Differences in the structural reactions of leaves exposed to elevated levels of controlled versus ambient ozone in Fraxinus ornus. (Contributo in atti di convegno)

Type
Label
  • Differences in the structural reactions of leaves exposed to elevated levels of controlled versus ambient ozone in Fraxinus ornus. (Contributo in atti di convegno) (literal)
Anno
  • 2006-01-01T00:00:00+01:00 (literal)
Alternative label
  • Bernasconi P., Vollenweider P., Paoletti E., Günthardt-Goerg M.S. (2006)
    Differences in the structural reactions of leaves exposed to elevated levels of controlled versus ambient ozone in Fraxinus ornus.
    in Impacts of Air Pollution and Climate Change on Forest Ecosystems. Forests under Influence of Air Pollution, Climate Change and Urban Development., Riverside, California
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Bernasconi P., Vollenweider P., Paoletti E., Günthardt-Goerg M.S. (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#descrizioneSinteticaDelProdotto
  • Validating the effects of ambient ozone in the leaves with experimental exposure in controlled conditions is generally complicated by the varying reactions of plants to differing environmental conditions and plant age. In this study, structural reactions of two year old seedlings treated in fumigation chambers were compared to those in leaves collected from mature trees in the field. Seedling leaves were sampled after a 7 week exposure to charcoal-filtered air vs. 150 ppb ozone during 8 h per day (AOT40 = 43.1 ppm h) in closed chambers with a low supply of light (PPFD = 500 ìmol m-2 s-1). The ozone treated samples showed 20 % of their leaf area with ozone-induced symptoms. Asymptomatic and symptomatic (20-35 % of leaf area) leaves were sampled in September 2004 from the top and light-exposed crown of four mature trees growing in the field (Settignano, Florence, Italy; AOT40 = 21.3 ppm h in 2004). The leaf samples were immediately fixed upon sampling prior to processing in the lab in view of the planned analyzes in transmitted and fluorescent light microscopy. The morphology of leaves in seedlings showed some juvenile and shade leaf characteristics whereas that in mature trees was typical for leaves grown in full sunlight and collected at the end of the vegetation season. An ozoneinduced stippling was found in leaves of seedlings and was underlain with dead and collapsed cells showing little disruption of the cell content; these structural changes signaled rapid HR-like reactions and were not distributed along gradients of light exposure. Leaves from the field showed bronzing caused by light-dependent gradients of stress reactions and accumulations of phenolic defense compounds at the cell and tissue level; these alterations indicated an accelerated senescence process due to synergic effects between light and ozone stress. Both seedlings and mature trees thus developed typical ozone symptoms in their leaves but not with the same combination of ozone stress markers. Light stress, a lower ozone dose and cumulative effects during longer exposure strongly contributed to differentiate the symptom expression in mature vs. juvenile trees. In conclusion, this study documents the plasticity of the leaf reactions in Fraxinus ornus and shows its dependency on the ozone exposure, environmental conditions and plant maturity. (literal)
Titolo
  • Differences in the structural reactions of leaves exposed to elevated levels of controlled versus ambient ozone in Fraxinus ornus. (literal)
Prodotto di
Autore CNR
Insieme di parole chiave

Incoming links:


Prodotto
Autore CNR di
Insieme di parole chiave di
data.CNR.it