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Light climate and PP in the Arctic > Bio-optics > Flashcards

Bio-optics Flashcards

1
Q

What is the premise for bio-otpics measurements?

A

All methods in this report are based on the fact that light is absorbed by pigments in algal tissue.

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2
Q

Are enzyme involve in the light reactions in photosynthesis (PSII related)?

A

No,it is therefore relatively temperature stable

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3
Q

What is the role of photosynthetic pigments?

A

The role of photosynthetic pigments (PSP’s) in the cells is to catch photons and channel them to the reaction centres.

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4
Q

Describe briefly the spectral absorption of the 3 major pigments group.

A

The most common pigment, chlorophyll a, absorbs light in the blue and red wavebands, while not in the green. Other pigments like the carotenoid fucoxanthin absorb further into the blue-green spectrum, while phycobiliproteins such as phycoerythrin absorb light in the green and orange wavebands

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5
Q

how do you calculate [chla] in vitro?

A

With OD ( the optical density) measured as [absorption] at 665nm and 750nm, VE is the extraction volume in [ml], EQ is the extinction coefficient of the extraction medium (74.5 L g-1 cm-1 for methanol at 665nm) and VF is the filtration volume in [L].

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6
Q

What is the SpectraPen?

A

The SpectraPen (model SN-SP-245 from Photon Systems Instruments) is a handheld spectroradiometer that has a cosine corrector, which collects light from a 180° angle. It has a spectral range from 340-780nm

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7
Q

What is rETR and how is it calculate?

A

the relative electron transport rate (rETR) was calculated using the formula: rETR = EPAR * Fv/Fm. rETR describes the effectiveness of electron transfer rate (photosynthesis-rate) at a given irradiance.

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8
Q

How does the cell cope with irradiance higher than what the reaction centres can handle?

A

To cope with this, photosynthetically active cells have evolved ways to reduce the energy of the photon, giving it off as light (fluorescence, F) or as heat (either non-photochemical regulated temperature quenching, NPQ (active heat dissipation), or non-photochemical non-regulated temperature quenching, NO (passive heat dissipation)).

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9
Q

What is F (PAM) or F’(FRRf)?

A

F0 (dark) or F0’ (actinic light) = Fluorescence yield measured briefly before onset of saturation pulse

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10
Q

What is Fm’?

A

Fluorescence yield reached during last saturation pulse in actinic light. Fm denotes dark acclimated cells

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11
Q

What is PAR (PAM) or E( FRRf)?

A

EPAR

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12
Q

What is the yield (PAM) or Fq’/Fm’ (FRRf)?

A

Fv’/Fm’ = Effective quantum yield of PSII fluorescence

in dark = maximum; Fv/Fm

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13
Q

What is ETR (PAM) or rP (FRRf)?

A

Relative electron transport rate

rETR = yield * EPAR

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14
Q

What is sigma?

A

Absorption cross-section of PSII light harvesting antenna (i.e., the energy delivery)

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15
Q

What is Tau?

A 
The rate of reopening of PSII
reaction centres (= turnover time of reaction centres)
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16
Q

What is the transmitted light?

A

The percentage of transmitted light, which equals the amount of light that is left after absorption by the macroalgae tissue

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17
Q

What is the relationship between absorption and reflectance?

A

They are inverse

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18
Q

Name one of the weakness of Ek.

A

Ek only gives an instant view of photo-acclimation

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19
Q

What happen to the pigments properties in vitro?

A

pigment properties change when extracted from the thylakoids. From the absorption spectra it is evident that the major red-light peaks of Chl a (S. latissima: 676 nm, Ulvaria sp.: 679 nm and P. palmata: 678 nm) are shifted towards lower wavelengths (664 nm for all species) when extracted in vitro. These peaks retain the same signal intensity relative to their curve.

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20
Q

Why do pigment properties change when extracted?

A

This general response should be interpreted as a result of extracted pigments now being free in solution, and not bound to the proteins of reaction centres or antennas. The optical properties of Chl a and Chl b differ significantly. In the same way, pigment absorption heterogeneity occurs between species, but is cancelled out when free in solution, simply because extracted Chl a (and the rest of the pigments) are detached from the apo-proteins, in addition to solvent effects.

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21
Q

What is particular to phycoerythrin?

