The Response of Xanthophyll Cycle-dependent Energy Dissipation in Alocasia brisbanensis to Sunflecks in a Subtropical Rainforest

1997 ◽  
Vol 24 (1) ◽  
pp. 27 ◽  
Author(s):  
David H. Barker ◽  
Barry A. Logan ◽  
William W. Adams III ◽  
Barbara Demmig-Adams
Keyword(s):  
Chlorophyll Fluorescence ◽  
Energy Dissipation ◽  
Xanthophyll Cycle ◽  
Thylakoid Membrane ◽  
Proton Gradient ◽  
Light Activation ◽  
Understory Plants ◽  
Photooxidative Damage ◽  
Photosynthetic Responses ◽  
Cycle Dependent

The photosynthetic responses of leaves of Alocasia brisbanensis (F.M. Bailey) Domin (Araceae) to sunflecks were monitored via chlorophyll fluorescence beneath the canopy of a subtropical rainforest in Australia. Additionally, the size and conversion state of the xanthophyll cycle were determined. Acclimation to understory environments that regularly experienced sunflecks involved small increases in the size of the xanthophyll cycle pool in comparison to understory plants that never received sunflecks. In understory plants that regularly experienced sunflecks the rate of photochemistry and the level of xanthophyll cycle-dependent energy dissipation closely tracked changes in incident PFD. Subsequent to the first sunfleck plants tended to retain their pool of xanthophyll cycle carotenoids as the deepoxidised forms (antheraxanthin and zeaxanthin) throughout the day. Retention of these deepoxidised forms apparently allows the trans-thylakoid membrane proton gradient to engage and disengage dissipation rapidly in response to a sunfleck, thereby mitigating photooxidative damage and ensuring a rapid return to efficient light utilisation via photosynthesis in limiting light. Our results were also in agreement with previous studies that demonstrated a requirement for light activation of photosynthesis.

Photochemistry and xanthophyll cycle-dependent energy dissipation in differently oriented cladodes of Opuntia stricta during the winter

1998 ◽  
Vol 25 (1) ◽  
pp. 95 ◽  
Author(s):  
David H. Barker ◽  
Barry A. Logan ◽  
William W. Adams III ◽  
Barbara Demmig-Adams
Keyword(s):  
Energy Dissipation ◽  
Excitation Energy ◽  
Xanthophyll Cycle ◽  
Photosynthetic Apparatus ◽  
High Rate ◽  
Psii Efficiency ◽  
Thermal Energy Dissipation ◽  
Dramatic Decline ◽  
Absorption Of Light ◽  
Cycle Dependent

The photosynthetic and energy dissipation responses of four differently oriented photosynthetic surfaces (cladodes) from the cactus Opuntia stricta (Haw.) Haw. were studied in the field during the winter in Australia. Even under very low PFD (i.e. -2 s-1) all surfaces experienced a dramatic decline in photosystem II (PSII) efficiency during the morning period when temperatures were below freezing. However, light energy absorbed during the warmer afternoon period was more efficiently utilised for photochemistry with less diversion through the thermal energy dissipation pathway. Low temperature presumably reduced the proportion of excitation energy that could be utilised photosynthetically, resulting in a high rate of energy dissipation with a concomitant decline in PSII efficiency. A lag in the diurnal de-acidification of malic acid, and therefore the availability of endogenous CO2, may have also contributed to the low rate of photochemistry during the morning period. We interpret the increase in energy dissipation and decline in PSII efficiency as a controlled response of PSII that is dependent upon the de-epoxidised components of the xanthophyll cycle under conditions when the absorption of light exceeds the capacity of the photosynthetic apparatus to process the excitation energy through photochemistry.

