The ozone sensitivity of birch (Betula pendula) in relation to the developmental stage of leaves

Abstract

St;MMARYClonal birch (Betula peiidula Roth.) seedlings at three different de\ elopmental stages were fumigated for 12 h daily with 50, 90 and 1 30 ppb ozone for 25 d. When transferred to fumigation chambers, the leaves of plant group 1 were almost expanded, in group 2 they were fast enlarging, and in group 3 all the leaves emerged under the exposure. The plants in which the lea\es emerged under the ozone stress were the most resistant to ozone. In groups 1 and 2 ozone treatments reduced the growth of leaf biomass. and induced more visible injuries on leaves and ultrastructural symptoms in chloroplasts than they did in group 3. The stomatai densjt> of leaves increased in response to ozone in all the groups, Tbe effects of ozone on stomatal conductance were complex. In groups 1 and 2 the 50 ppb ozone exposure increased stomatal conductance whereas lowered conductances were observed in group 3 after fumigation with 90 and 130 ppb ozone. The results suggest that the leaves developing under ozone fumigation were better able to tolerate tbe ozone stress, as indicated by unaffected or stimulated growtb and small amounts of \-isible and ultrastructural injuries and stomatal cbanges. It is possible to regard the changes as acclimation reactions.

Ozone-Induced Changes in Antioxidant Systems of Ginkgo Biloba in Relation to the Developmental Stage of the Leaves

“…Consistently, the higher resistance of younger leaves to O 3 stress has been reported in other tree species [18][19][20], but the reasons seem unclear. It was supposed that remobilization of resource from senescing leaves to younger ones could allow the latter to withstand ozone stress [21], but this hypothesis needs more experiments to test.…”

Physiological, biochemical and molecular responses to a combination of drought and ozone in Medicago truncatula

“…Down-regulation of XET gene family members in response to low water potential in soybeans and tobacco decreased cell wall extensibility but increased wall thickness that could prevent water loss (Herbers et al 2001;Wu et al 2005). On the contrary, up-regulation of XETs in response to ozone may promote wall biogenesis and increase in cell or stomatal density as observed in birch tress (Gunthardt-Goerg et al 1993;Paakkonen et al 1995;Frey et al 1996;Kontunen-Soppela et al 2010). This increase in cell number may aid in even ozone distribution within leaf tissues for efficient detoxification processes (Paakkonen et al 1995;Hetherington & Woodward 2003).…”

“…On the contrary, up‐regulation of XETs in response to ozone may promote wall biogenesis and increase in cell or stomatal density as observed in birch tress (Gunthardt‐Goerg et al . 1993; Paakkonen et al . 1995; Frey et al .…”

“…2010). This increase in cell number may aid in even ozone distribution within leaf tissues for efficient detoxification processes (Paakkonen et al . 1995; Hetherington & Woodward 2003).…”

“…On the contrary, up-regulation of XETs in response to ozone may promote wall biogenesis and increase in cell or stomatal density as observed in birch tress (Gunthardt-Goerg et al 1993;Paakkonen et al 1995;Frey et al 1996;Kontunen-Soppela et al 2010). This increase in cell number may aid in even ozone distribution within leaf tissues for efficient detoxification processes (Paakkonen et al 1995;Hetherington & Woodward 2003). Thus, transgenic approaches modulating XET gene expression may not deliver the desired impact when combined ozone and drought stress are operative simultaneously.…”