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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCED MIDWESTERN CROPPING SYSTEMS FOR SUSTAINABILITY AND ENVIRONMENTAL QUALITY Title: Seasonal Changes in Photosynthesis, Antioxidant Systems and ELIP Expression in a Thermonastic and Non-thermonastic Rhododendron Species: A Comparison of Photoprotective Strategies in Overwintering Plants

Authors
item Wang, X -
item Peng, Y -
item Singer, Jeremy
item Fessehaie, A -
item Krebs, S -
item Arora, R -

Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 17, 2009
Publication Date: October 12, 2009
Citation: Wang, X., Peng, Y., Singer, J.W., Fessehaie, A., Krebs, S.L., Arora, R. 2009. Seasonal Changes in Photosynthesis, Antioxidant Systems and ELIP Expression in a Thermonastic and Non-thermonastic Rhododendron Species: A Comparison of Photoprotective Strategies in Overwintering Plants. Plant Science. 177:607-617.

Interpretive Summary: Leaves of overwintering evergreen rhododendrons are typically exposed to freezing temperatures and high light during winters which can potentially result in photon flux exceeding that required for photochemistry. This excess energy, if not dissipated as heat or fluorescence, may cause photo-oxidative damage. The goal of this study was to compare the photoprotection strategies during seasonal cold acclimation in two rhododendron species that are divergent in their leaf freezing tolerance and temperature-induced leaf movement. During seasonal cold acclimation, maximum photosynthetic rate and maximum quantum efficiency were significantly down-regulated. The two species respond differently to winter conditions and have evolved strategies to avoid, reduce or tolerate photooxidative stress in winter. Results from this study may lead to improved genotypic and phenotypic selection for commercial rhododendron releases.

Technical Abstract: Leaves of overwintering evergreen rhododendrons are typically exposed to freezing temperatures and high light during winters which can potentially result in photon flux exceeding that required for photochemistry. This excess energy, if not dissipated as heat or fluorescence, may cause photo-oxidative damage to PSII. The goal of this study was to compare the photoprotection strategies during seasonal cold acclimation (CA) in two Rhododendron species (R. catawbiense Michx. and R. ponticum L.) that are divergent in their leaf freezing tolerance and thermonastic behaviour (temperature-induced leaf movement). Differences in leaf freezing tolerance (LT50), photosynthesis, photoinhibition, early light-induced proteins (ELIPs) gene expression, and accumulation of antioxidant metabolites and enzymes during seasonal CA were investigated. During seasonal CA, maximum photosynthetic rate (Pmax) and maximum quantum efficiency of PSII (Fv/Fm) were significantly down-regulated. Compared with R. catawbiense, R. ponticum showed less photoinhibition and higher accumulation of antioxidant systems while R. catawbiense exhibited more efficient up-regulation of ELIP expression and antioxidant system. The two species respond differently to winter conditions and have evolved strategies to avoid, reduce and/or tolerate photooxidative stress in winter. These include down-regulation of photosynthesis and up-regulation of ELIPs and antioxidant systems, together with specialized leaf anatomy and thermonasty behaviour.

Last Modified: 4/19/2014