Ozone flux to Picea sitchensis (Bong) Carr and Picea abies (L) Karst during short episodes and the effects of these on transpiration and photosynthesis.
Sitka spruce and Norway spruce were grown in controlled environments and then exposed to ozone (O3) for short periods as in mid-afternoon episodes experienced in the forest. For concentrations of between 20 and 300 nl litre(-1) there were linear relationships between exposure concentration and O3 uptake rates. Increasing photon flux densities increased rates of photosynthesis and transpiration, the increases being larger in actively growing than dormant seedlings. Physiological condition (dormancy or active growth), species and photon flux density were found to influence O3 flux via their effects on stomatal conductance. Exposure to 80 nl litre(-1) O3 resulted in consistent increases of stomatal conductance and there were also indications that water-use efficiency was decreased.
Freer-Smith
P H
PH
Forestry Commission, Forest Research Station, Alice Holt Lodge, Farnham, Surrey GU10 4LH, UK.
Dobson
M C
MC