Shade Avoidance Influences Stress Tolerance in Maize

[ "Postdoctoral research associate, postdoctoral research associate, graduate student, Professor, and Professor, Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road E., Guelph, ON N1G 2W1, Canada. Current address of first author: Agriculture and Agri-food Canada, Greenhouse and Crops Processing Centre, 2585 County Rd. 20, Harrow, ON N0R 1G0, Canada. Corresponding author's E-mail: "]
Weed Science (Impact Factor: 1.87). 07/2011; 59(July-September 2011):326-334. DOI: 10.1614/WS-D-10-00159.1


Previous studies have suggested that the reduction in the root/shoot ratio that accompanies the shade avoidance response may reduce the tolerance of individuals to subsequent nutrient or moisture limitations. In this work, we examined the impact of the shade avoidance response on maize seedling growth and development and the response of these plants to a subsequent abiotic stress. Seedlings were grown in a field fertigation system under two light quality environments, ambient and a low red to far-red ratio, which were designed to simulate weed-free and weedy conditions, respectively. This system also enabled the controlled restriction of water and nutrients, which reduced the relative growth rate of the crop and created a secondary stress. Results of this study indicate that, while the shade avoidance response did reduce the root/shoot ratio in maize, this effect did not reduce plant tolerance to subsequent abiotic stress. Rather, the apparent additivity or synergism of shade avoidance and the secondary stressor on yield loss depended on whether the net effect of these two stressors was sufficiently large to shift the population toward the point where reproductive allometry was broken. Nomenclature: Maize, Zea mays L.

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    • "The pH of the diluted solution was adjusted to 6.5–6.7 by the addition of HCl. Two fertigation tubes calibrated to deliver a minimum of 10 ml of nutrient solution per minute were inserted into each pail (Page et al., 2011). For the positive nitrogen treatment (+N), 1.1 g of urea was dissolved into 1 L H 2 0 (37 mM total N, to compensate for leaching) and was provided to the plants at weekly intervals (13 times total) over the course of the experiment, with control "
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    ABSTRACT: The small grain cereal, finger millet (FM, Eleusine coracana L. Gaertn), is valued by subsistence farmers in India and East Africa as a low-input crop. It is reported by farmers to require no added nitrogen (N), or only residual N, to produce grain. Exact mechanisms underlying the acclimation responses of FM to low N are largely unknown, both above and below ground. In particular, the responses of FM roots and root hairs to N or any other nutrient have not previously been reported. Given its low N requirement, FM also provides a rare opportunity to study long-term responses to N starvation in a cereal species. The objective of this study was to survey the shoot and root morphometric responses of FM, including root hairs, to low N stress. Plants were grown in pails in a semi-hydroponic system on clay containing extremely low background N, supplemented with N or no N. To our surprise, plants grown without deliberately added N grew to maturity, looked relatively normal and produced healthy seed heads. Plants responded to the low N treatment by decreasing shoot, root, and seed head biomass. These declines under low N were associated with decreased shoot tiller number, crown root number, total crown root length and total lateral root length, but with no consistent changes in root hair traits. Changes in tiller and crown root number appeared to coordinate the above and below ground acclimation responses to N. We discuss the remarkable ability of FM to grow to maturity without deliberately added N. The results suggest that FM should be further explored to understand this trait. Our observations are consistent with indigenous knowledge from subsistence farmers in Africa and Asia, where it is reported that this crop can survive extreme environments.
    Frontiers in Plant Science 08/2015; 6:652. DOI:10.3389/fpls.2015.00652 · 3.95 Impact Factor
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    • "It has been proposed that the reduced root investments upon low R:FR exposure are one reason why weeds early in the growing season can have lasting negative effects on crop yield at the end of the growth period. The presence of weeds leads to FR enrichment through reflection FR, thereby promoting shoot over root growth in the crops (Page et al., 2011), and these impoverished root systems may be less able to acquire belowground resources (Rajcan et al., 2004). Likewise, natural populations of Impatiens capensis become more sensitive to drought when expressing shade avoidance responses as compared with less shadeavoiding populations, presumably through reduced root investments in shade-avoiding plants (Huber et al., 2004). "
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    ABSTRACT: Environmental stresses, such as shading of the shoot, and drought and salinity of the soil, threaten plant yield and survival. Plants can alleviate the impact of these stresses through various modes of phenotypic plasticity. Here we review the current state of knowledge on the mechanisms that control plant developmental responses to shade, salt and drought stress. Plant hormones and cellular signaling pathways that control shoot branching and elongation responses to shade and root architecture modulation in response to drought and salinity are discussed. Since belowground stresses also result in changes aboveground and vice-versa, we subsequently outline how a wider palette of plant phenotypic traits is affected by the individual stresses. We argue for a research agenda that integrates multiple plant organs, responses and stresses. This will generate the scientific understanding needed for future crop improvement programs aiming at crops that can maintain yields under variable and sub-optimal conditions.
    Plant physiology 06/2014; 166(1). DOI:10.1104/pp.114.239160 · 6.84 Impact Factor
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    • "Th e eff ect of weed competition or drought stress, in combination with maize dwarf mosaic infection, was additive during the vegetative stage of sweet corn growth (Olson et al., 1990; Williams and Pataky, 2012). Weed competition in combination with water and nutrient stress resulted in an additive, not synergistic, decline in fi eld corn biomass at maturity (Page et al., 2011). "
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    ABSTRACT: Competition among crop plants (i.e., intraspecific) and between crop and weed plants (i.e., interspecific) likely co-occurs in many sweet corn (Zea mays L.) fields; however, a fundamental understanding of the extent to which the crop is affected by the combination of these stresses is unknown. The objective of this work was to identify the extent to which seeding level influences the crop's tolerance to weed competition in terms of crop development, yield, and profitability. In field research in Illinois and Washington, two hybrids with different levels of tolerance to weed competition were planted each of 2 yr at five seeding levels each year and grown in the presence and absence of wild-proso millet (Panicum miliaceum L.). The crop's ability to tolerate intraspecific and interspecific competition was additive, as evidenced by no significant interaction between seeding level and weed competition for thermal time to mid-silk, marketable ear number, marketable ear mass, and gross profit margin to the rocessor. Losses in gross profit margin due to weed competition alone ranged from $ 2,400 to $ 8,100 ha(-1). Hybrids used in this work showed differential tolerance to interspecific competition, but of the seeding levels tested, neither hybrid was consistently more tolerant to intraspecific competition. Across years and hybrids, the seeding level that consistently did not delay silking but maximized marketable ear number, marketable ear mass, and gross profit margin to the processor was 70,000 and 88,200 ha(-1) in Illinois and Washington, respectively. Improving weed management efficacy and genetic tolerance to competition off er two approaches to improving sweet corn productivity.
    Agronomy Journal 12/2013; 105(2):503-508. DOI:10.2134/agronj2012.0381 · 1.44 Impact Factor
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