P. Ramge et al., APOPLASTIC ANTIOXIDANTS AS DECISIVE ELIMINATION FACTORS WITHIN THE UPTAKE PROCESS OF NITROGEN-DIOXIDE INTO LEAF TISSUES, New phytologist, 125(4), 1993, pp. 771-785
Uptake of NO2 via stomata and its elimination in the mesophyll are inv
estigated by use of mathematical models. Systems of differential equat
ions describe simultaneous diffusion and reaction of the chemical spec
ies taken into account. The common hypothesis, postulating the disprop
ortionation reaction of NO2 being the predominant path for the transfo
rmation of NO2 into the cellular nitrate and nitrite pools, could be f
alse because of its failure to reproduce the measured sorption charact
eristics. If however the reduction of the pro-oxidative NO2 by apoplas
tic ascorbate is taken into account the calculated uptake rates and th
e effects of changes in immission concentration and vegetational chara
cteristics fit well within corresponding experimental results. The ons
et of acute injury in case of a fall in apoplastic ascorbate concentra
tion below a critical level is postulated.