Growth and stomatal responses of birch (Betula pendula Roth.) clones to ozone in open‐air and chamber fumigations

Abstract

SUMMARYIt is evident that even outside the classical high ozone areas some plant species are at risk. In this study seedlings of five birch clones {Betula pendula Roth.) were exposed to a slightly elevated ozone level in an open-field experiment over two growing seasons. The ozone doses were 1-2 x (1991) and 1-5 x (1992) higher than the ambient. The clones were also fumigated with 150 nl 1 ' ozone for 24 d (12 h d"^) in a chamber experiment. They were found to differ in their susceptibility to ozone: ozone fumigation decreased the height growth and leaf biomass, and increased the amount of advanced visible injury in leaves of the most sensitive clone, but did not affect the height growth or amount of visible injury of the most tolerant clone. The other three clones were intermediate with respect to their sensitivity to ozone. In all clones, elevated O., concentrations increased diffusive resistance to water vapour but increased the stomatal density in the emerging leaves. The appearance of autumn colouririg was accelerated in the field experiments. The results support the conclusion that birch populations in Finland can be negatively affected by ozone. The effect is most likely in sensitive birch individuals during ozone episodes.

The effects of ozone and nutrient supply on stomatal response in birch (Betula pendula) leaves as determined by digital image‐analysis and X‐ray microanalysis

“…Both factors influenced the stomatal density. Increased stomatal density in birch seems to be a consistent efFect related to ozone exposure and has also been reported by Matyssek et al (1991), Gunthardt-Goerg et al (1993«) and Paakkonen et al (1993). The increased stomatal density was apparently overridden by the narrowing stomatal apertures.…”

Differential tolerance to copper and zinc of micropropagated birches tested in hydroponics

“…This clone was formerly commercially propagated in vitro by Enso-Gutzeit, Ltd., Imatra, Finland, and has recently been shown to be relatively tolerant to ozone (Paakkonen et al, 1993).…”

Responses to ozone in 12 provenances of European beech (Fagus sylvatica): genotypic variation and chamber effects on photosynthesis and dry‐matter partitioning

“…One complication is that mature trees may not respond like seedlings. Another complication is that different provenances (Larsen et al, 1990 ;Mortensen, 1994), families (Taylor, 1994), and even clones (Pa$ a$ kko$ nen et al, 1993) might respond differently to O $ . In general, trees respond to O $ by reduced root growth rather than reduced shoot growth, resulting in an increased shoot : root ratio (Sellde!…”