Cortes-Palomec, Aurea C. , Ballard, H. E. , Brown, Kim J. .
Comparing the flowering phenologies of a tropical (Viola grahamii) and a temperate violet (Viola striata) (Violaceae).
The production of both cleistogamous as well as chasmogamous flowers by an individual is a phenomenon that occurs in ca. 56 families and 287 species of flowering plants. The genus Viola (Violaceae) is a classic example where this mixed reproductive strategy is present. Even though both floral types are present in the same individual, they are not equally expressed temporally in most temperate forest species. These differences are suggested to be mediated by changes in photoperiod, with chasmogamous flowers produced in shorter days and cleistogamous flowers produced in longer days. However, there are no studies referring to flowering in tropical species of Viola where photoperiod does not change as dramatically as in temperate forests.
For this study two perennial species of contrasting habitats were chosen to evaluate the breeding system of Viola: the tropical Viola grahamii Bentham (having wide distribution in Central Mexico) and V. striata Aiton (common in temperate woods in the northern and eastern United States and Canada). Viola striata populations were studied in southern Ohio, USA, and V. grahamii populations were studied in the mountainous areas surrounding Lake Pátzcuaro in the state of Michoacán, Mexico. Studies were conducted in 2002 and 2003. For each species, 40 semi-permanent quadrats were randomly established and phenological observations of blooming times during two growing seasons for the two species were recorded, along with soil properties (N, K, P, Ca, Mg, pH, and moisture), light availability, and photoperiod. The temperate violet, V. striata, showed differences in the peaks of blooming for the two flower types. In contrast the tropical violet, V. grahamii, produced the two flower types at the same time. Further discussion of the effects of environment on reproduction will be presented.
1 - Ohio University, Department of Environmental and Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
Presentation Type: Paper
Location: Wasatch (Cliff Lodge)
Date: Tuesday, August 3rd, 2004
Time: 3:00 PM