Abstract Detail

Physiology & Ecophysiology

Kothari, Shan [1], Cavender-Bares, Jeannine [2], Bitan, Keren [3], Verhoeven, Amy [4], Wang, Ran [5], Montgomery, Rebecca [6], Gamon, John [7].

Two Ways to Survive Light Stress in Prairie Plants.

When plants absorb light in excess of what they can use for photochemistry, they may be subject to oxidative damage, which causes photosynthetic stress. This condition is compounded by conditions that limit photochemistry, like drought. Photoprotective pigments, such as those involved in the xanthophyll cycle, can help plants withstand the stress of oxidative damage by dissipating excess light energy as heat. In this study, we aimed to characterize a spectrum of strategies used to cope with light stress by a diverse selection of 16 prairie species at Cedar Creek Ecosystem Science Reserve (East Bethel, MN). At multiple points throughout a single growing season, we measured photosynthetic and photoprotective pigment concentrations, gas exchange and chlorophyll fluorescence parameters, and leaf-level and canopy hyperspectral reflectance.
We find that across species and through time, concentrations of photosynthetic and photoprotective pigments are correlated with one another and phylogenetically conserved. During a mid-season period of water limitation, leaf-level physiology remained largely unchanged, with few clear indications of stress. However, at the canopy scale, plots dominated by species with constitutively low pigment concentrations showed a greater decline in mean reflectance. This change is most plausibly explained by alterations of canopy structure that reduce the horizontal projection of leaf area among species that have low concentrations of photoprotective pigments. Our findings suggest a spectrum defined by two contrasting strategies for withstanding light stress: (1) Using photoprotective pigments to dissipate excess energy, and (2) altering canopy structure to minimize interception of excess radiation. Finally, we conclude that reflectance-based indicators of photoprotective pigment activity may be unreliable indicators of light-use efficiency when canopy structure is variable.

1 - 1429 Cleveland Ave N. #2, St. Paul, MN, 55108, United States
2 - University Of Minnesota, 100 ECOLOGY BLDG, 1479 Gortner Ave, Saint Paul, MN, 55108, United States
3 - University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Ave., St. Paul, Minnesota, 55108, United States
4 - University of St. Thomas, Biology, 2115 Summit Ave, St. Paul, MN, 55105, USA
5 - University of Alberta, Earth and Atmospheric Sciences, 1-26 Earth Sciences Building, Edmonton, AB, T6G 2E9, Canada
6 - 1530 Cleveland Ave N., Green Hall 115, St. Paul, MN, 55108, United States
7 - University of Nebraska, Center for Advanced Land Management Information Technologies, 3310 Holdrege St., Lincoln, NE, 68583, USA

xanthophyll cycle
photochemical reflectance index
drought response
light-use efficiency
canopy architecture
trait covariance
trait conservatism
chlorophyll fluorescence
tallgrass prairies.

Presentation Type: Oral Paper
Abstract ID:108
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize,Physiological Section Best Paper Presentation

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