[show abstract]
[hide abstract]
ABSTRACT: We present here the effects of ambient ozone (O3)-induced decline in carbon availability, accelerated foliar senescence, and a decrease in aboveground biomass accumulation
in the Aleppo pine (Pinus halepensis Mill.). Aleppo pine seedlings were continuously exposed in open-top chambers for 39months to three different types of O3 treatments, which are as follows: charcoal-filtered air, nonfiltered air (NFA), and nonfiltered air supplemented with 40ppb
O3 (NFA+). Stable carbon isotope discrimination (Δ) and derived time-integrated c
i/c
a ratios were reduced after an accumulated ozone exposure over a threshold of 40ppb (AOT40) value from April to September
of around 20,000ppb·h. An AOT40 of above 67,000ppb·h induced reductions in ribulose-1,5-biphosphate carboxylase/oxygenase
activity, aboveground C and needle N and K concentrations, the C/N ratio, Ca concentrations in twigs under 3mm, and the aerial
biomass, as well as increases in needle P concentrations and phosphoenolpyruvate carboxylase (PEPC) activity and the N and
K concentrations in twigs under 3mm. Macronutrients losses, the limitations placed on carbon uptake, and increases in catabolic
processes may be the causes of carbon gain diminution in leaves which was reflected as a reduction in aboveground biomass
at tree level. Stimulation of PEPC activity, the consequent decreased Δ, and compensation processes in nutrient distribution
may increase O3 tolerance and might be interpreted as part of Aleppo pine acclimation response to O3.
KeywordsAleppo pine-Δ-Rubisco-PEPC-Tree productivity-Plant nutrition
Water Air and Soil Pollution 04/2012; 214(1):587-598. · 1.63 Impact Factor
