Possible mechanisms for the inhibition of photosynthesis by ozone

Abstract

Tropospheric ozone produced by industrial civilization is widespread. Although the levels are not clearly life threatening, they do have the potential to inhibit normal plant productivity, thought to be by an inhibition of photosynthesis. While the mechanism for this inhibition is not yet clear, there are several hypotheses for its cause. It is unlikely that ozone can penetrate the cell membrane unreacted; therefore, reactions at the plasma membrane either causing general ionic and metabolic disturbance within the cell or causing the production of unidentified toxic products must ultimately produce the alterations within the chloroplasts. While model systems, such as individual biochemicals, isolated chloroplasts, and algae, can give some understanding of possible reactions, they cannot provide the full story. One continuing controversy revolves about the role of stomata in the inhibition process-they play an important role, but the full interaction between stomatal closure and inhibition of photosynthesis has not yet emerged. In order to reach a political compromise on air quality standards, we need to have a good understanding of the fundamental mechanisms by which ozone causes any decline in plant productivity.

Enhanced Stomatal Conductance by a Spontaneous Arabidopsis Tetraploid, Me-0, Results from Increased Stomatal Size and Greater Stomatal Aperture

“…The most significant gene sets, which were enriched in up-regulated genes, were related to plant-type cell wall loosening, an essential step in guard cell swelling (Wei et al, 2011). In down-regulated genes, there were several significant gene sets related to the defense responses for immunity, hypoxia, and ozone, which also influence stomatal responses or gas exchange (Heath, 1994;Melotto et al, 2006;Gil et al, 2009). Microarray analysis demonstrated that these gene expression differences may be related to the differences in stomatal aperture between Me-0 and tetraploid Col evaluated in Figure 3.…”

Assessing leaf pigment content and activity with a reflectometer

“…For example, pigment content and related physiological properties vary with ontogeny (Sestak, 1985), senescence (Gausman et al, 1971 ;Adams et al, 1990 ; *Author for correspondence (fax j1 323 343 6451 ; e-mail jgamon!calstatela.edu). 1995), nitrogen content (Khamis et al, 1990), air pollution exposure (Heath, 1994 ;Wellburn, 1994), light history (Thayer & Bjo$ rkman, 1990) and functional type (Gamon et al, 1997). Consequently, reflectance assessment of leaf pigments can potentially provide useful indicators of integrated leaf physiology under a wide range of conditions.…”

Adverse effects of ambient ozone on watermelon yield and physiology at a rural site in Eastern Spain

“…In addition, leaf gas exchange measurements performed in both the laboratory and the field revealed a higher c i \c a ratio in O $ -exposed foliage. As it is considered extremely unlikely that O $ (and\or its primary reaction products) causes the oxidation of Rubisco protein itself (Heath, 1994b ;Lyons et al, 1999), further research needs to address the signal transduction pathway(s) triggering the decline in Rubisco activity and\or content under the influence of O $ . Interestingly, the laboratory-based studies revealed an O $ -induced decline in J max in addition to effects on V c,max , suggesting that more than one site within the photosynthetic apparatus was perhaps affected by the pollutant.…”