Abstract Detail

Ecophysiology

Pilote, Alex [1], Donovan, Lisa [1].

Drought effects on hydraulic anatomy of six Helianthus species, varying in source-site water availability.

Xylem structure is central to the plant-water balance, and thus is of great importance in tolerance to water limitation. Under low-water availability, plants must be able to resist drought-induced cavitation to maintain adequate supply of water to leaves. This is often achieved via reinforcement of cell walls and reduction of the proportion of large conduits in newly produced xylem; the governing processes of which have been shown to be species-specific. Most studies to date have focused on perennial, woody species in inter-annual experiments, making it difficult to conclude the role that xylem structural acclimation plays in determining productivity under water limitation. This experiment involved growing six Helianthus species under well-watered and water-limited conditions, and assessing differences between species pairs (three pairs of species, one from a mesic habitat and one from a xeric habitat) to infer whether species differ in their ability to alter xylem structure and/or maintain high productivity under water-limiting conditions. Hydraulic anatomy was analyzed via stem cross-sections, with vessel and fiber cell properties measured with imaging software. Gas exchange, biomass allocation, and leaf anatomical traits were further assessed for cross-species and treatment comparison. The effects of water limitation on the hydraulic anatomy, leaf function and anatomy, and overall productivity of these species were assessed between species pairs to reduce phylogenetic bias (the three pairs were chosen from across the phylogeny). Thus results are based on majority trends across three pairs (two annual and one perennial pairs). Water limitation resulted in reduced xylem lumen fraction, reduced hydraulically weighted mean vessel size, increased resistance to implosion, and increased vessel density. This treatment further resulted in decreased gas exchange and increased water use efficiency and root-mass-ratio. When comparing mesic and xeric species pairs, the species from more-xeric habitats experienced greater alterations to both hydraulic parameters and overall biomass production. This suggests that these xeric species are more potentially more plastic in their hydraulic anatomy, but that this plasticity is not resulting in an adaptive advantage under water limitation. This may be due to the ecological strategies of these herbaceous species, which may mature quickly in xeric environments to avoid water-limiting conditions, and thus avoid growth under the extreme environments representative of their source sites.

1 - University of Georgia, Plant Biology, 2502 Miller Plant Sciences, University of Georgia, Athens, GA, 30602, United States

Keywords:
drought
xylem
Helianthus.

Presentation Type: Poster
Session: P, Ecophysiology Poster Session
Location: Exhibit Hall/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PEP010
Abstract ID:626
Candidate for Awards:Physiological Section Best poster presentation,Physiological Section Physiological Section Li-COR Prize