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2. Photosynthetic response of poikilochlorophyllous desiccation-tolerant Pleurostima purpurea (Velloziaceae) to dehydration and rehydration

Creator:
Aidar, S. T., Meirelles, S. T., Oliveira, R. F., Chaves, A. R. M., and Fernandes-Júnior, P. I.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
fotosyntéza, photosynthesis, chlorophyll fluorescence, gas exchange, photoprotective mechanisms, vegetative desiccation tolerance, Pleurostima purpurea, 2, and 581
Language:
Multiple languages
Description:
The poikilochorophyllous, desiccation-tolerant (PDT) angiosperm, Pleurostima purpurea, normally occurs in less exposed rock faces and slightly shady sites. Our aim was to evaluate the light susceptibility of the photosynthetic apparatus during dehydration-rehydration cycle in P. purpurea. In a controlled environment, the potted plants were subjected to water deficit under two different photosynthetic photon flux densities [PPFD, 100 and 400 μmol(photon) m-2 s-1]. In the higher PPFD, net photosynthetic rate (PN) become undetectable after stomata closure but photochemical efficiency of photosystem II, electron transport rate, and photochemical quenching coefficient were maintained relatively high, despite a partial decrease. The photochemical activity was inhibited only after the complete loss of chlorophylls, when leaf relative water content dropped below 72% and total carotenoids reached maximal accumulation. Nonphotochemical energy dissipation increased earlier in response to dehydration under higher PPFD. PN and photochemical activity were fully recovered after rehydration under both light treatments. Our results suggested that the natural occurrence of P. purpurea should not be restricted by the light intensity during the complete desiccation-rehydration cycles., S. T. Aidar, S.T. Meirelles, R. F. Oliveira, A. R. M. Chaves, P. I. Fernandes-Júnior., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Sap flow index as an indicator of water storage use

Creator:
Nadezhdina, Nadezhda, Čermák, Jan, Downey, Alec, Nadezhdin, Valeriy, Perämäki, Martti, David, Jorge Soares, Pinto, Clara A., and David, Teresa Soares
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
diameter fluctuation, heat field deformation, multi-point sensor, symmetrical temperature difference, radial and circumferential variations, sap flow measurement, tree, and transpiration
Language:
Slovak
Description:
Symmetrical temperature difference also known as the sap flow index (SFI) forms the basis of the Heat Field Deformation sap flow measurement and is simultaneously collected whilst measuring the sap flow. SFI can also be measured by any sap flow method applying internal continuous heating through the additional installation of an axial differential thermocouple equidistantly around a heater. In earlier research on apple trees SFI was found to be an informative parameter for tree physiological studies, namely for assessing the contribution of stem water storage to daily transpiration. The studies presented in this work are based on the comparative monitoring of SFI and diameter in stems of different species (Pseudotsuga menziesii, Picea omorika, Pinus sylvestris) and tree sizes. The ability of SFI to follow the patterns of daily stem water storage use was empirically confirmed by our data. Additionally, as the HFD multipointsensors can measure sap flow at several stem sapwood depths, their use allowed to analyze the use of stored water in different xylem layers through SFI records. Radial and circumferential monitoring of SFI on large cork oak trees provided insight into the relative magnitude and timing of the contribution of water stored in different sapwood layers or stem sectors to transpiration.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public