L. Guidi et al., THE USE OF CHLOROPHYLL FLUORESCENCE AND LEAF GAS-EXCHANGE AS METHODS FOR STUDYING THE DIFFERENT RESPONSES TO OZONE OF 2 BEAN CULTIVARS, Journal of Experimental Botany, 48(306), 1997, pp. 173-179
After exposure to 80 ppb of ozone for a single 4 h period, a significa
nt reduction in photosynthetic activity was rapidly induced in two cul
tivars of Phaseolus vulgaris, cv. Pinto, O-3-sensitive and cv. Groffy,
O-3-resistant. Pinto displayed a strong and irreversible reduction in
A(max)anied by stomatal closure and an increase in intercellular CO,
concentration. The fluorescence parameters indicated that the electron
transport around PSII had been altered. The increase in non-photochem
ical quenching was related to an energy dissipation through non-radiat
ive mechanisms. Photosynthesis was also reduced in the cv. Groffy, but
the effect was reversible with time. Groffy showed alteration in the
photochemical functioning of the thylakoids and specific disturbances
of the water-splitting enzyme system of PSII, but these alterations di
sappeared only 20 h after the end of fumigation. Recovery of photosynt
hetic ability was more delayed with time and needed 7 d to show values
similar to the controls. Physiological tools, such as gas exchange an
d chlorophyll fluorescence, play a major role in the early detection o
f environmental stress such as O-3 pollution, and in distinguishing th
e responses between cultivars with different O-3-sensitivity.