Timing of ozone stress and resulting status of ribulose bisphosphate carboxylase/oxygenase and associated net photosynthesis

Abstract

Experiments were conducted to determine how the timing of an exposure to ozone influenced the impact of the gas on ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco) throughout the life span of a designated leaf. Saplings of Populus maximowizti x trichocarpa XE 388 received 5-d exposures to O^ in growth chambers during and at the termination of presumed synthesis of Rubisco in a designated leaf. Ozone had no detectable impact on Rubisco activity or quantity when the exposure occurred during the time of increasing concentration oi the protein in the leaf. When the concentration of Rubisco was near its peak, O^ induced a reduction in quantity and activity of Rubisco, but after cessation of the O^ stress, levels converged with those of the untreated tissue. When Og exposure occurred after full leaf expansion, minimal effects of the gas could be detected. When plants of hybrid popular or Raphanus sativus L. cv. Cherry Belle received chronic O3 treatment throughout the lifespan of the leaf, Rubisco activity and quantity' declined more rapidly and never converged with values of untreated tissue.Studies of gas exchange revealed that changes in Rubisco were associated with a decline in net photosynthesis (A) and that these effects preceded the observed reduction in foliar conductance. CO, response curves were measured periodically, and the initial slope (linear portion) of the curve, reflecting carboxylation capacity, declined more rapidly with leafage in O^-treated than in untreated poplars. There was no effect of O^ on stomatal limitation to COj assimilation except for a slight increase during the last 2 wk of the 9-wk experiment. This supported the hypothesis that O^ effects on A were associated with CO^-fixing capability of the leaf.

A comparison of sensitivity to ozone in seedlings and trees of Quercus rubra L.

“…Similarly, co.-occurring reductions in photochemical and photosynthetic processes were reported for Pinus taeda L. seedlings in response to three seasons of fumigation with 92 ppb ozone (Sasek & Richardson, 1989). Pell, Eckardt & Enyedi (1992) observed a direct effect of ozone on the COj-fixing capabilities of Populus maximowizii X trichocarpa leaves.…”

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

“…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/.…”

Response of radish to multiple stresses

“…Ozone effects on stomatal conductance were insignificant in the spring (data not shown). In the autumn Cherry Belle exhibited an 03-induced reduction in stomatal conductance as previously reported (Pell et aL, 1992). Both genotypes exhibited similar conductance rates within and across seasons so only results for Cherry Belle are illustrated.…”

“…Leaf conductance was determined five times during each experiment by methods previously described (Pell, Eckardt & Enyedi, 1992). Measurements were determined for the oldest leaf on the plant and were followed throughout the maturing process.…”