Abstract Detail

Ecophysiology

Mocko, Kerri [1], Jones, Cynthia [2].

Physiological responses to drought reflect phylogenetic history in South African Pelargoniums (Geraniaceae).

Pelargonium is a speciose and morphologically diverse genus of plants. The group is monophyletic, predominantly South African, and it has an interesting history of diversification. Two major clades comprising ~90% of species of the genus demonstrate equally remarkable variation in growth form yet are presumed to have diversified under different climates in the history of South Africa: clade C under wet, mesic-subtropical conditions and clade A in response to increasing aridification and pronounced seasonality. We ask: do physiologies in the two clades reflect historical adaptations to paleoclimates, or have growth forms in both clades adopted unique functional strategies independently of phylogeny? To test these hypotheses, we imposed an experimental drought in the greenhouse on 6 clade A and 6 clade C species paired for 3 different growth forms. We found significantly different patterns of change in water potential and stomatal conductance across species, with species demonstrating a full spectrum of responses from extreme isohydric to anisohydric behaviors. Response to drought contrasted significantly at the clade level, as clade A species were more anisohydric and clade C species more isohydric; growth forms across clades occupied more of a continuum. We propose that isohydry may be advantageous with high evaporative demand and a long growing season, while anisohydry may have evolved as a highly adaptive strategy under winter rainfall conditions when leaves function during the cool, rainy season. Physiological responses to drought in this genus are consistent with the climate of origin hypothesis; these strategies have been conserved in the major clades, irrespective of growth form.

Broader Impacts:

1 - University of Connecticut, Ecology And Evolutionary Biology, U-3043, 75 N. Eagleville Rd, Storrs, CT, 06269, USA
2 - University of Connecticut, Department of Ecology & Evolutionary Biology, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA

Keywords:
South Africa
stomatal conductance
photosynthesis
water potential
experimental drought
isohydric
anisohydric.

Presentation Type: Oral Paper:Papers for Topics
Session: 27
Location: Elmwood/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 10:45 AM
Number: 27003
Abstract ID:302
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize