milkweed

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Presentation materials prepared by Ed Jepsen, DNR Air Management Biomonitoring Unit: 

Presentation materials prepared by Ed Jepsen, DNR Air Management Biomonitoring Unit Ground Level Ozone and Common Milkweed

Ground Level Ozone: 

Ground Level Ozone Ozone (Smog) is the most damaging regional air pollutant in the United States

Areas in the U.S. with High Seasonal Ozone Exposures: 

Areas in the U.S. with High Seasonal Ozone Exposures

Slide4: 

foliar injury in natural ecosystems 8 to 12 ppm-hrs growth effects on tree seedlings/saplings 10 to 16 ppm-hrs 10% yield reductions in crops 15 to 20 ppm-hrs All below a proposed 25.5 ppm-hrs seasonal standard Ozone Injury Thresholds

Slide5: 

When does ozone injury occur? genetically sensitive have adequate growing conditions ozone exposure must exceed tolerance Plant must be: Injury can occur in very sensitive species at chronic hourly exposures of 60 ppb

Effects of Ozone on Plants: 

Effects of Ozone on Plants reduced reproduction reduced photosynthesis reduced height & diameter changes in forest ecosystems weakens sensitive plants to insect/disease stresses Chamber and Field studies have shown:

Common Milkweed : 

Common Milkweed Milky juice Simple stem 1-6 ft tall Hairy leaf Common along roadsides, open fields & disturbed areas

Ozone Indicator Species: 

Ozone Indicator Species Milkweed Black Cherry Blackberry Tulip Poplar White Ash Sassafras Sweetgum Pin Cherry Spreading Dogbane Big leaf Aster

Slide9: 

Ozone enters through stomata and attacks the photosynthetically active cells. Palisade layer cell membranes and chemistry are adversely affected.

Elevated ozone exposures can kill cells: 

Elevated ozone exposures can kill cells Dead palisade cells on the upper leaf surface cause the black stipple appearance