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2. Role of thermal dissipation in the photoprotection in cucumber plants after exposure to a chill stress

Creator:
Zhou, Y. H., Mao, W. H., Zhang, Y. Y., Huang, L. F., Hu, W. H., and Yu, J. Q.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
alternative elctron sink, chilling, Cucumis sativus, photosynthesis, and photosystem 2
Language:
Multiple languages
Description:
Experiments were carried out to investigate the changes in CO2 assimilation, photon allocation, and photosynthetic electron flux in leaves of cucumber (Cucumis sativus L.) plants after chilling stress. Chilling significantly decreased CO2 assimilation, the energy flux via linear electron transport (J PS2) and non-constitutive thermal dissipation (J NPQ) but increased fluorescence and constitutive thermal dissipation (J f,D) in chilling-sensitive genotype Jinyan No. 4. In contrast, chilling had little effects on J NPQ and J f,D although CO2 assimilation and J PS2 were inhibited in chilling-tolerant genotype Jinchun No. 3. In parallel with the reduction in J PS2, electron flux to oxygenation and carboxylation by ribulose-1,5-bisphosphate carboxylase/oxygenase all significantly decreased while electron flux to O2 significantly increased, especially in chilling-sensitive genotype. Thermal and fluorescence dissipation were the main energy dissipation pathways whilst water-water cycle was an important electron sink when photosynthetic carbon reduction was suppressed after chilling. Chilling sensitivity of the photosynthetic apparatus was related to the operation of different photoprotection mechanisms. and Z. H. Zhou ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Seasonal photosynthetic changes in the green-stemmed Mediterranean shrub Calicotome villosa: a comparison with leaves

Creator:
Yiotis, C., Psaras, G. K., and Manetas, Y.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
carotenoids, chlorophyll, drought stress, electron transport rates, photoinhibition, photosystem 2 efficiency, and spiny broom
Language:
Multiple languages
Description:
Some photosynthetic attributes of leaves and stems were seasonally followed in the small-leaved, summer-deciduous, green-stemmed Mediterranean shrub Calicotome villosa. Both leaves and stems displayed similar photon energy-saturated photosystem 2 (PS2) efficiencies with a minimum during winter. A second minimum in stems during the leafless summer period could be ascribed to sustained photoinhibition. Yet, stems were slightly inferior in photon capture, resulting partly from lower chlorophyll (Chl) contents and partly from higher reflectance due to pubescence. As a result, photon energy-saturated linear electron transport rates were slightly higher in leaves. However, when the total leaf and stem areas were taken into account, this superiority was abolished during autumn and winter and more than overturned during spring. Given that during summer the stems were the only photosynthetic organs, the yearly photosynthetic contribution of stems was much higher. Chl contents in stems displayed a transient and considerable summer drop, accompanied by an increase in the carotenoid to Chl ratio, indicating a photo-protective adaptation to summer drought through a decrease of photo-selective capacity, typical for leaves of many Mediterranean plants. and C. Yiotis, G. K. Psaras, Y. Manetas.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public