Stomatal Conductance To Water Vapor Research Articles

Physiological responses of field-grown strawberry ( Fragaria × Ananassa duch.) exposed to acidic fog and ambient ozone

Physiological responses of field-grown strawberry ( Fragaria × ananassa Duch. Chandler) were monitored to examine the mechanistic basis of acidic fog and ambient ozone (O 3) impacts on growth and yield. Strawberry plants were exposed to simulated fog (pH 7.24, 2.69, or 1.68) twice weekly for 11 weeks, singly or in combination with ambient levels of O 3 in open-top field chambers. Applications of highly acidic fog (pH 1.68) caused significant reductions in growth, but leaf gas exchange process rates on a leaf area basis were not significantly affected despite the development of interveinal necrosis. However, calculated rates of whole-plant photosynthesis were associated with the observed negative impacts of pH 1.68 fog on vegetative growth. In contrast, plants grown in ambient O 3 (whole-study 12 hr average of 66 ppb) exhibited no significant alterations in growth, but yields were higher than in plants exposed to charcoal-filtered air. Exposure to ambient O 3 induced depressions in leaf gas exchange on a unit areas basis (i.e. net photosynthesis, stomatal conductance of water vapor, and transpiration), but calculated whole-plant photosynthesis was similar in charcoal-filtered air and O 3-exposed plants due to differences in leaf area per plant (i.e. 14% higher in O 3-exposed plants). It is concluded that acidic fog-induced alterations in strawberry growth were predicated upon the development of extensive foliar injury leading to the inhibition of whole-plant photosynthesis. However, in O 3-exposed plants, whole-plant photosynthetic rates were conserved, suggesting that impacts on assimilate partitioning may play a more prominent role.

Physiological responses of soybean (Glycine max L. Merr) to simulated acid rain and ambient ozone in the field

Physiological processes in field-grown soybean (Glycine max L. Merr. 'Davis’) to determine if plant responses were altered by simulated acid rain and if the responses to acid rain were modified by the presence of gaseous pollutants. Applications of simulated acid rain (pH 3.2, 4.2, and 5.2), alone or in combination with gaseous pollutants, did not significantly affect photosynthesis, transpiration, stomatal conductance of water vapor, or chlorophyll content at periodic intervals during the 1984 season. Furthermore, in leaf samples collected during pod fill, the concentrations of 11 elements were not significantly affected by simulated acid rain, alone or in combination with gaseous pollutants. These data are evidence that combinations of ambient rain and gaseous pollutants at similar levels may not cause significant physiological disruption in field-grown Davis soybean, and provide mechanistic support for studies where no significant effects on yield were reported.