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Corn Leaf Architecture Response to Plant Density

 

Corn Leaf Architecture Response to Plant Density

Background & Objectives

  • Previous research has shown that corn plants can alter their leaf angle and orientation in response to their environment.
  • At greater densities, plant leaf angle tends to be more upright and leaves may preferentially orient toward the interrow in order to optimize capture of sunlight.
  • Plasticity of both leaf angle and leaf orientation in response to plant density has been shown to differ among hybrids.
  • A research study was conducted in 2014 to evaluate leaf angle and orientation response to plant density with 2 Pioneer® brand corn products.

Study Description

Location: Johnston, Iowa
Replicates: 4
Plot Layout: Small plots (10 x 17.4 ft), RCBD                 
Row Width: 30 inches
Planting Date: May 5, 2014
Factors:
  • Pioneer® Hybrid/Brand1:   
  • P0636AM™ (AM, LL, RR2)
    P1162AMX™ (AMX, LL, RR2)
  • Population:  30,000, 40,000, and 50,000 plants/acre
  •  

    Leaf Measurements

    • Leaf angle and orientation measurements were taken on the15th leaf of 10 plants in each plot.
    • Measurements were taken on July 17, 2014.
    • Leaf angle
      • Angle of the leaf relative to the stalk
      • Measured at the base of the leaf using a clinometer smartphone app (Figure 1).
    • Leaf orientation
      • Direction of the leaf relative to the row (0º = parallel to the row, 90º = perpendicular to the row).
      • Measured using a compass smartphone app.
      • Orientation of each leaf was classified as parallel (0º to 22.5º), intermediate (22.5º to 67.5º), or perpendicular (67.5º to 90º) to the row.
      • Expected distribution among leaf orientation categories, assuming a random azimuthal distribution, would be 25% parallel, 50% intermediate, and 25% perpendicular.

    Figure 1. Leaf measurements were taken using smartphone apps
    (Johnston, Iowa; July 17, 2014).

    Photo: Leaf measurement app on smartphone

     

    Results

    • Plant density did not have a significant effect on leaf orientation for either corn product.
    • Leaf orientation differed between corn products.
      • Pioneer® P1162AMX™ brand corn had a significantly greater proportion of leaves oriented perpendicular to the row than Pioneer® P0636AM™ brand corn (Figure 2).
      • The proportion of leaves of P0636AM™ was close to what would be expected based on random azimuthal distribution.
      • The greater proportion of perpendicular leaves with P1162AMX™ suggests a greater genetic ability to alter leaf orientation in response to environmental conditions.

    Figure 2. Proportion of leaves oriented parallel and perpendicular to the
    row of 2 Pioneer brand corn products.

    Chart: Leaf orientation for corn products

     
    • Leaf angle was significantly influenced by both plant density and corn product.
      • The average angle of leaf 15 at 50,000 plants/acre was 19.9º, which was significantly more upright than the average angle at 30,000 plants/acre, 21.2º (Figure 3).
      • The average angle of leaf 15 was significantly more upright for P0636AM™ than P1162AMX™ (Figure 4).
    • A much greater range in leaf angle was observed in a survey of several corn products in non-replicated demonstration plots at the same location (Figure 5).

    Figure 3. Average angle of the 15th leaf (degrees from vertical) as affected
    by plant density.

    Chart: Average angle of the 15th leaf by plant density.

     

    Figure 4. Average angle of the 15th leaf (degrees from vertical) by corn
    product.

    Chart: Average angle of the 15th leaf by corn product.

     

    Figure 5. Average angle of the 15th leaf (degrees from vertical) of several
    Pioneer® brand corn products in Johnston, Iowa, demonstration plots in 2014.

    Chart: Average angle of the 15th leaf of several Pioneer® brand corn products

     

    Conclusions

    • The results of this study demonstrate the ability of corn plants to adjust their leaves in response to their environment; however, the capacity to do so differs among corn products.
    • Future efforts to optimize the crop canopy for maximum light utilization and yield need to take this effect into account.
    • Results suggest that differences in leaf architecture associated with response to plant density are likely relatively small compared to inherent genetic differences.



    1
    All Pioneer products are hybrids unless designated with AM1, AM, AMRW, AMX and AMXT, in which case they are brands. 2014 data are based on average of all comparisons made in one location through August 1, 2014. Multi-year and multi-location are a better predictor of future performance. Do not use these or any other data from a limited number of trials as a significant factor in product selection. Product responses are variable and subject to a variety of environmental, disease, and pest pressures. Individual results may vary. PIONEER® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents.

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