Cottonwoods are poplar trees that are adapted to riparian zones that are naturally occasionally flooded. Like all Salicaceae, cottonwoods are dioecious and prior studies have indicated that males are more drought-tolerant than females and found more often in poorer, drier sites. We investigated sex differentiation of cottonwoods in response to the opposite water-stress, flood, and predicted that the increased water-stress tolerance of males in drought would also apply to flood-stress. Twenty-one clones of male and female narrowleaf cottonwoods (Populus angustifolia) were grown in a greenhouse along with three female clones of the hybrid native lanceleaf cottonwood (P. x acuminata) for comparison. It was anticipated that the hybrids would show the fastest growth owing to the genetic contribution from the P. deltoides parent and its rapid intrinsic growth rate.
Flood reduced heights and the numbers and sizes of leaves and roots, and consequently dry weights, abaxial stomatal conductance and leaf chlorophyll. Inundation increased carbon:nitrogen, but did not alter stomatal density, leaf water potential, or δ13C. The hybrid saplings were much larger than the narrowleaf saplings but their proportional growth reduction with flooding was greater than in the female P. angustifolia, suggesting higher flood-tolerance of the narrowleaf cottonwood. P. angustifolia sexes performed similarly under reference conditions but the males were proportionally more inhibited by flood, suggesting sex differentiation in flood-tolerance. This study indicates that riparian cottonwoods are reasonably flood-tolerant but slight differences exist between the sexes and to a greater extent, across taxa. While prior studies have indicated males are apparently more tolerant of drought, females are probably more flood-tolerant. / xiii, 117 leaves : ill. ; 29 cm
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:ALU.w.uleth.ca/dspace#10133/1291 |
| Date | January 2009 |
| Creators | Nielsen, Julie L., University of Lethbridge. Faculty of Arts and Science |
| Contributors | Rood, Stewart B. |
| Publisher | Lethbridge, Alta. : University of Lethbridge, Dept. of Biological Sciences, c2009, Arts and Science, Department of Biological Sciences |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
| Relation | Thesis (University of Lethbridge. Faculty of Arts and Science) |
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