Author
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Gramig, Greta |
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STOLTENBERG, DAVID - UNIV. OF WI-MADISON |
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Submitted to: Weed Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/2/2009 Publication Date: 5/1/2009 Citation: Gramig, G.G., Stoltenberg, D.E. 2009. Adaptive Responses of Field-grown Common Lambsquarters (Chenopodium album) to Variable Light Quality and Quantity Environments. Weed Science. 57:271-280. Interpretive Summary: Weed species possess a high degree of morphological plasticity in the changing light environments that characterize highly competitive crop-weed communities. Previously, scientists suggested that a better understanding of this plasticity could help elucidate the underlying basis for phenomena such as critical periods for weed removal and economic thresholds for weed control which are only described empirically. Also, most process-based models of plant competition, which are primarily driven by resource availability and use, tend to neglect plant morphological plasticity as influenced by the light environment. Therefore, field experiments were conducted during 2004 and 2005 to determine whether exposure to reduced red:far-red light ratios (R:FR) during the vegetative growth stage, in the absence of shading among plants, was associated with adaptive changes in morphology, biomass production, and fecundity of common lambsquarters (Chenopodium album L.). At the late-vegetative stage, common lambsquarters plants exposed to reduced R:FR during the vegetative stage exhibited greater specific leaf area, stem elongation, mainstem leaf area, specific stem length, and mainstem biomass compared to plants exposed to ambient R:FR; however, biomass allocation to stems, leaves, and roots did not differ between vegetative stage R:FR treatments. During the reproductive stage, morphology and productivity of plants exposed to partial shade did not differ between vegetative stage R:FR treatments. In contrast, plants exposed to full sunlight during the reproductive stage after exposure to reduced R:FR during the vegetative stage exhibited less total plant biomass, less total leaf area, greater stem elongation, greater specific stem length, and a greater ratio of mainstem to total stem biomass compared to plants exposed to ambient R:FR during the vegetative stage. At physiological maturity, plants exposed to vegetative stage reduced R:FR and reproductive stage partial shade exhibited less total seed mass and fewer seeds compared to plants exposed to vegetative stage ambient R:FR and partial shade during the reproductive stage. In contrast, fecundity of plants exposed to full sunlight during the reproductive stage did not differ between vegetative stage R:FR treatments. Our results illustrate that adaptive plastic responses of common lambsquarters were induced by changes in light quality during the vegetative stage and that these responses were associated with potential fitness costs, such as reduced fecundity and reduced responsiveness to light quality and quantity environments at later stages of growth. Scientists who are seeking to develop more accurate process-based models of crop-weed competition will benefit from this research. Technical Abstract: Field experiments were conducted during 2004 and 2005 to determine whether exposure to reduced red:far-red light ratios (R:FR) during the vegetative growth stage, in the absence of shading among plants, was associated with adaptive changes in morphology, biomass production, and fecundity of common lambsquarters (Chenopodium album L.). Plants were grown in pots and placed in field environments characterized by either reduced (0.3-0.5) or ambient (1-1.2) R:FR, both without shade. At the late-vegetative stage, plants were moved to environments providing either full sun (a non-competitive environment) or partial shade (a competitive crop-weed environment). At the late-vegetative stage, common lambsquarters plants exposed to reduced R:FR during the vegetative stage exhibited greater specific leaf area, stem elongation, mainstem leaf area, specific stem length, and mainstem biomass compared to plants exposed to ambient R:FR; however, biomass allocation to stems, leaves, and roots did not differ between vegetative stage R:FR treatments. During the reproductive stage, morphology and productivity of plants exposed to partial shade did not differ between vegetative stage R:FR treatments. In contrast, plants exposed to full sunlight during the reproductive stage after exposure to reduced R:FR during the vegetative stage exhibited less total plant biomass, less total leaf area, greater stem elongation, greater specific stem length, and a greater ratio of mainstem to total stem biomass compared to plants exposed to ambient R:FR during the vegetative stage. At physiological maturity, plants exposed to vegetative stage reduced R:FR and reproductive stage partial shade exhibited less total seed mass and fewer seeds compared to plants exposed to vegetative stage ambient R:FR and partial shade during the reproductive stage. In contrast, fecundity of plants exposed to full sunlight during the reproductive stage did not differ between vegetative stage R:FR treatments. Our results illustrate that adaptive plastic responses of common lambsquarters were induced by changes in light quality during the vegetative stage and that these responses were associated with potential fitness costs, such as reduced fecundity and reduced responsiveness to light quality and quantity environments at later stages of growth. |
