To investigate the presence and capability of photochemical mechanisms that regulate photosynthesis in outdoor cultures of microalgae, measurable parameters must be acquired on time scale shorter than observable changes in photosynthesis. For this reason, chlorophyll fluorescence may prove a very useful tool in studies aiming to elucidate the effect of rapidly changing environmental factors on the physiology of outdoor cultures of microalgae. Saturating pulse fluorescence technique was applied to study photoinhibition of photosynthesis in outdoor cultures of Spirulina grown under oxygen and temperature stress. Diurnal chages in PSII-photochemistry (Fv/Fm) after 15 min of darkeness or in the light (dF/F'm), and non-photochemical quenching (qN) were measured using a portable, pulse-amplitude-modulated fluorometer. The depression of the Fv/Fm ratio of Spirulina cultures grown under oxygen stress reached 35% at the middle of day. At the same time of the day the dF/F'm ratio showed reduction of up to 60%. The depression of both Fv/Fm and dF/F'm was higher when low temperature (i.e., 10 °C below the optimal value for growyh) was superimposed to oxygen stress. Under these conditions the Fv/Fm and dF/F'm ratios decreased respectively by 50% and by 80%, compared to morning values. Photoinhibition reduced the daily productivity of the culture grown uder oxygen stress by 33% and by 60% in the one grown under either oxygen and temperature stress in summer. Changes, in the growth yields of the cultures grown under different stress conditions and their rates correlate well with analogous changes in photon yield (dF/F'm). Simple measurements of dF/F'm , can be used to test the physiological status of Spirulina cultures. These results indicate that on-line saturating pulse fluorescence technique is a powerful tool for assessment of the photosynthetic performance of outdoor cultures of Spirulina.
On-line monitoring of chlorophyll fluorescence to assess photoinhibition of photosynthesis in outdoor cultures of Spirulina platensis exposed to oxygen and temperature stress
Torzillo G;
1997
Abstract
To investigate the presence and capability of photochemical mechanisms that regulate photosynthesis in outdoor cultures of microalgae, measurable parameters must be acquired on time scale shorter than observable changes in photosynthesis. For this reason, chlorophyll fluorescence may prove a very useful tool in studies aiming to elucidate the effect of rapidly changing environmental factors on the physiology of outdoor cultures of microalgae. Saturating pulse fluorescence technique was applied to study photoinhibition of photosynthesis in outdoor cultures of Spirulina grown under oxygen and temperature stress. Diurnal chages in PSII-photochemistry (Fv/Fm) after 15 min of darkeness or in the light (dF/F'm), and non-photochemical quenching (qN) were measured using a portable, pulse-amplitude-modulated fluorometer. The depression of the Fv/Fm ratio of Spirulina cultures grown under oxygen stress reached 35% at the middle of day. At the same time of the day the dF/F'm ratio showed reduction of up to 60%. The depression of both Fv/Fm and dF/F'm was higher when low temperature (i.e., 10 °C below the optimal value for growyh) was superimposed to oxygen stress. Under these conditions the Fv/Fm and dF/F'm ratios decreased respectively by 50% and by 80%, compared to morning values. Photoinhibition reduced the daily productivity of the culture grown uder oxygen stress by 33% and by 60% in the one grown under either oxygen and temperature stress in summer. Changes, in the growth yields of the cultures grown under different stress conditions and their rates correlate well with analogous changes in photon yield (dF/F'm). Simple measurements of dF/F'm , can be used to test the physiological status of Spirulina cultures. These results indicate that on-line saturating pulse fluorescence technique is a powerful tool for assessment of the photosynthetic performance of outdoor cultures of Spirulina.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
