| Caulerpa lentillifera is an edible green alga with high nutritional value.At present,a lot of studies have been done on the effects of environmental factors such as temperature,illumination,salinity and nutrient salt on the growth of C.lentillifera,but no reports have been reported on the inorganic carbon utilization of C.lentillifera and the addition of exogenous carbon sources on the growth and biochemical components of C.lentillifera.Therefore,in this study,on the basis of verifying that C.lentillifera can utilize HCO3',the method of using HCO3-at different temperatures of C.lentillifera was studied by adding inhibitors.Secondly,the effects of adding an inorganic carbon source NaHCO3 under two kinds of light on the growth,biochemieal components,antioxidant system and nutrient absorption of C.lentillifera were studied.Finally,the NaHCO3 concentration,illumination,temperature and nitrate concentration were optimized during the culture of C.lentillifera.Thus,the physical and chemical conditions favorable for the growth of C.lentillifera were obtained,so as to provide a theoretical basis for large-scale artificial cultivation of C.lentillifera,and also a theoretical reference for other marine green algae to use NaHCO3 as an exogenous inorganic carbon source.The main results are as follow1.The effects of algal weight,algal body parts,illumination and seawater volume on pH compensation point were explored by using the pH drift technology,and the effects of four inhibitors 4,4,-diisothiocyano-stilbene-2,2,-disulfonate(DIDS),acetazolamide(AZ),6-ethoxyzolamide(EZ),vanadate(Van)on the utilization of inorganic carbon in C.lentillifera under three different temperatures(20,25,30?)were analyzed.The results showed that algal weight,algal body parts,illumination,and seawater volume had no significant effect on the pH compensation points(P>0.05).The heavier algal and the stronger illumination made the shorter time of reach the pH compensation point within a certain range,and the pH compensation point is greater than 9.The inhibitory effect of each inhibitor was the highest at 20°C,followed by 30? and 25?,but there was no significant difference between the inhibitors at three temperatures(P>0.05).Among the four inhibitors,DIDS had no significant effect on the pH compensation point and inorganic carbon utilization of C.lentillifera(P>0.05),and the inhibition effects of the remaining three inhibitors were as follows:EZ>AZ>Van.The algae weight,algal body parts,irradiance and seawater volume had no effect on the pH compensation point of C.lentillifera.The temperature had no significant effect on the utilization of inorganic carbon by C.lentillifera.In addition,the present study found that HCO3-can be used as an inorganic carbon source for photosynthesis by C.lentillifera,and mainly based on extracellular CA pathway,but can't directly absorb HCO3-in seawater through DIDS sensitive mechanism.2.The effects of different NaHCO3 concentrations(0,1,2,4,6,8,10 mmol·L-1)on the growth,biochemical components,antioxidant system and nutrient absorption of C.lentillifera under two light conditions(blue-red light(5:1),white light)was studied.The results showed that the addition of NaHCO3 under the two light conditions had no significant effect on the growth of original erect branch,soluble protein content,total N content and C/N of C.lentillifera(P>0.05),and there was no significant difference in the growth of regenerated stolons under the treatment of white light with different NaHCO3 concentrations(P>0.05).The specific growth rate(SGR),wet weight and length of regenerated erect branch,photosynthetic pigment content,soluble carbohydrate content,absorption rate of NO3-and PO43-,nitrate reductase activity of C.lentillifera showed the same trend under the two light conditions.Both increased and then decreased with the increase of NaHCO3 concentration,in the white light adding 6 mmol·L-1 NaHCO3 group,in the blue-red light adding 4 mmol·L-1 NaHCO3 group has a maximum value,respectively,and significantly greater than the control group(P<0.05).The MDA content,T-SOD and CAT activities were the lowest in the white light adding 6 mmol·L-1 NaHCO3 group and in the blue-red light adding 4 mmol·L-1 NaHCO3 group.When adding 8 and 10 mmol·L-1 NaHCO3,MDA content,T-SOD and CAT activity were significantly increased under the two light conditions.It can be seen that appropriate supplementation of NaHCO3 is beneficial to the growth,biochemical accumulation and nutrient absorption of C.lentillifera.Comprehensive analysis showed that the optimal NaHCO3 concentration in the culture of C.lentillifera under white light and blue-red light was 6 mmol·L-1 and 4 mmol·L-1,respectively.3.In order to optimize the culture conditions of C.lentillifera,four physicochemical factors,including NaHCO3 concentration,illumination,temperature and nitrate concentration were selected under white light to conduct four-factor and three-level orthogonal experiments to investigate their effects on the growth and biochemical components of C.lentillifera.The results showed that the SGR of C.lentillifera was the highest under the condition of NaHCO3 concentration of 5 mmol·L-1,illumination of 3000±1000 lx,temperature of 30? and nitrogen concentration of 7 mg·L'1.The regeneration erect branch of C.lentillifera was the longest under the condition of NaHCO3 concentration of 7 mmol·L-1,illumination of 3000±1000 lx,temperature of 27.5? and nitrogen concentration of 7 mg·L-1.Considering the overall growth of C.lentillifera and the growth of regeneration erect branch,showed that NaHCO3 concentration of 6 mmol·L-1,illumination of 3000±1000 1x,temperature of 27.5? and nitrogen concentration of 7 mg·L-1 was the optimal growth condition of C.lentillifera.The soluble carbohydrate content of C.lentillifera was the highest under the condition of NaHCO3 concentration of 7 mmol·L-1,illumination of 3000±1000 lx,temperature of 25?and nitrogen concentration of 15 mg·L-1.The soluble protein content of C.lentillifera was the highest under the condition of NaHCO3 concentration of 6±1 mmol·L-1,illumination of 3000±1000 lx,temperature of 25? and nitrogen concentration of 15 mg·L-1.Comprehensive analysis showed that NaHCO3 concentration of 7 mmol·L-1,illumination of 3000±1000 lk,temperature of 25? and nitrogen concentration of 15 mg·L-1 was the optimal conditions for biochemical components accumulation of C.lentillifera. |
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