McDonald, Brienna , Gehring, Janet .
A comparative study of the response of two Helianthus species to water availability.
Differences in the local distribution of congeners can result from adaptation to biotic and abiotic factors in their respective habitats. We studied two species of sunflowers, Helianthus grosseserratus and H.occidentalis that grow in different environments. Helianthus occidentalis is found in dry, open environments such as sand and hill prairies whereas H. grosseserratus is typically found in areas with higher moisture availability. We hypothesized functional traits related to drought tolerance would differ between the two Helianthus species and coincide with their typical habitats. We also hypothesized phenotypic plasticity would differ between the two species in response to water availability. To test our hypotheses, we exposed individuals of both species to three levels of water availability. Relative water content (RWC) at harvest indicated our experimental treatments were effective; relative water content was highest in high-water plants and decreased with water availability. Our results show that H. grosseserratus grew faster and larger than H. occidentalis, even under low water conditions. Helianthus grosseserratus was largest in high-water conditions whereas H. occidentalis gained the most biomass in the medium water treatment. Specific leaf area (SLA) of H. occidentalis was lower than in H. grosseserratus, suggesting H. occidentalis leaves are thicker and may have higher water-use-efficiency. Furthermore, H. occidentalis adjusted its SLA in response to water availability to a much greater extent than did H. grosseserratus, which may have contributed to the ability of H. occidentalis to maintain RWC. We conclude that H. occidentalis is restricted to dry open environments both because it is adapted to dry conditions but also because it may be excluded from high-water habitats.
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specific leaf area
relative water content
Presentation Type: Poster:Posters for Sections
Location: Khorassan Ballroom/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 5:30 PM