title: Physiological responses in two populations of Andropogon glomeratus Walter B.S.P. to short-term salinity.
abstract: Andropogon glomeratus is a C4nonhalophytic grass which exhibits population differentiation for tolerance to short-term salinity exposure. To investigate possible physiological mechanisms whch enable salt-tolerant individuals to survive short-term inundation, gas exchange and water relations parameters were measured before and during a 5-day watering treatment of half-strength synthetic seawater in plants from a tolerant and a non-tolerant population. Photosynthetic recovery was followed for 10 days after the salinity treatment. Photosynthetic CO2uptake was substantially inhibited in both populations. Stomatal conductances decreased and intercellular CO2concentrations increased, indicating non-stomatal factors were primarily responsible for the decrease in CO2uptake. After termination of the salinity treatment photosynthetic capacity increased more rapidly in the tolerant population and reached the pretreatment level after 6 days, whereas the nontolerant population did not recover fully after 10 days. A-Ci curves measured before and after the salinity treatment indicated a decrease in the carboxylation efficiency, and suggested a proportionately greater metabolic inhibition relative to the increase in the stomatal limitation. Osmotic adjustment occurred in a 2-day period in the tolerant population, but there was no change in the osmotic potentials or the water potential at the point of turgor loss in the nontolerant population. Thus short-term salt tolerance in the marsh population is associated with rapid osmotic adjustment and recovcry of photosynthetic capacity shortly after the end of the salinity exposure, rather than maintenance of greater photosynthesis during the salinity treatment.
authors.affiliation: Department of Botany, Duke University, 27706, Durham, NC, USA.
authors.forename: William D
authors.initials: WD
authors.lastname: Bowman
authors.affiliation: Department of Botany, Duke University, 27706, Durham, NC, USA.
authors.forename: Boyd R
authors.initials: BR
authors.lastname: Strain
keywords: A-Ci curves; Andropogon glomeratus; Osmotic adjustment; Photosynthesis; Salinity