PARENT SESSION
Poster Session 7: Invasive Species.
Monday, August 2 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.
Variability in photosynthetic gas exchange characteristics between life-stages and tissue types of Centaurea maculosa.
Hill, Judson*,1, Germino, Matthew1, 1 Idaho State University, Pocatello, ID
ABSTRACT- Adaptive variations in plant form and function can benefit the fitness of a species by maximizing its carbon assimilation (Anet) in multiple environments. Invasive species that proliferate in many environments are often characterized by rapid growth rates. One of the most successful invasive species in the western U.S. is Centaurea maculosa (European Spotted Knapweed). C. maculosa has two life stages: seedlings that only have basal rosette leaves, and mature plants that have three different types of photosynthetic tissues including basal rosette leaves, photosynthetic stems, and cauline leaves. The purpose of this research was to determine if ecophysiological characteristics differed between these life-stages as a function of their different photosynthetic tissues. Gas exchange measurements were made on each of the morphotypes and tissue types of two populations of C. maculosa in SW Montana that differed in their available soil water, during two years that differed in their seasonal precipitation. Anet of basal rosette leaves was similar for seedlings and adults. Anet and water use efficiency (WUE) was greater in cauline compared to rosette leaves and stems, except under water limitation, when WUE of stems and rosette leaves increased. Also, when seasonal drought stress led to senescence of rosette leaves in August 2003, the stems and cauline leaves remained photosynthetically active. Greater Anet and increased WUE of cauline leaves corresponds with their relatively greater presence during the drier half of the summers, when the long and prolific season for seed output of C. maculosa occurs. Our data suggests that multiple types of photosynthetically active tissue on C. maculosa enables continued carbon assimilation throughout the growth season, thus increasing its ecological success across multiple habitats.
Key words: multiple tissue types, carbon assimilation, Centaurea maculosa, gas exchange