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Herbicide Absorption: Foliar - Lecture Slides | PLNT 4070, Study notes of Agricultural engineering

Material Type: Notes; Professor: Kniss; Class: Laboratory; Subject: Plant Sciences; University: University of Wyoming; Term: Fall 2008;

Typology: Study notes

Pre 2010

Uploaded on 08/19/2009

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Herbicide Absorption: Foliar
Weed Science & Technology
PLNT 4070/5070
November 10, 2008
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Herbicide Absorption: Foliar

Weed Science & Technology

PLNT 4070/

November 10, 2008

Plant Foliar Surfaces

Cuticular membrane is a major barrier to

penetration of foliar applied pesticides

  • Cuticle plays a role in spray contact and retention as well as penetration

Much more difficult for a pesticide to enter

the plant through the foliage than the root

  • All above ground plant parts are covered by a cuticle

Cuticle Composition & Structure

Cuticle thickness and composition

influenced by:

  • age of plant
  • environment (temperature, humidity, moisture, light) - Field bindweed: Non-irrigated Irrigated g/100 leaves 5.4 11 mg wax/g leaf 1.5 0.

Cuticle Composition & Structure

Epicuticular waxes

  • Mixture of long chain alkanes, alcohols, ketones, esters, and fatty acids
  • (^) Lipophilic (non-polar)
  • Predominant chain length 21 to 37 C units

Embedded waxes

  • Contain lesser quantities of hydrocarbons
  • Greater proportion of polar constituents

Cuticle Composition & Structure

Pectin

  • Pectin strands located either at cutin cell wall interface or are interspersed in the cutin layer
  • (^) They are the most hydrophilic component of the cuticle

Absorption

Movement of material into plant from an

external surface

Influenced by:

  • Contact & retention
  • Penetration

Contact & Retention

Factors that influence herbicide contact and

retention on the leaf surface:

  • Special structures
    • trichomes
    • stomata
    • veins
    • bladder hairs

Contact & Retention

Factors that influence herbicide contact and retention on the leaf surface:

  • Leaf morphology
    • angle
    • shape
    • width

Contact & Retention

Ramsdale & Messersmith (2001) demonstrated CHEAL retained only 25% as much spray solution as AMARE Redroot Pigweed Common Lambsquarters

Contact & Retention

Factors that influence herbicide contact and

retention on the leaf surface:

  • Environment
    • temperature
    • humidity
    • light
    • wind
  • Cuticle
    • thickness
    • type of wax
    • wax structure

Penetration

Involves:

  • Penetration through the cuticle
  • Penetration through cell walls
  • Penetration through the plasmalema
  • Release into cytoplasm

Cuticular Membrane Penetration

Two routes of entry:

  • Lipid soluble
  • Water soluble

Affected by:

  • Formulation
  • pH
  • Particle size
  • Cuticle thickness
  • Environment

Plasmalema Penetration

Plasmalema composed of lipids or

lipoproteins

  • Minor barrier to penetration
  • Two routes:
    • Active
      • Energy required
    • Passive
      • Difusion
      • Gradient differences