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HELEN AGASILD PRIIT ZINGEL KATRIT KARUS KERSTI KANGRO JAANA SALUJÕE TIINA NÕGES 《Freshwater Biology》2013,58(1):183-191
1. As grazers on picoplankton and nanoplankton, planktonic ciliates form an important link in pelagic food webs. Ciliate communities may be controlled by predation by metazooplankton. In eutrophic systems, however, where the number of large crustaceans is often low, the mechanisms that regulate ciliate dynamics have rarely been described. 2. We conducted an enclosure experiment with natural and screened (145 μm) summer plankton communities to investigate the effect of the small‐sized crustacean zooplankton on ciliate community structure and the microbial loop in a shallow eutrophic lake. 3. The removal of the larger fraction of crustaceans initiated a decrease in total ciliate abundance. At the community level, we observed a substantial increase in large‐sized predacious ciliates (>100 μm) and a simultaneous decrease in the abundance of smaller ciliates (<20–40 μm) that were mostly bacterivores and bacterio‐herbivores. The compositional shift in the ciliate community, however, did not cascade down to the level of bacteria and edible phytoplankton. 相似文献
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MIKAEL BROSCHÉ EBE MERILO FLORIAN MAYER PRIIT PECHTER IRINA PUZÕRJOVA GÜNTER BRADER JAAKKO KANGASJÄRVI HANNES KOLLIST 《Plant, cell & environment》2010,33(6):914-925
Genetic variation between naturally occurring populations provides a unique source to unravel the complex mechanisms of stress tolerance. Here, we have analysed O3 sensitivity of 93 natural Arabidopsis thaliana accessions together with five O3‐sensitive mutants to acute O3 exposure. The variation in O3 sensitivity among the natural accessions was much higher than among the O3‐sensitive mutants and corresponding wild types. A subset of nine accessions with major variation in their O3 responses was studied in more detail. Among the traits assayed, stomatal conductance (gst) was an important factor determining O3 sensitivity of the selected accessions. The most O3‐sensitive accession, Cvi‐0, had constitutively high gst, leading to high initial O3 uptake rate and dose received during the first 30 min of exposure. Analyzing O3‐induced changes in stress hormone concentrations indicated that jasmonate (JA) concentration was also positively correlated with leaf damage. Quantitative trait loci (QTL) mapping in a Col‐0 × Cvi‐0 recombinant inbred line (RIL) population identified three QTLs for O3 sensitivity, and one for high water loss of Cvi‐0. The major O3 QTL mapped to the same position as the water loss QTL further supporting the role of stomata in regulating O3 entry and damage. 相似文献
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