|CONSTABLE, JOHN - Fresno State University|
|STEBBINS, JOHN - Non ARS Employee|
|WINCHELL, CHRISTOPHER - H T Harvey & Associates|
Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/15/2014
Publication Date: 8/10/2014
Citation: Constable, J.V., Stebbins, J., Winchell, C., Wallis, C.M. 2014. Differences between Helianthus winteri and Helianthus annuus are deeper than physiology. Ecological Society of America Abstracts. PS 57-121.
Technical Abstract: Winter’s sunflower (Helianthus winteri, Hw), a new sunflower species, is found on rocky, un-grazed, south facing slopes of the Southern Sierra Nevada foothills between the valley edge and several hundred feet upslope. This study characterized physiological differences between Helianthus winteri (Hw) and Helianthus annuus (Ha), a common species on the valley floor, to identify potential mechanisms that contribute to habitat preferences. Seed mass, stem caliper diameter, stomatal characteristics, and photosynthetic capacity of both species were measured. Leaf and flower samples were collected from plants grown in a well-watered common garden, pulverized, and extracted in either methanol, to examine phenolics by high performance liquid chromatography, or hexane, to examine terpenoids by gas chromatography. Seed mass of Hw was significantly greater than Ha. Stem caliper diameter and stomatal characteristics did not differ between species. However, Hw had lower specific leaf area than Ha. Photosynthetic capacity, as measured by gas exchange, of young fully expanded leaves did not differ between the species. Total phenolic content of flowers and leaves was marginally greater in Hw than Ha. Hw and Ha possessed similar floral total monoterpene content and profile, but Hw leaf monoterpene content exceeded those in Ha. There were significant differences in the concentration of specific phenolics and terpenoid species. Differences in habitat initially suggested that Hw might exhibit more drought-tolerant characteristics relative to Ha. This interpretation is supported by specific leaf area differences, but is not corroborated by other measurements. As this study used plants from a well-watered common garden, it is probable that physiological differences might be amplified in the field where environment by genotype interactions are more profound.