Impairment of gas exchange and structure in birch leaves (Betula pendula) caused by low ozone concentrations

Abstract

Injury caused by low 03 concentrations (0, 0.05, 0.075, 0.1 gl 1-1) was analyzed in the epidermis and mesophyll of fully developed birch leaves by gas exchange experiments and low-temperature SEM: (I) after leaf formation in O3-free and ozonated air, and (II) after transferring control plants into ozonated air. In control leaves, autumnal senescence also was studied in O3-free air (III). As 03 concentration increased, leaves of (I) stayed reduced in size, but showed increased specific weight and stomatal density. The declining photosynthetic capacity, quantum yield and carboxylation efficiency lowered the light saturation of CO2 uptake and the water-use efficiency (WUE). Carbon gain was less limited by the reduced stomatal conductance than by the declining ability of CO2 fixation in the mesophyll. The changes in gas exchange were related to the 03 dose and were mediated by narrowed stomatal pores (overriding the increase in stomatal density) and by progressive collapse of mesophyll cells. The air space in the mesophyll increased, preceded by exudate formation on cell walls. Ozonated leaves, which had developed in O3-free air (II), displayed a similar but more rapid decline than the leaves from (I). In senescent leaves (III), CO2 uptake showed a similar decrease as in leaves with 03 injury but no changes in mesophyll structure and WUE. The nitrogen concentration declined only in senescent leaves in parallel with the rate of CO2 uptake. A thorough understanding of 03 injury and natural senescence requires combined structural and functional analyses of leaves.

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

“…The higher stomatal density in clones A, D and E, and the lower stomatal conductance in our exposures agree with previous results for Betula pendula (Matyssek et al, 1991). Reduced stomatal conductance in response to ozone exposure has been found earlier also in Populus deltoides x trichocarpa (Reich & Lassoie, 1984), Gossypium hirsutum L. (Temple, 1986) and Populus maximowizii x trichocarpa (Pell, Eckardt & Enyedi, 1992) and therefore seem to be a consistent phenomenon related to ozone stress.…”

“…Reduced leaf biomass may be a result of disturbed photosynthesis and declined production, these being well known responses to ozone stress (e.g. Darrall, 1989;Matyssek et al, 1991;Pell et al, 1992), Ozone has been reported to cause a wide array of visible symptoms depending on the type and variety of plant, the concentration and duration of O3 exposure, and other interacting factors (Krupa & Manning, 1988). In birch, Matyssek e« a/.…”

Effects of ozone exposure on growth and photosynthesis of beech seedlings (Fagus sylvatica)

“…It is now assumed that stomatal closure is not a direct effect of ozone, but a reaction to an increased internal CO # concentration resulting from the inhibition of carbon assimilation (Reich, 1987 ;Heath & Taylor, 1997). Several authors have reported oscillations in gas exchange and uncoupling of the relationship between A and g s (Matyssek et al, 1991 ;Flagler et al, 1994 ;Tjoelker et al, 1995 ;Clark et al, 1996) and have attributed this to loss of stomatal control ; this was not observed in the present experiment. Stomatal conductance in the elevated treatments was slightly reduced during the exposure period, but remained correlated with photosynthetic rates (K. Bortier, unpublished).…”

Ozone‐induced accumulation of carbohydrates changes enzyme activities of carbohydrate metabolism in birch leaves

“…Gas exchange of leaves of different age classes from the main axis was measured shortly before harvest using an open gas-exchange system (Walz, Effeltrich, Germany) as described by Matyssek et al (1991). The rate of net photosynthesis was calculated according to von Caemmerer & Farquhar (1981) and was based on the one-sided leaf area which was determined with the Delta-T area meter MK2.…”