Naumann, Julie , Young, Donald R , Anderson, John E .
Linking leaf optical properties to physiological responses for stress detection in coastal plant species.
EFFECTS of salinity and drought on photosynthesis, water relations, and chlorophyll fluorescence were used to evaluate stress in two coastal plants, Phragmites australis and Myrica cerifera. Drought and salinity stress were induced and physiological measurements (photosynthesis, stomatal conductance, xylem pressure potential, and leaf fluorescence) conducted for one week following treatment. Chlorophyll fluorescence was measured using two different methods: induction kinetics and steady-state fluorescence. Dark and light-adapted leaves were excited at 630nm and analyzed using a leaf chamber fluorometer (LICOR). Measurements of steady-state fluorescence were made with an Horiba Fluorolog luminescence spectrometer. Plants were excited with light at 460nm, and emission spectra evaluated between 625-800 nm. For both species, the onset of stress began at 2 ppt, as seen by significant decreases in water relations. Despite the physiological effects of salinity, there was no significant difference in maximum quantum efficiency (Fv/Fm) at any salinity level. Significant differences in Fv/Fm’, photochemical quenching, and steady-state fluorescence occurred at 10 ppt in M. cerifera. Drought studies showed similar results, with significant decreases in water relations occurring by day two in P. australis and day three in M. cerifera. Differences in light-adapted and steady-state fluorescence measurements were seen by day five for both species, while dark adapted fluorescence showed no indication of stress, even though visible signs were apparent (i.e., wilted leaves). These studies indicate that traditional dark-adapted fluorescence measurements may not be useful for determining environmental stress in all species. Light-adapted and steady-state fluorescence measurements appear more indicative of stress. This application of stress detection successfully provided an assessment of the physiological limits of optimal species performance with respect to specific environmental stresses. Remote detection of plant stress utilizing fluorescence techniques may be applicable for assessing the potential population expansion of species that form extensive monocultures. -DU
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1 - Virginia Commonwealth University, Department of Biology, P.O. Box 842012, Richmond, Virginia, 23284, USA
Presentation Type: Oral Paper:Papers for Topics
Location: 134/Performing Arts Center
Date: Monday, July 31st, 2006
Time: 10:30 AM