Seasonal changes in chlorophyll fluorescence quenching and the induction and capacity of the photoprotective xanthophyll cycle in Lobaria pulmonaria

2002 ◽  
Vol 80 (3) ◽  
pp. 255-261 ◽  
Author(s):  
Tyler DB MacKenzie ◽  
Marianna Król ◽  
Norman PA Huner ◽  
Douglas A Campbell
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Xanthophyll Cycle ◽  
Deciduous Forest ◽  
Light Exposure ◽  
Nonphotochemical Quenching ◽  
Pool Size ◽  
Lobaria Pulmonaria ◽  
Closed Canopy ◽  
Temperate Deciduous

Lobaria pulmonaria (L.) Hoffm. survives large changes in ambient light and temperature between winter and summer in temperate deciduous forests. Potential photosystem II (PSII) electron transport, measured at 20°C using chlorophyll fluorescence analysis, was consistent in thallus samples taken in March and August from a temperate deciduous forest, while the potential for nonphotochemical quenching (NPQ) was higher in March than in August. NPQ was, however, similar in March and August in a population from a coniferous site with a permanently closed canopy. Thalli measured at a typical March field temperature showed a depression of PSII electron transport, qp and gross CO2 uptake and a rise in realized NPQ. Xanthophyll cycle pigments were more abundant in the March than in the August samples in the deciduous forest populations but did not change significantly in the permanently closed-canopy population. In August, relatively low NPQ correlated with xanthophyll pool size in the deciduous forest samples. The more intense NPQ derived from low temperature and low CO2-electron demand in the March samples, however, was not correlated with xanthophyll pool size. Thus, most of the NPQ observed in the high light exposure March samples was not explained by variation in xanthophyll pool size.Key words: carotenoids, excitation quenching, lichen, nonphotochemical quenching, PSII electron transport.

The sun-exposed peel of apple fruit has a higher photosynthetic capacity than the shaded peel

2007 ◽  
Vol 34 (11) ◽  
pp. 1038 ◽  
Author(s):  
Li-Song Chen ◽  
Lailiang Cheng
Keyword(s):  
Chlorophyll Fluorescence ◽  
Electron Transport ◽  
Oxygen Evolution ◽  
Photosynthetic Capacity ◽  
Light Exposure ◽  
Calvin Cycle ◽  
Apple Fruit ◽  
Thermal Dissipation ◽  
The Sun ◽  
Significant Difference

To determine whether the sun-exposed peel of apple fruit has a higher photosynthetic capacity than the shaded peel, fruit peel samples were taken in both early July and early September from the exterior part of the canopy of mature ‘Liberty’/M.9 trees for measuring oxygen evolution, key enzymes and metabolites involved in photosynthesis, and chlorophyll fluorescence. Compared with the shaded peel, the sun-exposed peel had higher light-saturated oxygen evolution rate and higher light saturation point, but lower apparent and true quantum yields. The activity of ribulose-1,5-bisphosphate carboxylase/oxygenase, glyceraldehyde-3-phosphate dehydrogenase, phosphoribulokinase, stromal fructose-1,6-bisphosphatase, ADP-glucose pyrophosphorylase and sucrose-phosphate synthase (SPS) were higher in the sun-exposed peel than in the shaded peel on both sampling dates except that no significant difference was found in SPS activity between the two peel types in September. No significant difference was detected in the concentration of key metabolites (G6P, F6P, G1P, and PGA) between the sun-exposed peel and the shaded peel, suggesting that the response of the key enzymes to light exposure is well coordinated. Chlorophyll fluorescence quenching analysis showed that the sun-exposed peel had higher PSII quantum efficiency than the shaded peel at each given PFD, which resulted mainly from the higher photochemical quenching coefficient (qP). The sun-exposed peel had higher thermal dissipation capacity, as indicated by larger NPQ and Fo quenching, than the shaded peel at high PFD. In conclusion, the sun-exposed peel of apple fruit has higher activities of the Calvin cycle enzymes and higher rate of electron transport, leading to higher photosynthetic O2 evolution capacity. It appears that the acclimation of the Calvin cycle activities, thermal dissipation, and electron transport in apple peel are well coordinated in response to light exposure.

scholarly journals Can vegetation index track the interannual variation in gross primary production of temperate deciduous forests?

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Fan Liu ◽  
Chuankuan Wang ◽  
Xingchang Wang
Keyword(s):  
Primary Production ◽  
Vegetation Index ◽  
Near Infrared ◽  
Deciduous Forest ◽  
Gross Primary Production ◽  
Growing Season ◽  
Temperate Deciduous Forest ◽  
Near Infrared Reflectance ◽  
Modis Ndvi ◽  
Temperate Deciduous

Abstract Background Vegetation indices (VIs) by remote sensing are widely used as simple proxies of the gross primary production (GPP) of vegetation, but their performances in capturing the inter-annual variation (IAV) in GPP remain uncertain. Methods We evaluated the performances of various VIs in tracking the IAV in GPP estimated by eddy covariance in a temperate deciduous forest of Northeast China. The VIs assessed included the normalized difference vegetation index (NDVI), the enhanced vegetation index (EVI), and the near-infrared reflectance of vegetation (NIRv) obtained from tower-radiometers (broadband) and the Moderate Resolution Imaging Spectroradiometer (MODIS), respectively. Results We found that 25%–35% amplitude of the broadband EVI tracked the start of growing season derived by GPP (R2: 0.56–0.60, bias < 4 d), while 45% (or 50%) amplitudes of broadband (or MODIS) NDVI represented the end of growing season estimated by GPP (R2: 0.58–0.67, bias < 3 d). However, all the VIs failed to characterize the summer peaks of GPP. The growing-season integrals but not averaged values of the broadband NDVI, MODIS NIRv and EVI were robust surrogates of the IAV in GPP (R2: 0.40–0.67). Conclusion These findings illustrate that specific VIs are effective only to capture the GPP phenology but not the GPP peak, while the integral VIs have the potential to mirror the IAV in GPP.

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