Using open-top chamber technology, we investigated the foliar phenolic
response of common bean (Phaseolus vulgaris L. cv.
Bergamo) to a chronic, moderate ozone stress. Three atmospheric concentrations
of ozone were tested: non-filtered air (NF) prevailing at the experimental
site, and non-filtered air supplied with 40 (NF+40) and 60 nL
L–1 ozone (NF+60), respectively. Both
constitutive and ozone-induced non-polymerized phenolics were considered with
regards to pollutant concentration, exposure time, leaf type (primary or
trifoliate), and leaf growth. The biomass of primary leaves was unaffected by
the tested ozone concentrations, whereas dry mass of first and second
trifoliate leaves significantly decreased as atmospheric ozone increased.
Characteristic symptoms were observed on the upper surface of leaves from the
two ozone-supplied treatments. Their severity reflected both leaf exposure
time and ozone concentration. As a whole, the total content of foliar soluble
constitutive phenolics remained unchanged as the ozone increased, even for
leaves almost totally covered with dark-brown discolourations. Nonetheless,
among the three main detected phenolics, the accumulation of the kaempferol
derivative could be significantly stimulated by ozone. Also, six ozone-induced
phenolics could be synthesized by leaves exposed to the two pollutant-enriched
atmospheres, and their elicitation and amount were closely connected with both
exposure time and ozone concentration.
Leaf phenology and insect grazing of Japanese white birch saplings grown under free-air ozone exposure