A

These water soluble pigments make up the majority of the phycobilisomes attached to PSII in P. palmata. Since the phycobilisomes only associate with PSII, their absorption spectrum was subtracted from the in vivo total absorption.

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22
Q

What is a obvious feature of reflectance?

A

An obvious feature of reflectance is that maximum reflectance should correspond to the apparent colour of the macroalgae

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23
Q

What does the transmittance represent?

A

Transmittance measurement of macroalgae tissue is an efficient way for looking at the general pigment composition and the relative contribution of different pigments to absorption of light. It is important to keep in mind that the transmittance spectrum is the result of the absorption of all pigments in the macroalgae tissue.

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24
Q

Where are the red algae growing and how does it effect their transmittance?

A

The results indicate that the red algae are slightly more efficient in absorbing light in the EPAR than the brown algae. This corresponds to the ecological habitat of the red algae, where they are growing often in the shade of the brown kelp species

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25
Q

What factor could have infuenced the transmittance of the algal tissus?

A

the thickness or health of the tissue

26
Q

What can explain the difference between the PAM and the FRRf measurements (in the temperature experiment)?

A

This could be explained by a variety of factors. First of all, the diving-PAM and FRRf give data for similar parameters, but the underlying method is slightly different: the diving-PAM is a multiple turnover system and the FRRf a single turnover system. These cannot be directly compared (Prasil 2018). Second, we have to keep in mind that we did not use replicates for the diving-PAM and FRRf. The variation between individuals of the same species, and even of different tissues within one specimen could be large. Third, the “cold temperature” and “room temperature” treatments differed between the diving-PAM and FRRf. Especially the room temperature, which was 15-17°C in the diving-PAM and 24°C in the FRRf, could induce a different response. In addition, the diving-PAM setup was not completely dark.

27
Q

What are the proes and cons of using the FRRf?

A

In general, the environment is easier to control in the FRRf, due to the temperature control and the completely dark environment in which the cuvette is placed. However, the FRRf is not build for macroalgae and correct placement of macroalgae in cuvette is difficult. The saturation pulse comes from underneath the cuvette, in such a way that the macroalgal tissue should ideally be placed horizontally, and the actinic light comes from the sides of the cuvette, in such a way that the tissue should ideally be placed vertically in the cuvette. We solved this by bending the tissue so that it is both on a vertical and horizontal plane within the cuvette (Figure 17). However, the actinic light does not shine on the exact same piece of the tissue that is measured with the saturation pulse. The measurements are therefore not completely accurate. In addition, once the cuvette is placed in the FRRf, the tissue is no longer visible and the tissue could change its position within the cuvette without us noticing

28
Q

What are the proes and cons of the diving-PAM?

A

. With the diving-PAM on the other hand, we have full control of the setup and the position of the macroalgal tissue, measuring light and actinic light. The diving-PAM however must be handled manually and only works for macroalgae. This makes it good for field work but is prone to human error and inconsistencies during a lab setup.

29
Q

What are the major photosynthetic and photoprotective pigments in the Chlorophyta (green algae)?

A
  • Chl a, Chl b

- Xanthophylls (lutein, violaxanthin, neoxanthin, antheraxanthin, zeaxanthin), Carotenes (β-carotene)

30
Q

What are the major photosynthetic and photoprotective pigments in the Rhodophyta – Red algae?

A
  • Chl a, phycobiliproteins (e.g. phycocyanin, phycoerytrhin)

- Xanthophylls (zeaxanthin, some species also violaxanthin and antherexanthin)

31
Q

What are the major photosynthetic and photoprotective pigments in the Phaeophyceae – Brown algae?

A
  • Chl a, Chl c, Xantophylls (fucoxanthin)

- Xantophylls (violaxanthin, antheraxanthin, zeaxanthin), Carotenes (β-carotene),

32
Q

What are the major photosynthetic and photoprotective pigments in the Bacillariophyceae – Diatoms?

A
  • Chl a, Chl c, Xanthophylls (fucoxanthin)

- Carotenes (β-carotene), Xanthophylls (diatoxanthin, diadinoxanthin

33
Q

What are the major photosynthetic and photoprotective pigments in the Cryptophyta – Cryptomonadss?

