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(Pezeshki et al. 1987) Pezeshki et al. (1987) investigated the response of a high marsh plant species to increases in salinity and found that even this halophytic plant experienced metabolic consequences to a saline environment. They also found evidence of a potential response to the osmoregulation problems imposed by saline soils. Treatments of high, low, and no (control) salt solutions were applied to individual plants in a greenhouse. Photosynthetic photon flux density, air temperature, relative humidity, and leaf temperature were measured every three hours for several days. Stomatal conductance and net photosynthesis were also calculated using a LI-COR model 3100. In addition, at selected intervals, leaf water potential was measured using a pressure chamber on one leaf per plant. Osmotic Effects Table 1 shows increasingly negative leaf water potentials in the low and high salinity treatment groups (Pezeshki et al. 1987). This is likely a consequence of the higher foliage Na+ concentrations in the salinity treatments. Lower leaf water potentials might help rectify problems with water uptake by increasing the water potential gradient from soil to leaf. These data suggest salt accumulation as a potential mechanism of salinity tolerance in Spartina patens (Pezeshki et al. 1987). Table 1: Mean stomatal conductance, net
photosynthesis, and water potential for salinity treatments and control
group (after Pezeshki et al. 1987).
Physiological Response Patterns in physiological response demonstrate additional negative effects of saline. Stomatal conductance and photosynthesis were higher for the control plants throughout the day (Figures 1 and 2). In contrast, both low and high salinity plants experienced reduced stomatal conductance and photosynthesis in comparison to the control group.
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