Biology Video Key Points

The key points of the Biology video are compiled in this document

Biology Video Key Points

Grasses                     1 leaf narrow upright leaf at germination, parallel veins, fibrous root system, growing points near or below surface

Broadleaves            2 leaves at germination, broad leaf with netted veins, coarse root system, growing points on stem and roots

Woody –         Trees and shrubs – deciduous or conifers

Stages of Development

Seedling – Small succulent – Most easily controlled

Vegetative – Rapid growth

Reproductive – Flowers and seeds

Maturity – Post reproductive

Life Cycles

Annual – all stages less than 1 year

Winter annual – germinates fall matures in spring

Fall is best time for control

Summer annual germinates spring and dies in fall

Spring is best time to control

Biennial – 2 years

1st year – Vegetative stage – rosette – Best time for control

2nd year – Matures and seeds

Perennial – multiple years

Best to control as seedling

Persistent roots, effective control must kill roots

Simple – spreads by broken bits

Creeping – stolons, roots at joints, horizontal stem at surface

rhizomes – underground horizontal stems

Bulbous – tubers, bulbs, nutlets


Xylem – moves herbicide, water, and nutrients up

Phloem – moves herbicide and plant food from foliage to roots

Grasses have vascular bundles which contain xylem and phloem

Trees and shrubs

Bark – phloem

Woody – xylem

Cambium – area between xylem and phloem, responsible for increases in tree diameter

Herbicide works best when plant is actively growing

Environmental Factors – Water, Soil, Temperature

1. WATER – Transport medium to move nutrients and herbicides from root to leaf

Sugars and foliar applied herbicides move from leaf to roots.

Water is key in photosynthesis

Rain carries herbicide to root zone

2.  SOIL

Soil texture depends on percentages of sand, silt, clay

Coarse or light soil is high in sand

Fine or heavy soils are high in clay

Dark soils are high in organic matter (OM), decaying plants and animals.

As clay   increases  – Adsorption  increases  – Leaching decreases  
Herbicide use  or application rate increases  

As OM increases – Adsorption increases – Leaching decreases
Herbicide use or application rate increases

As sand increases – Adsorption decreases – Leaching increases
Herbicide use or application rate increases

3. Temperature
As temperature increases
Plant activity increases
Speed of herbicide effect increases

As soil temperature increases – persistence of herbicide decreases




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