Browsing by Subject "senescence"

Now showing 1 - 3 of 3
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    Coordination of Phloem Function and Anthocyanin Accumulation in Senescing Leaves of Quercus rubra
    (2023-11) Rooney, Rebecca
    Autumnal senescence is an important annual occurrence for many deciduous temperate species, as it is the final period for plants to regain limiting nutrients from leaf tissue. Effective remobilization requires efficient breakdown of cellular components and translocation into perennating tissues via the phloem, a vascular tissue primarily responsible for the transport of photoassimilates. Anthocyanins are a pigment that accumulate in some species during senescence and are hypothesized to confer a photoprotective role in senescing leaves. Anthocyanin biosynthesis is regulated, in part, by sugar signaling, and girdling studies have linked phloem to anthocyanin accumulation to the augmentation of sugar concentrations in leaf tissue. While these studies show that halted translocation is associated with anthocyanin biosynthesis, natural changes in the phloem during autumnal senescence have yet to be examined with respect to anthocyanin. Here I elucidate how changes in phloem function (e.g., leaf carbon export and callose deposition) corresponds to soluble sugars and anthocyanin buildup in leaf tissue during senescence. I found that while phloem function declined throughout senescence, soluble sugars did not accumulate in leaf tissue. Despite this, anthocyanin content did significantly increase by the end of the season. Carbon export did not correlate to anthocyanin buildup or callose deposition. Instead, carbon export corresponded to changes in the proportions of leaf soluble sugars, while anthocyanic leaves were associated with higher fructose concentrations. My results indicate that soluble sugars are involved in multiple processes in senescing leaves and their relationship to anthocyanin and phloem is nuanced. This study provides insight into how phloem function declines during senescence, while prompting further studies into the regulation of phloem transport and how changes in this system may impact other leaf functions during autumnal senescence.
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    Maximum carbon assimilation model for understory wood plants growing at Bagley Nature Area in Duluth, MN
    (2020-05-26) O'Connell, Erin M; Savage, Jessica A; oconn877@d.umn.edu; O'Connell, Erin M; Savage research team
    These data were collected and analyzed for a project comparing the leaf phenology, carbon gain, growth, and freezing susceptibility of invasive and native species. Maximum seasonal carbon assimilation was modeled for six plants per eight species growing in a 50-year-old mixed forest. The model is based on understory light availability on sunny days, carbon dioxide assimilation rates, and leaf area adjusted in the spring for expanding leaves and in the fall for senescing leaves.
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    Plant phenology, growth, freezing damage, and carbon gain data observed from 2017 to 2018 on wood plants growing at Bagley Nature Area in Duluth, MN
    (2020-05-26) O'Connell, Erin M; Savage, Jessica A; oconn877@d.umn.edu; O'Connell, Erin M; Savage research team
    These data were collected for a project comparing the leaf phenology, carbon gain, growth, and freezing susceptibility of four invasive and four native species. Leaf phenology and stem growth were observed for ten individuals per understory wood shrubs species. Freezing damage was experimentally assessed for each species and minimum temperatures in the species' native and exotic ranges were determined. Carbon gain was modeled for six individuals per species based on photosynthetic light response curves, leaf phenology, and understory light.