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Effect of elevated CO2 on morphological and photosynthetic parameters in two understory grass species in Beskydy Mountains
Holub, Petr ; Klem, Karel ; Urban, Otmar
We transplanted two grass species, Calamagrostis arundinacea and Luzula sylvatica, to the understory of\na 10-year-old experimental mixed forest exposed to ambient (385 μmol CO2 mol–1, AC) and elevated (700\nμmol CO2 mol–1, EC) atmospheric CO2 concentration using a glass dome facility. Effects of EC on plant\nmorphology and photosynthesis were examined after three years of treatment. We tested the hypotheses\nthat shade-tolerant species can profit from EC even at low light conditions and that relatively low accumulation\nof assimilates at such light conditions will not cause CO2-induced down-regulation of photosynthesis.\nWe expected that EC can substitute insufficient light intensities under the tree canopy and lead to both\nhigher biomass production and survival of plants in deep forest understories. The typical shade-tolerant\nspecies L. sylvatica exhibited positive acclimation under EC allowing higher light use efficiency under subsaturating\nlight intensities as compared to plants grown under AC. In contrast, C. arundinacea showed\nhigher stimulation of growth and photosynthetic rates by EC mainly under saturating light intensities at\nthe beginning of the growing season, when the forest leaf area is not fully developed and the open canopy\nallows a greater proportion of incident light to reach the understory. Our data indicate that growth and\nphysiological responses of EC plants in forest understories are species specific, differ from responses of\nsun-exposed plants, and depend on degree of shading.
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Effects of UV radiation and drouhgt on the accumulation of UV-screening compounds and photosynthetic parameters in selected herbs and grasses of the mountain grassland ecosystem
Klem, Karel ; Holub, Petr ; Urban, Otmar ; Rajsnerová, Petra ; Kubásek, Jiří
The main objective of the experiment conducted on a mountain grassland ecosystem was to investigate the interactive eff ects of UV treatment and drought on the changes in accumulation of UV-screening compounds and photosynthetic parameters in selected herb (Hypericum maculatum) and grass (Agrostis tenuis) species. Th e experimental plots were manipulated using roof constructions enabling exclusion or transmission of incident precipitation and UV radiation, respectively. Generally, UV and drought treatments had a similar eff ect on the accumulation of fl avonols. UV exclusion resulted in a slight reduction of UV-screening compounds, particularly under the conditions of ambient precipitation. Likewise, drought treatment caused an increase in the accumulation of fl avonols per area unit. Under UV exclusion, drought slightly reduced the light-saturated CO2 assimilation rate (Amax) in both the species studied. Th e presence of UV radiation, however, led to less of a diff erence in Amax between [wet] and [dry] treatments. In addition to the increased induction of fl avonols, UV radiation increased water use effi ciency and alleviated thus the negative impact of drought on photosynthesis.
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