM,the total fatty acid content increased from 12.05 to 14.46%in dry weight within 5 hours with the temperature increasing from 25? to 40? at a rate of1?/20 min,while the neutral lipid(NL)increased 170.06%,It is speculated that IM can alleviate the high temperature energy stress by accelerating the accumulation of TAG.The WT has no such changes.Correlation between different light intensity responses and growth and physiological and biochemical components of T.subcordiformi F_v/F_m:7 kinds of light intensity were precisely controlled,the changes of OD and F_v/F_m in T.subcordiformis were monitored in real time at14/10(light/dark)cycle continuously cultured,further,biomass accumulation and light energy utilization change rule were analyzed.On the whole,the F_v/F_m of the T.subcordiformis showed a change trend of first rising and then fall,and the dark stage was higher than the light stage;at low light intensity(<750?mol/m~2/s)F_v/F_m maintains a good state,and the light energy utilization rate reaches 10%;In the case of medium and high light intensity(750,1000,1500,2000?mol/m~2/s),the light energy utilization rate and F_v/F_m will decrease with the increase of light intensity,but it can still grow normally.The light energy utilization rate is reduced decreased by 23.39%,43.69%,49.65%,58.78%compared with the low light intensity.The fatty acid yield of T.subcordiformis increased at medium and low light intensity(?750?mol/m~2/s)with the increase of light intensity to 125 mg/L/48h;At high light intensity,the yield of fatty acid was around 140 mg/L/48h,and the light intensity 750?mol/m~2/s is determined as the best light intensity in combination with fatty acid yield and light energy input.Periodic fluctuation of F_v/F_m in four common microalgae under conventional cultured:the changes of F_v/F_m in four common microalgae(I.zhangjiangensis,T.subcordiformis,N.oceanica and D.salina)were monitored in real time at 14/10(light/dark)cycle continuously cultured.The thresholds of F_v/F_m in four microalgae were significantly different under 14/10light-dark cycle culture,and each algae had its unique F_v/F_m periodicity variation.This rule can provide a theoretical basis for large-scale controllable culture of microalgae... |
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