Gordon, Elizabeth , Lewis, James , Tissue, David .
Potential regulatory mechanisms that control photosynthetic responses to developmental processes in Xanthium strumarium.
Photosynthetic adjustments to developmental changes such as flowering as well as age-related changes in morphology are frequently attributed to a source:sink feedback mechanism. This mechanism may be driven by changes in soluble sugars within the leaf that induce changes in the activity of key enzymes that regulate photosynthesis. The objective of our study was to develop a detailed, quantitative understanding of the roles of specific soluble sugars in regulating photosynthetic responses to specific developmental events. In this study, we manipulated sink activity by manipulating N and P supply, and we manipulated source:sink balance by manipulating plant age at flowering. We planted seeds of Xanthium strumarium, a determinate short-day plant, at 10-day intervals to generate three different aged cohorts and exposed these plants to variable N and P supplies. At 45 days after initial seedling emergence, flowering was induced in all plants by exposing plants to a short-day (12 h photoperiod). Preliminary data indicates that reduced sink strength due to the onset of flowering and decreased nutrient supply resulted in reduced net photosynthesis and photosynthetic capacity (Amax, Vcmax, Jmax), increased soluble sugar and starch accumulation, and significant reductions in sucrose phosphate synthase (SPS) activity, but no significant changes in invertase activity. The physiological and biochemical changes associated with the onset of flowering increased as sink activity decreased due to decreased nutrient supply and increasing plant age. Our results suggest that photosynthetic responses to flowering are driven by an enzyme-level source:sink feedback mechanism associated with changes in SPS activity, but not changes in invertase activity.
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1 - Texas Tech University, Biological Sciences, P.O. Box 43131, Lubbock, TX, 79409, USA
2 - Fordham University, Biology
3 - Texas Tech University, Biological Sciences
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM