Brouillette, Larry , Donovan, Lisa .
Variation in relative growth rate and its nitrogen-use components in Helianthus.
We examined relative growth rate and its nitrogen-use components in the Helianthus hybrid system to explore the nutrient stress response of the hybrid sunflower H. anomalus. The active sand dune habitat of H. anomalus contains lower levels of soil nutrients than the habitats of the parental species H. annuus and H. petiolaris. Therefore, we expected the hybrid species to have a lower maximum relative growth rate measured under non-limiting nitrogen levels as a consequence of a growth strategy that conserves nitrogen. When grown under limiting nitrogen, we expected to see the hybrid species growth rate decrease less than the growth rate of its parental species. All three species were grown in a glasshouse experiment with two treatments: non-limiting and limiting nitrogen. Plants were destructively harvested at four timepoints: 1, 3, 6, and 20 weeks after treatment initiation. As expected, H. anomalus had a lower early seedling maximum relative growth rate than the parental species. Additionally, we found that the growth rate of H. anomalus was less affected by nitrogen limitation than its parental species. Nitrogen productivity of the low-nitrogen H. anomalus plants was highest, indicating that the plants were able to produce more biomass per unit nitrogen than the other plants in the study. Higher nitrogen productivity appears to be mediated through a longer leaf lifespan, higher photosynthetic rate, and greater allocation of nitrogen to leaves by H. anomalus compared to its parental species. Future studies will examine the variability of these key traits in populations across the range of H. anomalus.
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1 - University of Georgia, Department of Plant Biology, 2502 Miller Plant Sciences Building, Athens, GA, 30602, USA
2 - University of Georgia, Department of Plant Biology, 2052 Miller Plant Sciences Building, Athens, Georgia, 30602-7271, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 28th, 2008
Time: 1:45 PM