Browsing by Subject "seed size"

Now showing 1 - 4 of 4
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    Complete Data and Analysis for: Effects of seed traits and dormancy break treatments on germination of four aquatic plant species
    (2023-06-29) Verhoeven, Michael R; Bacon, Jonah A; Larkin, Daniel J; michael.verhoeven.mrv@gmail.com; Verhoeven, Michael; Minnesota Aquatic Invasive Species Research Center (MAISRC)
    This repository contains the raw data and code necessary to conduct the analyses in the companion paper.
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    Functional traits and the growth-mortality tradeoff in tropical trees
    (Ecological Society of America, 2010) Wright, S Joseph; Kitajima, Kaoru; Kraft, Nathan J B; Reich, Peter B; Wright, Ian J; Bunker, Daniel E; Condit, Richard; Dalling, James W; Davies, Stuart J; Diaz, Sandra; Engelbrecht, Bettina M J; Harms, Kyle E; Hubbell, Stephen P; Marks, Christian O; Ruiz-Jaen, Maria C; Salvador, Cristina M; Zanne, Amy E
    A trade-off between growth and mortality rates characterizes tree species in closed canopy forests. This trade-off is maintained by inherent differences among species and spatial variation in light availability caused by canopy-opening disturbances. We evaluated conditions under which the trade-off is expressed and relationships with four key functional traits for 103 tree species from Barro Colorado Island, Panama. The trade-off is strongest for saplings for growth rates of the fastest growing individuals and mortality rates of the slowest growing individuals (r2 = 0.69), intermediate for saplings for average growth rates and overall mortality rates (r2 = 0.46), and much weaker for large trees (r2 ≤ 0.10). This parallels likely levels of spatial variation in light availability, which is greatest for fast- vs. slow-growing saplings and least for large trees with foliage in the forest canopy. Inherent attributes of species contributing to the trade-off include abilities to disperse, acquire resources, grow rapidly, and tolerate shade and other stresses. There is growing interest in the possibility that functional traits might provide insight into such ecological differences and a growing consensus that seed mass (SM), leaf mass per area (LMA), wood density (WD), and maximum height (Hmax) are key traits among forest trees. Seed mass, LMA, WD, and Hmax are predicted to be small for light-demanding species with rapid growth and mortality and large for shade-tolerant species with slow growth and mortality. Six of these trait–demographic rate predictions were realized for saplings; however, with the exception of WD, the relationships were weak (r2 < 0.1 for three and r2 < 0.2 for five of the six remaining relationships). The four traits together explained 43–44% of interspecific variation in species positions on the growth–mortality trade-off; however, WD alone accounted for >80% of the explained variation and, after WD was included, LMA and Hmax made insignificant contributions. Virtually the full range of values of SM, LMA, and Hmax occurred at all positions on the growth–mortality trade-off. Although WD provides a promising start, a successful trait-based ecology of tropical forest trees will require consideration of additional traits.
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    Seed size, nitrogen supply, and growth rate affect tree seedling survival in deep shade
    (Ecological Society of America, 2000) Walters, Michael B; Reich, Peter B
    Species differences in seedling survival in deeply shaded understories (i.e., shade tolerance) may depend on both seed size and growth rates, but their relative contributions to survival and how they change with time and with variation in light and belowground resource availability is unknown. With a greenhouse experiment we investigated these relationships by examining responses of growth, growth-related morphology, survival, and their interrelationships to a range of nitrogen (3.4 × 10−9–3.4 × 10−3 mol/L N fertilizer solutions) and low light (0.6–7.3% of open sky) availabilities for young seedlings of 10 North American tree species that vary in observational shade tolerance rankings and seed size (Populus tremuloides, Betula papyrifera, Betula alleghaniensis, Acer saccharum, Larix laricina, Pinus banksiana, Pinus resinosa, Pinus strobus, Picea mariana, and Abies balsamea). Within all species, relative growth rate (RGR) and survival increased with light. RGR and survival also increased with N supply but only at the two highest light levels, and then only for the shade-intolerant, broad-leaved Populus and Betula spp.. In every species, survival was positively related to RGR. Moreover, each species differed in the relationship of survival to RGR, and these differences were related to seed mass: at any given RGR, large-seeded, shade-tolerant species had higher survival than smaller-seeded, intolerant ones. Across species, in most light and N treatments, seed mass was positively related to young seedling survival, but RGR was not. In very low light the relative benefits of greater seed mass to survival were temporary. As seedlings aged, interspecific mortality rates became more dependent on observational shade tolerance rankings than on seed size, but mortality was still unrelated to RGR. Our results indicate potentially important interactions among light, N, and species that could influence regeneration dynamics. For young seedlings in deeply shaded microsites, N supply does not matter, and only shade-tolerant species survive due, in part, to large seeds and physiological traits other than RGR. In moderate shade, RGR is greater, and survival is high for all species, except that small-seeded, broad-leaved, intolerant species have low survival and RGR at low N supply. This suggests that broad-leaved shade-intolerant species compete more effectively in moderate shade on richer soils than on poorer soils. Although we found that both seed mass and vegetative physiology influenced survival in shade, they did not covary tightly, suggesting that they are under somewhat separate selection pressures.
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    Understanding the genetic architecture of secondary domestication traits in Field Pennycress (Thlaspi arvense L.)
    (2022-12) Tandukar, Zenith
    Thlaspi arvense L. (Field Pennycress) is a newly domesticated winter annual oilseed capable of improving ecosystems and intensifying agricultural productivity without new land displacement. Pennycress is a winter hardy cover crop that provides ecosystem services such as reduced soil erosion and nutrient loss in between fall corn harvest and spring soybean planting. However, pennycress is currently limited by its small seed size and unimproved oil production. This dissertation builds on the limited research on pennycress breeding and genetics and aims to establish and characterize a global diversity panel of wild pennycress accessions, two biparental recombinant inbred populations, and three independent EMS-derived mutants to contribute knowledge and resources to understand important seed and agronomic characteristic traits in pennycress. Chapter 1 presents a literature review focused on the status of pennycress breeding and genetics, as well as factors that may shed light to understanding the genetic and physiological control of seed size and oil content. Chapter 2 presents a genetic dissection of seed size, oil content, and protein content via genome-wide association studies in a diversity panel. Chapter 3 explores and characterizes the phenotypic and genotypic diversity in two recombinant inbred populations developed for field pennycress, whereas chapter 4 reports the characterization of three independent wax mutants in pennycress and the implications of waxes on total seed oil content in pennycress.