'Photoinhibition' During Winter Stress: Involvement of Sustained Xanthophyll Cycle-Dependent Energy Dissipation

1995 ◽  
Vol 22 (2) ◽  
pp. 261 ◽  
Author(s):  
WW Iii Adams ◽  
B Demmig-Adams ◽  
AS Verhoeven ◽  
DH Barker
Keyword(s):  
Energy Dissipation ◽  
Xanthophyll Cycle ◽  
Quantitative Relationship ◽  
Climatic Conditions ◽  
Dissipation Process ◽  
Photosystem Ii Efficiency ◽  
Wide Range ◽  
Chilling Temperatures ◽  
Cycle Dependent ◽  
Daily Changes

Sustained decreases in intrinsic photosystem II efficiency (i.e. Fv/Fm) in response to high light and chilling temperatures were examined in eight species, and were found to be accompanied by the retention of zeaxanthin (Z) and antheraxanthin (A) overnight. The quantitative relationship between changes in Fv/Fm and the A + Z level during these sustained changes on cold days was similar to that obtained for rapidly reversible changes on warm days. Furthermore, upon removal of leaves from the field, recovery from 'photoinhibition' (the reversal of the depression of Fv/Fm) matched the timecourse of the epoxidation of Z and A to violaxanthin (V). These findings suggest that the 'photoinhibition' occuring in these species might be due to the sustained engagement of these de-epoxidised components of the xanthophyll cycle in photoprotective energy dissipation. When examined over the course of several days during the winter, the predawn conversion state of the xanthophyll cycle responded to the daily changes in minimum air (and leaf) temperature, such that the xanthophyll cycle was largely de-epoxidised prior to sunrise on cold nights and was present predominantly as V after nights when the nocturnal temperatures were above freezing. In addition, in some of the species examined, there was a large acclimation of the xanthophyll cycle pool size to the level of excessive light, with a much larger pool present in the leaves examined during the winter and that pool being de-epoxidised to Z and A to a much greater degree at midday than from similar leaves examined during the summer. The xanthophyll cycle, and the photoprotective energy dissipation process associated with it, would thus appear to provide plants the flexibility required to deal with the excessive levels of light absorbed by chlorophyll under a wide range of climatic conditions, and can quite possibly account for the 'photoinhibition' observed during winter stress.

Xanthophyll Cycle-Dependent Energy Dissipation and Flexible Photosystem II Efficiency in Plants Acclimated to Light Stress

1995 ◽  
Vol 22 (2) ◽  
pp. 249 ◽  
Author(s):  
B Demmig-Adams ◽  
WW Iii Adams ◽  
BA Logan ◽  
AS Verhoeven
Keyword(s):  
Energy Dissipation ◽  
Photosystem Ii ◽  
Xanthophyll Cycle ◽  
Light Stress ◽  
Photon Flux ◽  
Growth Environment ◽  
Psii Efficiency ◽  
Cycle Dependent ◽  
Shade Leaves ◽  
Sun Leaves

The effect of an acclimation to light stress during the growth of leaves on their response to high photon flux densities (PFDs) was characterised by quantifying changes in photosystem II (PSII) characteristics and carotenoid composition. During brief experimental exposures to high PFDs sun leaves exhibited: (a) much higher levels of antheraxanthin + zeaxanthin than shade leaves, (b) a greater extent of energy dissipation in the light-harvesting antennae, and (c) a greater decrease of intrinsic PSII efficiency that was rapidly reversible. During longer experimental exposures to high PFD, deep-shade leaves but not the sun leaves showed slowly developing secondary decreases in intrinsic PSII efficiency. Recovery of these secondary responses was also slow and inhibited by lincomycin, an inhibitor of chloroplast-encoded protein synthesis. In contrast, under field conditions all changes in intrinsic PSII efficiency in open sun-exposed habitats as well as understory sites with intense sunflecks appeared to be caused by xanthophyll cycle-dependent energy dissipation. Furthermore, comparison of leaves with different maximal rates of electron transport revealed that all leaves compensated fully for these differences by dissipating very different amounts of absorbed light via xanthophyll cycle-dependent energy dissipation, thereby all maintaining a similarly low PSII reduction state. It is our conclusion that an increased capacity for xanthophyll cycle-dependent energy dissipation is a key component of the acclimation of leaves to a variety of different forms of light stress, and that the response of leaves to excess light experienced in the growth environment is thus likely to be qualitatively different from that to sudden experimental exposures to PFDs exceeding the growth PFD.

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