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21.
Goltsev V Zaharieva I Chernev P Kouzmanova M Kalaji HM Yordanov I Krasteva V Alexandrov V Stefanov D Allakhverdiev SI Strasser RJ 《Biochimica et biophysica acta》2012,1817(8):1490-1498
Water deficit is one of the most important environmental factors limiting sustainable crop yields and it requires a reliable tool for fast and precise quantification. In this work we use simultaneously recorded signals of photoinduced prompt fluorescence (PF) and delayed fluorescence (DF) as well as modulated reflection (MR) of light at 820nm for analysis of the changes in the photosynthetic activity in detached bean leaves during drying. Depending on the severity of the water deficit we identify different changes in the primary photosynthetic processes. When the relative water content (RWC) is decreased to 60% there is a parallel decrease in the ratio between the rate of excitation trapping in the Photosystem (PS) II reaction center and the rate of reoxidation of reduced PSII acceptors. A further decrease of RWC to 20% suppresses the electron transfer from the reduced plastoquinone pool to the PSI reaction center. At RWC below values 15%, the reoxidation of the photoreduced primary quinone acceptor of PSII, Q(A)(-), is inhibited and at less than 5%, the primary photochemical reactions in PSI and II are inactivated. Using the collected sets of PF, DF and MR signals, we construct and train an artificial neural network, capable of recognizing the RWC in a series of "unknown" samples with a correlation between calculated and gravimetrically determined RWC values of about R(2)≈0.98. Our results demonstrate that this is a reliable method for determination of RWC in detached leaves and after further development it could be used for quantifying of drought stress of crop plants in situ. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial. 相似文献
22.
Detelin Stefanov Elisaveta Stoimenova Galina Marinova Bistra Ivanova Aglika Edreva 《Acta Physiologiae Plantarum》2012,34(1):181-190
Altered photosynthetic reactions in cucumber mosaic virus (CMV) inoculated leaves of virus resistant lines L113 and L57 and
susceptible pepper (Capsicum annuum L.) plants cv. Albena grown in controlled environment and in the field were investigated. The CMV inoculated leaves of virus
resistant lines developed different symptoms—necrotic local lesions on L113 and chlorotic spots on L57 while the same leaves
of susceptible cv. Albena were symptomless. The changes in Photosystem II (PSII) and PSI electron transport were evaluated
by chlorophyll fluorescence, and far-red (FR) light induced leaf absorbance A
810–860. CMV infection caused a decrease in maximal PSII quantum yield, F
v/F
m, in susceptible leaves. Increased non-photochemical fluorescence quenching in CMV-inoculated leaves of both resistant lines
were observed. In CMV-inoculated leaves of all tested plants FR light induced P700 oxidation was decreased. In the present
study, the viral-infected pepper plants grown in controlled environment to avoid the effects of abiotic factors were used
as model system that allow us to investigate the differences in leaf senescence in CMV-inoculated leaves of susceptible and
resistant pepper lines expressing different symptoms. Earlier leaf falls of inoculated leaves as a result of accelerated leaf
senescence is important for building successful secondary virus resistance strategy following fast responses such as hypersensitive
reaction. 相似文献
23.
Chemical composition of the sponge Chondrosia reniformis from [2pt] the Canary Islands 总被引:1,自引:1,他引:0
Jordan Nechev William W. Christie Rafael Robaina Fernando M. de Diego Albena Ivanova Simeon Popov Kamen Stefanov 《Hydrobiologia》2002,467(1-3):91-98
Lake Zempoala was studied throughout 16 months in 1996–1997. It is a shallow monomictic lake situated at 2800 masl at the Neovolcanic Belt, well within the Mexican tropical zone. Most of the phytoplankton species in this lake may be characterized as temperate, according to their geographical distribution. A break down in phytoplankton biomass was observed before the lake's circulation, and open to question if a clear-water phase could be present in a tropical lake. 相似文献
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K. Georgieva A. Ivanova S. Doncheva S. Petkova D. Stefanov E. Péli Z. Tuba 《Biologia Plantarum》2011,55(3):581-585
Desiccation of Xerophyta scabrida caused considerable damage of chloroplast ultrastructure together with a complete loss of chlorophyll. Upon rehydration,
the relative water content of the pale-green leaves almost reached that of the dark-green ones, however, the Chl content and
photosynthetic activity remained lower. The process of reconstitution of the photosynthetic apparatus in the re-greening leaves
was accompanied by changes in fatty acid (FA) content. The amount of the FA methyl esters was more than 2-fold higher in the
green leaves as compared to the dry ones and slightly increased after rehydration in the pale-green leaves. Among the three
main fatty acids in the leaves, oleic, palmitic and linoleic acid, the latter increased more than 3-fold during rehydration.
This acid is concentrated mainly in the glycolipids and this was an indirect indication for the restoration of the photosynthetic
apparatus. Our results showed that rehydration of X. scabrida led to a decrease of the saturated FA in parallel with an increase of the unsaturated FA, thus indicating increased membrane
permeability. The observed changes in the lipid content can be considered as a characteristic feature of X. scabrida and most probably of other poikilochlorophyllous species. 相似文献