Fluorescence spectra chlorophyll

A real-time spectral data monitor was placed in operation. The monitor consists of an independent microprocessor-based system that acquires real-time spectral data and additional housekeeping information flowing through the CAMAC/HP computer-interface lines. The complete laser-induced fluorescence spectrum produced by each laser shot is displayed in real time. The system also provides a two-channel output to an analog chart recorder that produces two profile traces (usually the laser-induced phycoerythrin and chlorophyll a spectral response peaks). 

Figure 5. Top Laser-induced spectrum obtained at position a on Flight Line 7 shown in Figure 4 at this ring boundary location the chlorophyll fluorescence was elevated. Bottom Waveform obtained in a low chlorophyll a concentration region within the warmer core of the ring at position Z in...

The initial non-variable (F0), variable (Fv) and maximum (Fmax) yield of chlorophyll fluorescence was measured with intact cells suspended in their growth medium. Actinic excitation was provided in the green region of the spectrum by CS 4-96 and CS 3-69 Coming filters at an intensity of 35 pmol photonsm s 1. 

Two recent works using spectral microscopy have reported dependence of fluorescence spectrum on radial positions in cyanobacterial cells [20, 30], One is about variation between subunits of phycobilisomes in Nostoc punctiforme [20], the other is reporting that phycobilin-to-chlorophyll fluorescence ratio (phycobilin/chlorophyll) is higher along the periphery than inside the cells in Synechocystis sp. PCC6803 [30], The latter phenomenon seems to be opposite to what we have found. How such different trends arise is interesting future subject to be addressed with the help of spectral microscopy. 

The fluorescence spectrum of the Chlorella chloroplast is relatively flat between 715 and 740 nm compared with that of Zea mays, which often shows an increase in fluorescence intensity from 715 to 740 nm. The situation suggests that the far-red component of the Zea mays is substantially influenced by PSI whilst the far-red component ofthe Chlorella is dominated by a vibronic progression ofthe chlorophyll fluorescence of PSII. It is then reasonable that the red and far-red fluorescence images are relatively similar to one another. 

In any case, our results clearly demonstrate that the room temperature fluorescence spectrum of chlorophyll-proteins differs according to the state of both the donor and acceptor sides of PS II reaction center. 

By measuring the chlorophyll fluorescence induction kinetics and the fluorescence spectrum of an intact leaf or plant the condition and potential activity of the photosynthetic apparatus can be estimated (1, ed. H.K. Lichtenthaler). Solely two parameters namely the chlorophyll fluorescence ratio F685/F730 and the fluorescence life time are reliable to measure by remote sensing (2). 

Figure 1 - left — Chlorophyll fluorescence of chloroplasts of a single stomate of NO treated and non-treated pea foliage, as measured by the SpectraCube 1000 system. Each curve is the red fluorescence spectrum of a chloroplast right —... 

The fluorescence spectra of chlorophylls are similar to those of visible absorption. Chlorophyll a shows a higher sensitivity at maximum and minimum wavelengths than that of chlorophyll b. The spectra of pheophytins a and b are similar to those of the corresponding chlorophylls [67]. The fluorescence spectrum of the chlorophylls is affected by solvents, with fluorescence being lost in pure and dry hydrocarbons [68]. It is also affected by temperature, molar concentration, and the degree of solvation [69]. 

The broad fluorescence spectrum of CDOM fills Fraunhofer lines presenting the possibility of using very sensitive remote and in situ sensors to study CDOM and chlorophyll in ocean waters (Stoertz et al., 1969 Gee et al., 1993 Vodacek et al., 1994 Hn and Voss, 1998). Although under some conditions has shown promise (i.e., Vodacek et al., 1994), Natural FDOM is very faint (f 1%) and the emission spectrum is to broad to be useful for passive remote sensing of organic matter. 

Chlorophyll itself shows a short-lived red fluorescence in solution. The green plants show a delayed fluorescence of approximately the same spectrum under specific conditions in which the electron transport chain is blocked. This delayed fluorescence results from the recombination of the charges (a process well known in electroluminescence), and its kinetics are complex and the decay quite long (several seconds). 

Similar to bacterial RC there is spectral and ESR evidence that a pheophytin a molecule operates as an intermediary electron acceptor in PSII-RC. Optical absorbance changes, with a spectrum similar to that of a pheophytin a anion radical could be detected in PSII-enriched particles illuminated at low redox potentials (— 0.65 V) [57,77]. The appearance of the Ph signal could be correlated to a decrease in the extent of the rise in fluorescence of PSII of chlorophyll a observed upon illumination [78]. This apparent discrepancy (reduction of an electron acceptor is expected to cause an increase of fluorescence) is now explained by the fact that the fluorescence increase is in reality a delayed fluorescence emitted by the return to the ground state of P -682 regenerated by electron transfer from the pheophytin anion [79]. The lifetime, of this transient fluorescence rise is 2-4 ns, and that of electron transfer from Ph to P -6%2 = 4 ns, when PSII particles are poised at —0.45 V [73]. This transient fluorescence increase is, however, almost totally suppressed when A,j,(Ph) is prereduced chemically before illumination. Using this experimental criterium the midpoint potential of the Ph /Ph couple has been estimated to be -0.61 V [73,80]. 

If a technique is to exploit differences in pigmentation, it needs prior measurements of the light-absorbing characteristics of the algae. Hence, the action spectrum for fluorescence of chlorophyll a is a tool for identifying the color types of algae (i). 

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