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Interactions between parental plant light environment and reproductive architecture in Polygonum hydropiper.
Lundgren, Marjorie*,1, Sultan, Sonia2, 1 Wesleyan University, Middletown, CT2 Wesleyan University, Middletown, CT
ABSTRACT- Polygonum hydropiper (Polygonaceae) is an annual, introduced species of moist, open habitats. Interestingly, plants of this species produce two distinct reproductive architectures: a long terminal raceme and an inconspicuous, small axial inflorescence. We hypothesized that cross-generational effects of environmental stresses such as low light might differently affect these distinct inflorescence types. Specifically, we predicted that light-stressed parental plants would preferentially allocate resources to the more efficiently dispersed terminal inflorescences. We grew inbred full-sib parents from cross generational lines of two natural populations in full sunlight and simulated shade (24 % full sun and R:FR ratio of 0.8), and measured the initial mass, germination, and seedling growth traits of their terminal and axial achenes under uniform growth chamber conditions. The effects of parental light environment differed significantly in these terminal and axial reproductive structures. For example, parental light treatment significantly affected axial achenes, which had reduced mass in low light, while in contrast the mass of terminal achenes was constant across light environments. Although the parent light environment did not significantly influence seedlings from axial achenes, those from terminal achenes showed significantly enhanced growth traits, including seedling height, timing of leaf development, leaf number, and biomass, as a result of parental light deprivation. In shaded conditions where resources are limiting, P. hydropiper prioritizes terminal achenes. This may be because P. hydropiper plants produce far more terminal than axial achenes, making terminal achenes a stronger resource sink. Additionally, terminal achenes are likely to disperse further from the parent plant, and may contribute more to fitness than achenes dispersed to the shaded parental site.
Key words: Polygonum hydropiper, parental effects, reproductive architecture, light availability