Oxygen per flash from leaf disks quantifies Photosystem II

Chow, Wah Soon; Hope, AB; Anderson, Jan M.

doi:10.1016/s0005-2728(89)80408-6

Cited by 92 publications

(69 citation statements)

References 21 publications

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“…1). The value f, conveniently measured by Chl a fluorescence, is directly proportional to the average yield of oxygen per single-turnover, repetitive flash in Capsicum leaves (16,25); in turn, the average yield of oxygen per flash represents the number of functional PSII centers in a range of plant species tested (35). Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Plants of C. annuum L. were grown in a potting mixture supplemented by a slow-release fertilizer and watered daily. The growth chamber was maintained at a 24°C͞21°C (day͞night) regime, the irradiance during the 12-h photoperiod being 250 mol of photons per m 2 per s. Fully expanded leaves were taken from plants at [35][36][37][38][39][40][41][42][43][44][45] (23,24), which is directly proportional to the oxygen yield per single-turnover saturating flash in C. annuum (25). The functional fraction of PSII ( f ) was calculated as the ratio of 1͞F o Ϫ 1͞F m for a treated leaf to that for a control, nonilluminated leaf.…”

Section: Methodsmentioning

confidence: 99%

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Populations of photoinactivated photosystem II reaction centers characterized by chlorophyllafluorescence lifetimein vivo

Matsubara

Chow

2004

Proc. Natl. Acad. Sci. U.S.A.

124

111

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O xygenic photosynthetic organisms grow under an everchanging sunlight environment. Fluctuations of solar energy input can be accommodated by a tradeoff between energy utilization in photosynthetic carbon assimilation and energy dissipation by various photoprotective mechanisms that modulate absorption and dissipation of excess light energy (1-3). Despite the complex suite of strategies for photoprotection, however, photooxidative damage inevitably occurs to photosystem (PS) II, in which P680 ϩ (a special Chl in the PSII reaction center), the strongest biological oxidant, is generated to split water to molecular oxygen, protons, and electrons (4). The consequent loss of PSII photochemical efficiency measured under low light, termed photoinhibition or photoinactivation (5), depends inter alia on the number of absorbed photons during the light exposure (6-8). That is, PSII photoinactivation can occur with a light-dosage-dependent probability under any light environment in nature, ranging from limiting to saturating irradiances. Over a sunny day, the entire population of PSII in a leaf may undergo photoinactivation.Yet, effects of photoinactivation on PSII efficiency are not always obvious; they are noticeable only when the rate of inactivation exceeds the capacity for rapid and efficient repair of nonfunctional PSII reaction centers by de novo synthesis of D1 protein (psbA gene product in PSII reaction center) (9). The operation of the PSII repair cycle involves coordinated regulation of degradation and synthesis of D1 protein (10). When the supply of newly synthesized D1 protein is insufficient, such as under high light and͞or low temperature, the degradation process also slows down (11,12), resulting in the accumulation of nonfunctional PSII reaction centers in stacked grana domains of the thylakoid membranes of higher plants (13). These nonfunctional PSII centers, capable of light absorption but not of photosynthetic electron transfer, reduce the PSII quantum efficiency of leaves or leaf segments.An important implication of PSII photoinactivation is that nonfunctional PSII centers, still embracing pigment molecules, can exacerbate photooxidative damage to the thylakoid membranes unless light energy absorbed by the pigments is dissipated safely. Thus, it has been hypothesized that photoinactivated PSII complexes are able to efficiently dissipate excitation energy harmlessly (14), and further, may contribute to photoprotection of their functional neighbors by acting as sinks for excitation energy (13,15).Experimental results consistent with this hypothesis have emerged from recent studies using leaves of Capsicum annuum L (16, 17). In leaves of C. annuum in the presence of lincomycin (an inhibitor of chloroplast-encoded protein synthesis), the functional fraction of PSII ( f ), determined from the oxygen yield per single-turnover flash or from chlorophyll (Chl) a fluorescence, decreased monoexponentially from 1.0 (ϭ the original level) to Ϸ0.3 under illumination (16). However, the decrease in f thereafter proceed...

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Populations of photoinactivated photosystem II reaction centers characterized by chlorophyllafluorescence lifetimein vivo

Matsubara

Chow

2004

Proc. Natl. Acad. Sci. U.S.A.

124

111

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“…3). 02 flash yield has been used to measure the relative number of active PSII centers in algae ( 11) and more recently in leaf discs (7,18). It should be pointed out that even before high PFD exposure, resistant leaf discs had a lower 02 flash yield (15), probably due to incomplete recovery between flashes of some PSII centers (18).…”

Section: High Pfd-induced Decrease In Photosynthetic Efficiencymentioning

confidence: 99%

High Light-Induced Reduction and Low Light-Enhanced Recovery of Photon Yield in Triazine-Resistant Brassica napus L

Hart¹,

Stemler²

1990

Plant Physiol.

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Triazine-resistant and -susceptible Brassica napus L. plants grown under low photon flux density (PFD) have previously been shown to exhibit a similar photon yield. In contrast, high PFDgrown resistant plants have a lower photon yield than high PFD- This work was initiated to test the hypothesis that high PFD light causes the differential reduction in photon yield observed in resistant plants. We exposed low PFD-grown B. napus leaf discs to high PFD and measured photon yield and other photosynthetic traits. We found that exposure to high PFD induces a differential decrease in photon yield in resistant plants. We also observed that the characteristics of recovery from decreased photon yield are consistent with the hypothesis that resistant plants are more sensitive to photoinhibition of PSII than susceptible plants. MATERIALS AND METHODSThe development of triazine resistance in crop plants is an attractive goal because of the potential benefits it offers for weed control.

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“…Flashing light was supplemented with far red light supplied by a Sylvania 120W EKN Tungsten Halogen projector lamp fitted with a Schott RG-9 filter and directed to the leaf disk with a fiber optic light guide. Far red light was applied to keep PSI centers open to prevent their limiting noncyclic electron flow (7). Exposure of leafdiscs to far red light alone produced no detectable 02 evolution.…”

Section: Oxygen Flash Yieldmentioning

confidence: 99%

Similar Photosynthetic Performance in Low Light-Grown Isonuclear Triazine-Resistant and -Susceptible Brassica napus L

Hart¹,

Stemler²

1990

Plant Physiol.

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Oxygen per flash from leaf disks quantifies Photosystem II

Cited by 92 publications

References 21 publications

Populations of photoinactivated photosystem II reaction centers characterized by chlorophyllafluorescence lifetimein vivo

Populations of photoinactivated photosystem II reaction centers characterized by chlorophyllafluorescence lifetimein vivo

High Light-Induced Reduction and Low Light-Enhanced Recovery of Photon Yield in Triazine-Resistant Brassica napus L

Similar Photosynthetic Performance in Low Light-Grown Isonuclear Triazine-Resistant and -Susceptible Brassica napus L

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