Laird, Robert

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https://opus.uleth.ca/handle/10133/3960

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Browsing Laird, Robert by Subject "Duckweed"

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    Caloric restriction extends lifespan in a clonal plant
    (Wiley, 2024) Chmilar, Suzanne L.; Luzardo, Amanda C.; Dutt, Priyanka; Pawluck, Abbe; Thwaites, Victoria C.; Laird, Robert
    When subjected to dietary caloric restriction (CR), individual animals often outlive well-fed conspecifics. Here, we address whether CR also extends lifespan in plants. Whereas caloric intake in animals comes from ingestion, in plants it derives from photosynthesis. Thus, factors that reduce photosynthesis, such as reduced light intensity, can induce CR. In two lab experiments investigating the aquatic macrophyte Lemna minor, we tracked hundreds of individuals longitudinally, with light intensity—and hence, CR—manipulated using neutral-density filters. In both experiments, CR dramatically increased lifespan through a process of temporal scaling. Moreover, the magnitude of lifespan extension accorded with the assumptions that (a) light intensity positively relates to photosynthesis following Michaelis–Menten kinetics, and (b) photosynthesis negatively relates to lifespan via a power law. Our results emphasize that CR-mediated lifespan extension applies to autotrophs as well as heterotrophs, and suggest that variation in light intensity has quantitatively predictable effects on plant aging trajectories.
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    A multigenerational effect of parental age on offspring size but not fitness in common duckweed (Lemna minor)
    (2016-06-15) Barks, Patrick M.; Laird, Robert A.
    Classic theories on the evolution of senescence make the simplifying assumption that all offspring are of equal quality, so that demographic senescence only manifests through declining rates of survival or fecundity. However, there is now evidence that, in addition to declining rates of survival and fecundity, many organisms are subject to age-related declines in the quality of offspring produced (i.e. parental age effects). Recent modelling approaches allow for the incorporation of parental age effects into classic demographic analyses, assuming that such effects are limited to a single generation. Does this ‘single generation’ assumption hold? To find out, we conducted a laboratory study with the aquatic plant Lemna minor, a species for which parental age effects have been demonstrated previously. We compared the size and fitness of 423 lab-cultured plants (asexually-derived ramets) representing various birth orders, and ancestral ‘birth-order genealogies’. We found that offspring size and fitness both declined with increasing ‘immediate’ birth order (i.e. birth order with respect to the immediate parent), but only offspring size was affected by ancestral birth order. Thus, the assumption that parental age effects on offspring fitness are limited to a single generation does in fact hold for L. minor. This result will guide theorists aiming to refine and generalise modelling approaches that incorporate parental age effects into evolutionary theory on senescence.