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Timing of ozone stress and resulting status of ribulose bisphosphate carboxylase/oxygenase and associated net photosynthesis
Author(s) -
PELL E. J.,
ECKARDT N.,
ENYEDI A. J.
Publication year - 1992
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1992.tb01080.x
Subject(s) - rubisco , photosynthesis , ribulose 1,5 bisphosphate , oxygenase , pyruvate carboxylase , stomatal conductance , horticulture , botany , ozone , ribulose , carboxylation , biology , chemistry , biochemistry , enzyme , organic chemistry , catalysis
summary Experiments were conducted to determine how the timing of an exposure to ozone influenced the impact of the gas on ribulose‐ 1,5‐bisphosphate carboxylase/oxygenase (Rubisco) throughout the life span of a designated leaf. Saplings of Populus maximowizii × trichocarpa NE 388 received 5‐d exposures to O 3 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 of the protein in the leaf. When the concentration of Rubisco was near its peak, O 3 induced a reduction in quantity and activity of Rubisco, but after cessation of the O 3 stress, levels converged with those of the untreated tissue. When O 3 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 O 3 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 2 response curves were measured periodically, and the initial slope (linear portion) of the curve, reflecting carboxylation capacity, declined more rapidly with leaf age in O 3 ‐treated than in untreated poplars. There was no effect of O 3 on stomatal limitation to CO 2 , assimilation except for a slight increase during the last 2 wk of the 9‐wk experiment. This supported the hypothesis that O 3 effects on A were associated with CO 2 ‐fixing capability of the leaf.