Herbicide Movement In Plants
1) Symplastic movement
• It is source to sink translocation.
• The herbicides move through phloem with sugars or photosynthates produced during photosynthesis.
• Sinks are the sites where sugars translocated from the source are used for growth process or stored.
• Source is nothing but fully expanded any growing leaves
• Sink is nothing but buds, growing shoots, roots, flowers, fruits and seeds.
• Sugars while moving from source to sink through symplast carry along some post emergent herbicides.
• In all foliage applied and post-emergent herbicides the herbicide movement is called symplastic movement.
• It requires metabolic energy and the movement is basipetal (apex to base).
• Symplastic movement is always through phloem. e.g., Glyphosate, 2, 4-D 2) Apoplastic movement
• The herbicides are primarily absorbed by the roots and move predominantly through xylem and intercellular spaces in plants.
• They move along with water (passive movement) or mineral nutrient ions (active movement).
• Therefore the herbicide molecules movement may or maynot require metabolic energy.
• In soil applied or pre-emergent herbicides the usual basis of herbicide movement is apoplastic movement.
Factors Affecting The Efficiency Of Herbicides
1) Soil Applied Herbicides
a) Soil moisture: It is of prime importance to soil applied herbicides. Optimum soil moisture is important. Too dry or too low or very high moisture conditions are undesirable.
b) Soil texture: Smaller the soil particles greater the surface area and more https://www.cimamedicalcentre.com/services/viagra-generic.html absorption of herbicide is likely to occur. Clay will absorb more herbicide than sand.
c) Organic matter: Higher the organic matter content greater is the adsorption of herbicide and less herbicide is available for plants uptake and it will reduce herbicide activity. So dose of herbicide should be increased to accomplish desired level of weed control.
d) Runoff: Herbicide is subjected to lateral movement with runoff water if it rains immediately or within few days after application of herbicide.
e) Temperature: At higher temperature conditions greater uptake and translocation of herbicide is expected to occur because of higher translocation. Metabolism of herbicide may also take place at higher rates. Ex: Atrazine.Atrazine loses selectivity to maize when temperatures are very low.
f) Use of recommended herbicide
g) Dosage of herbicide
h) Time of application
2) Foliage Applied Herbicides
a) Plant morphology: Canopy surface, leaf orientation or angle, location of growing points, hairiness, and presence of waxy layer on stem.
b) Relative humidity: If the relative humidity is high the spray solution may evaporate more slowly and there will be more opportunity time for the droplets to penetrate the leaves.
c) Spray drift
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