Effects of exposure to ozone at different stages in the development of Plantago major L. on chlorophyll fluorescence and gas exchange

Abstract

SUMMARYSimilar ozone treatments were applied at diflferent stages of growth to a population of Plantago major L., which is as sensitive to ozone as Bel-W3 tobacco. Plants were grown from seed for 8 wk in controlled-environment chambers and exposed to 70 //I O., 1"^ 7 h d"' for the whole period or for 2-wk episodes during weeks 1 + 2, 3+4, 5 _l _ (, or 7 + 8. Controls had charcoal-filtered air. Effects on stomatal conductance, chlorophyll fiuorescence and net photosynthesis are described.The fluorescence character, /i, proved to be very sensitive to ozone, and it responded at all stages of plant development, but the ratio of variable to maximum fiuorescence decreased only when plants received ozone during the first 2 wk of growth. The reduction was caused by a drop in maximum fluorescence. Ozone had no effect on Whenever exposure occurred, O., significantly reduced net CO., assimilation and increased stomatal conductance. Unlike ti, the effects were persistent, affecting leaves that were in bud or enshrouded by leaves when the exposure occurred. It is suggested that these persistent effects may have been caused by changes in resource allocation, fiowering and senescence, which resulted in altered hormonal balance.

Effects of ambient O₃ on wheat during reproductive development: Gas exchange, photosynthetic pigments, chlorophyll fluorescence, and carbohydrates

“…The reduction in F m in NFCs/OPs may be due to n decline in the ability to reduce the primary acceptor Q A (Reiling and Davison 1994). Reductions recorded in variable fluorescence (F v ) are more strongly correlated with lowering of F m during the present study, suggesting impairment of an electron transport, which involves a recombination reaction P680(+) and reduced phaeophytin Phaeo(-) within PSII or directly affecting a PSII antenna system (Ishii et al 2004).…”

The impact of ozone fumigation and fertilization on chlorophyll fluorescence of birch leaves ( Betula pendula )

“…However, preceding leaf destruction, the carbon uptake capacity of the single leaves, which is the ultimate prerequisite for growth, is also decreased by ozone (Sasek and Richardson 1989;Schweizer and Arndt 1990). The declining CO 2 assimilation can be traced back to the biochemical level: quantity and activity of rubisco were found to be lowered under O 3 stress (Dann and Pell 1989;Landry and Pell 1993), while measurements of chlorophyll fluorescence also proved that the light reactions of photosynthesis were affected (Schreiber et al 1978;Schmidt et al 1990;Ruth and Weisel 1993;Mikkelsen and Ro-Poulsen 1994;Reiling and Davison 1994). The chloroplasts are probably impaired by an overall disturbed cell metabolism rather than by direct O 3 impact, because most ozone (in the concentrations prevailing in the ambient air) is absorbed in the apoplast and plasmalemma (Urbach et al 1989;Luwe et al 1993).…”

Physiological changes on agricultural crops induced by different ambient ozone exposure regimes

“…Were experienced m 1994 and 199s with monthly mean concentrations of c. 130/(gm ' can aff'ect photosynthesis and storage (sink) organs of plants (Cooley & Manning, 1987;Reiling & Davison, 1994;Pleijel et al, 1995), Photosynthesis is disturbed by ozone, and (stress) factors which influence stomatal conductivity clearly affect uptake of ozone and consequently its impact (Fuhrer, 1995;Griinhage & Jager, 1996), Since Laisk, Kull & Moldau (1989) showed that the chloroplast in the mesophyll cell is not directly damaged by ozone, it is widely accepted that the first target within at cellular level within the leaf must be the plasma membrane (Willenbrink & Schatten, 1993;Mortensen & Engvild, 1995;Sandelius et al, 1995), This view is strengthened by measurements of antioxidants in the apoplast which are part of the plant defence system against oxygen radicals (Luwe & Heber, 1995;Polle & Rennenberg, 1994), and by investigations which show premature senescence of wheat leaves as a result of ozone exposure, as suggested by Lehnherr et al (1987) and Soja & Soja (1995), However, if sucrose accumulates in leaf cells, it might cause down-regulation of photosynthesis (Jang & Sheen, 1996;Pollock & Farrar, 1996) which could occur as a consequence of disturbance of the overall phloem loading process by previous damage to the mesophyll plasma membrane, and not only by reducing sink strength (Heath, 1987), Down-regulation of photosynthesis might result in photoinhibition, particularly if the defence systems again oxygen radicals within the mesophyll are diverted towards the apoplast. In order to get information on early physiological response of crop plants to ozone regimes which were monitored in North-Rhine Westphalia during the last years, spring wheat grown in a charcoal-filtered glasshouse was fumigated in specially designed exposure chambers for 14 d, during the main developmental stages.…”