Colorado mountains
From Long-Term Data to Understanding: Toward a Predictive Ecology
2015 LTER ASM Estes Park, CO - August 30 - September 2, 2015

Seasonal variation in xanthophyll-cycle pigments among species with contrasting water use strategies

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Shan Kothari
Jeannine Cavender-Bares
Amy Verhoeven
Keren Bitan
Rebecca Montgomery
John Gamon

Drought is a powerful limitation on photosynthetic rates in plants, as it may force plants to close their stomata at the risk of severe water loss. Xanthophylls and other pigments play a crucial role in helping plants cope with drought stress through means such as non-photochemical quenching (NPQ). Laboratory and field experiments have demonstrated that plant species may differentially upregulate these pigments in response to stress. Because plants with high water-use efficiency, such as C4 plants, may maintain photosynthesis even during drought, we expect them to show weaker upregulation of xanthophylls involved in NPQ when water availability is low. At multiple time points in summer 2014, we measured pigment concentrations, water use efficiency, chlorophyll fluorescence, and visible-region leaf reflectance spectra for fifteen prairie species at Cedar Creek LTER. Families and species tended to differ strongly in their pigment concentrations and xanthophyll de-epoxidation states. We found significant changes in pigment concentrations and de-epoxidation states across the season, which tended to be more intense in species with low water-use efficiency. We also found that temporal changes in pigment concentrations are reflected by changes in Photochemical Reflectance Index (PRI), a spectral measure of light-use efficiency, demonstrating that phenological or stress-induced changes in pigment concentrations affect the spectral signatures of plants.

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