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2. Control mechanisms of photosynthetic capacity under elevated CO2 concentration: evidence from three experiments with Norway spruce trees

Creator:
Urban, O., Pokorný, R., Kalina, J., and Marek, M. V.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
down-regulation, nitrogen, Picea abies, sing strength, and sun and shade needles
Language:
Multiple languages
Description:
Twelve-year-old Norway spruce (Picea abies [L.] Karst.) were exposed to ambient (AC) or elevated (EC) [ambient + 350 μmol(CO2) mol-1] CO2 concentration [CO2] using the facilities of open-top-chambers (OTCs) and glass domes (GDs). A combination of gas exchange measurements and application of a biochemical model of photosynthesis were used for the evaluation of CO2 assimilation characteristics. Morphological change was assessed on the base of specific leaf area (SLA). Nitrogen (N) content in the assimilation apparatus was considered a main factor influencing the biochemical capacity. Three experiments confirm the hypothesis that an adjustment of photosynthetic capacity under EC is controlled by the combination of biochemical, morphological, and physiological feedback mechanisms. We observed periodicity of down-regulation of photosynthetic capacity (Experiment No. 1) during the vegetation seasons. In the spring months (May-June), i.e. during the occurrence of active carbon sink associated with the formation of new foliage, up-regulation (10-35 %) of photosynthetic capacity (PNsat) was observed. On the contrary, in the autumn months (September-October) down-regulation (25-35 %) of PNsat was recorded that was mainly associated with reduced carbon sink strength and biochemical change, i.e. decrease of N status (up to 32 %) and accumulation of saccharides (up to 72 %) in leaves. Different adjustments of photosynthetic activities were observed in current (C) and one-year-old (C-1) needles exposed to EC (Experiment No. 2). Strong down-regulation of PNsat and the diminution of the initial stimulation of photosynthetic rate (PNmax) was associated with decreases of both ribulose-1,5-bisphosphate carboxylase/oxygenase carboxylation activity (by 32 %) and RuBP regeneration (by 40 %). This performance was tightly correlated with the absence of active carbon sinks, decrease of N content, and starch accumulation in C-1 needles. Finally, different responses of sun- and shade-adapted needles to EC (Experiment No. 3) were associated with the balance between morphological and biochemical changes. Observed PNsat down-regulation (by 22 %) of exposed needles in EC was predominantly caused by effects of both higher assimilate accumulation and stronger N dilution, resulting from higher absolute photosynthetic rates and incident irradiances in the upper canopy. and O. Urban ... t al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. Peculiarities of behaviour of taiga (Ixodes persulcatus) and sheep (Ixodes ricinus) ticks (Acarina: Ixodidae) determined by different methods

Creator:
Alekseev, Andrey N., Jensen, Per M., Dubinins, Helen V., Smirnova, Lioubov A., Makrouchina, Natalia A., and Zharkov, Sergey D.
Format:
print
Type:
model:internalpart and TEXT
Subject:
tick, exoskeleton anomalies, questing, locomotor activity, and Borrelia
Language:
English
Description:
A comparison of the behavioural peculiarities of Ixodes persulcatus Schulze, 1930 (north-western population, Russia) and Ixodes ricinus (L., 1758) from western Russia and Denmark was determined by using two methods. Method 1 involved a sojourn of ticks on vertical plastic slicks and showed that the questing behaviour of /. ricinus nymphs was dependent on temperature and relative humidity (RH). A significantly greater number of nymphs quested at 22°C and 100% RH than at 18°C. When the humidity was reduced to 30% all of the nymphs departed. In the second method, the activity of licks on an inclined “ticksdromc” was estimated. The activity of I. ricinus adults from the Danish population was 1.2 times greater than that of ticks from Russia. Females of the species studied and specimens from all study areas were more active than all other stages of development. The locomotor activity of both adult and immature I. ricinus that were infected with Borrelia burgdorferi sensu lato was suppressed when compared with uninfected specimens. The locomotor activity of I. persulcatus females infected by borreliae with exoskeleton anomalies was 1.3 times greater (PO.05) than that of infected ticks without anomalies. Our data showed that infected females with exoskeleton anomalies could crawl faster on a human and reach uncovered parts of the body that are vulnerable for attachment and feeding. A study of locomotor aclivity and questing behaviour may be useful for comparing the risk for different tick species and populations to transmit tick-borne pathogens.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Submergence effects on rice genotypes during seedling stage: Probing of submergence driven changes of photosystem 2 by chlorophyll a fluorescence induction O-J-I-P transients

Creator:
Panda, D., Rao, D. N., Sharma, S. G., Strasser, R. J., and Sarkar, R. K.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
inundation, Oryza sativa, and survival
Language:
Multiple languages
Description:
The effects of submergence on chlorophyll (Chl) a fluorescence were compared in seven Oryza sativa (L.) cultivars, namely FR 13A, Khoda, Khadara, Kalaputia (tolerant), Sabita, and Hatipanjari (avoiding type), and IR 42 (susceptible). Seedlings were submerged for 4 d under complete darkness. Oxygen concentration of flood water decreased with the period of submergence with concomitant increase in concentration of carbon dioxide. Submergence caused diminution in the amount of total Chl. Genotypic differences were observed for Chl content and survival percentage. Quantification of the Chl a fluorescence transients (JIP-test) revealed large cultivar differences in the response of photosystem 2 (PS2) to submergence. The kinetics of Chl a fluorescence rise showed complex changes in the magnitudes and rise of O-J, J-I, and I-P phases caused by submergence. The selective suppression of the J-I phase of fluorescence especially after 2 d of submergence provided evidence for weakened electron donation from the oxygen evolving complex whereas under severe submergence stress (4 d) both O-J and J-I steps were suppressed greatly with highly suppressed P-step, which resulted in lowering of variable fluorescence. Grouping probability or energetic connectivity between PS2 obtained through JIP-test from the data after 2 d of submergence showed a direct relation with survival percentage, i.e. fluorescence measurements contained the information of the survival chance of a plant under submerged conditions. The information could be used in identifying the submergence tolerant cultivars when the damage is not very severe. and D. Panda ... [et al.].
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6. Subulura halli (Ascaridida: Subuluridae) from the endangered great bustard Otis tarda Linnaeus (Aves: Gruiformes) in China

Creator:
Du, Li-Qiang, Xu, Zhen, Li, Shun-Cai, and Li, Liang
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
Nematoda, redescription, morphology, taxonomy, scanning electron microscopy, Otididae, endangered birds, and Palaearctic Region
Language:
English
Description:
Subulurid nematodes identified as Subulura halli Barreto, 1918 were collected from the endangered bird Otis tarda Linnaeus (Gruiformes: Otididae) in China. A detailed redescription of the hitherto poorly known species is presented using both light and, for the first time, scanning electron microscopy. Previously unreported and erroneous morphological features of taxonomic significance are revealed. This species can be readily distinguished from its congeners by the relatively long oesophagus (1.47-1.92 mm long, representing 10.6-16.9% of body length), the number and arrangement of male caudal papillae (11 pairs in total, arranged as five pairs of precloacal and six pairs of postcloacal papillae), the equal length of spicules (1.35-1.52 mm long, representing 10.7-13.7% of body length) and the presence of a small medioventral, precloacal papilla in the male.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public