A
  • Chl a, Chl c2, phycobiliproteins (only phycocyanin and phycoerytrhin)
  • Carotenes (α-carotene), Xanthophylls (alloxanthin, zeaxanthin)
34
Q

What are the major photosynthetic and photoprotective pigments in the Cyanophyta – Cyanobacteria?

A
  • Chl a, phycobiliproteins (e.g. phycocyanin, phycoerytrhin

- Xanthophylls (e.g. zeaxanthin)

35
Q

What does F means?

A

Fluorescence. Emission of a photon by an electron going from a higher energy state to a lower.

36
Q

What does kP means?

A

Photochemistry. The energy from incoming light going to photochemistry.

37
Q

What does kD means?

A

Non-regulated heat dissipation (basal heat dissipation). The energy from incoming light going to non-regulated heat dissipation.

38
Q

What does kF means?

A

Fluorescence emission. The energy of incoming light going to fluorescence.

39
Q

What does kNPQ means?

A

Light induced regulated heat dissipation, or non-photochemical quenching. The energy from incoming light going to regulated heat dissipation.

40
Q

What does φPSII means?

A

The fraction of energy from incoming light going to photochemistry. Also known as quantum yield.

41
Q

What does φNO means?

A

The fraction of energy from incoming light going to fluorescence and non-regulated heat dissipation.

42
Q

What does φNPQmeans?

A

The fraction of energy from incoming light going to non-photochemical quenching.

43
Q

What does F0 means?

A

Auto-fluorescence. The basic fluorescent yield in darkness. Should be ≈0.

44
Q

What does Fm means?

A

The maximum fluorescent yield after a saturation pulse in dark acclimated cells.

45
Q

What does Fv means?

A

The effective fluorescent yield measured as Fm-F0.

46
Q

What does Fv/Fm means?

A

Maximum quantum yield in dark acclimated cells.

47
Q

What does ‘ means?

A

In actinic light

48
Q

What does σ means?

A

Sigma. Effective absorption cross section of PSII light harvesting antenna measured in [nm-2]. An estimate of energy delivery effectiveness. The higher the value the more energy delivered and the more effective system.

49
Q

What does τ means?

A

Tau. Turnover time of PSII. How fast PSII is oxidized (reopened) after it’s reduced (closed). Measured in [ms]. The higher the value, the faster PSII opens and closes and the more effective the system.

50
Q

What is the PE curve?

A

Photosynthesis vs. irradiance curve. Shows how photosynthesis responds to increasing light intensities as a saturation curve with EPAR on the x-axis and rETR on the y-axis.

51
Q

What is rETR?

A

Relative electron transport rate. A measure of the “speed” (effectiveness) of photosynthesis given as yield*irradiance. The higher the rETR the faster the electron transport and therefore higher photosynthesis.

52
Q

What is Pmax?

A

The maximum photosynthetic rate given as the maximum rETR.

53
Q

What is α?

A

The maximum slope of the P/E-curve. Is a value for the irradiance where photosynthetic effectiveness increases at the fastest rate.

54
Q

What is Ek?

A

Photosynthetic saturation coefficient. The crossing between α and Pmax on a P/E-curve. Is given as the irradiance level where photosynthesis is optimum and crossing over from being undersaturated to becoming saturated.

55
Q

What is the optical density?

A

OD or Absorbance (dimensionless)

56
Q

What is absorption?

A

(OD ()*2.3)/optical pathlength (of e.g. cuvette or tissue)

57
Q

What is the reflectance?

A

The amount of reflectance of light [%] from a sample in relation to reflection standard (flat spectrum from 400-700 nm).

58
Q

What is the transmittance?

A

The amount of light transmitted through something measured in [%].

59
Q

What is a spectrometer?

A

Lab equipment used for light measurement investigations such as absorption and reflectance. Uses external light source and is often more precise than a spectroradiometer.

60
Q

What is a Spectroradiometer?

A

Complete spectrometer setup in a hand-held version that can be used in the field and is cosine corrected to 180° degrees of incoming light.

61
Q

What is a single turnover?

A

of PSII. A single turnover is a single open-and-close event of PSII by induction of a fast, high-energy flash. Used in FRRf-measurements.

62
Q

What is a multiple turnover?

A

of PSII. Multiple open-and-close events of PSII by induction of a rather slow, high energy flash. Used in diving-PAM measurements.

Light climate and PP in the Arctic (5 decks)

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