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Abstract Detail



Physiological Section

Dowrey, Callie [1], Burns, Jean [2], Medeiros, Juliana [3].

Relationship of leaf anatomy and function to climate tolerance differs among evergreen, deciduous, and semi-evergreen Rhododendrons.

Rhododendrons are found in a large range of temperature habitats which may be facilitated by the evolution of a diversity of leaf habit. Members of the subgenus Pontica are evergreen, while those of subgenus Pentanthera are deciduous; but those in the subgenus Tsutsutsi are described as semi-deciduous, semi-evergreen, or “dimorphic”, where larger deciduous leaves grow in spring and smaller evergreen leaves in summer that over-winter. This intermediate leaf habit has not been well studied. We hypothesized that evergreen and deciduous leaves would be anatomically different with dimorphic leaves falling somewhere in between. We compared leaf and petiole anatomy of two species from habitats differing in mean annual temperature (MAT) from each subgenera: deciduous (R. austrinum and R. molle), evergreen (R. maximum and R. degronianum), and “dimorphic” (R. indicum and R.yedoense). We found that leaf size and specific leaf area (SLA) decreased significantly as MAT increased, but there were differences among the subgenera in how leaf anatomy changed across MAT. In addition, net photosynthesis, SLA, spongy mesophyll and epidermal area were all significantly higher for deciduous compared to evergreen plants. In contrast, leaf size and petiole Huber Value were significantly lower for deciduous compared to evergreens. When the species of subgenus Tsutsutsi were considered as a whole there was a trend toward intermediate values compared to the evergreen and deciduous leaves, supporting the hypothesis that the habits are on a spectrum between deciduous and evergreen. The dimorphic leaf habit varied a lot, however. For R. indicum the spring “deciduous” and summer “evergreen” leaves followed similar patterns as in deciduous and evergreen species. In contrast, R. yedoense leaves were overall more anatomically similar to deciduous species, and their spring and summer leaves showed few anatomical differences. We suggest that the differences in leaf and petiole anatomy contribute to the diversity of Rhododendron habitats. Deciduous leaves have traits associated with a warm, short growing season and ample sunlight. In contrast evergreen leaves have traits associated with a cooler, low-light habitat. Finally, our data suggest that the dimorphic species may be able to acclimate to a variety of different environments via trait plasticity.


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Related Links:
Website for Medeiros lab


1 - Indiana University, Biology, 12226 Castle Court, Carmel, IN, 46033, USA
2 - Case Western Reserve University, Biology, 2080 Adelbert Road RM#307 DeGrace Hall, Cleveland, OH, 44106, USA
3 - The Holden Arboretum, Ecology And Evolutionary Biology, 9500 Sperry Rd, Kirtland, OH, 44094, USA

Keywords:
Rhododendron
Leaf traits
leaf anatomy
dimorphic
semi-evergreen
semi-deciduous
temperature tolerance
azalea
plant physiology
specific leaf area
mesophyll.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Hall D/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 5:30 PM
Number: PPS005
Abstract ID:909
Candidate for Awards:Physiological Section Best poster presentation

Canceled

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