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Ozone

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by

fritzi hammerschmidt

on 10 June 2014

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Transcript of Ozone

Effect of elevated Ozone and UV-b radiation on plants
Chapman Cycle
halogens like Br· or Cl·
NO·
OH·
Formation and destruction
of stratospheric ozone
Ozonolysis
presented by
Eva Fritzi Goldmann

Tropospheric ozone
5-10% of total ozone are located in the troposphere
additionally:
carbon monoxides
hydrocarbons
estimated preindustrial-concentration: 10ppb

today: ca. 40ppb
Why should we worry?
Why is ozone harmful to plant tissue?
ozonolysis
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?
Pathogens
favorable conditions for necrotic disease agents
negative effect on biotrophic pathogens
Microevolution
enhanced ozone resistance is inheritable
one species level: increased heterozygotes - enhances adaptability?
community level: shift towards grass species
Ozone, elevated carbon dioxide &
C- sequestration
Discussion
What improvements in plant breeding could be favorable for enhanced ozone resistance?
Consequences ?
passed through stomata and leaf internal air space dissolves in water
hydroxyl and peroxyl radicals
timing of exposure of major importance
e.g. soybean
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?
UV-b radiation
Elevated ozone level - consequences for c-sequestration?
high energetic waves target DNA, proteins and membranes
formation of radicals
alteration of photosynthesis - proteins in PSII
defence mechanisms

leaf thickness
epicuticular waxes
secondary metabolites
Full transcript