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Transcript of Ozone
halogens like Br· or Cl·
Formation and destruction
of stratospheric ozone
Eva Fritzi Goldmann
5-10% of total ozone are located in the troposphere
estimated preindustrial-concentration: 10ppb
today: ca. 40ppb
Why should we worry?
Why is ozone harmful to plant tissue?
enables ozone to split up multi carbon-carbon bounds
replaced by double bound to oxygen
lipids - membrane
can be oxidized to form alcohols, aldehydes, ketones or carboxylic acids
What protection mechanisms do exist?
favorable conditions for necrotic disease agents
negative effect on biotrophic pathogens
enhanced ozone resistance is inheritable
one species level: increased heterozygotes - enhances adaptability?
community level: shift towards grass species
Ozone, elevated carbon dioxide &
What improvements in plant breeding could be favorable for enhanced ozone resistance?
passed through stomata and leaf internal air space dissolves in water
hydroxyl and peroxyl radicals
timing of exposure of major importance
reduced net assimilation due to
damage in thylacoid membrane
decreased RuBisCo activity
ROS = Reactive Oxygen Species
HOO· ROO· HO·
combat oxidative stress with enzymes that use ascorbic acid and glutathione
antioxidant & signaling network that control plant defence responses and leaf senescence
resistance: higher extracellular ascorbat content
effect depending on climate conditions like humidity, soil moisture, leaf temperature and insolation
FACE experiments with elevated carbon dioxide and elevated ozone
prevent reductions in yield and growth
unable to prevent accelerated senescence
elevated ozone lowers root biomass ratio due to translocation inhibition
Why does an elevated carbon dioxide level prevent yield reduction in crops exposed to toxic ozone levels?
How could an elevated environmental ozone level be responsible for accelerated leaf senescence?
Elevated ozone level - consequences for c-sequestration?
high energetic waves target DNA, proteins and membranes
formation of radicals
alteration of photosynthesis - proteins in PSII