UNIT VII Flashcards
It is a plant growing out of place
Weed
Weeds can be classified into 4 categories, what are they?
- Growth Habit
- Lifespan
- Body Texture
- Habitat
Name the three types of weeds based on growth habit.
- Vines
- Shrubs
- Trees
Name the three types of weeds based on lifespan.
- Annuals
- Biennials
- Perennials
Name the two types of weeds based on body texture.
- Woody
- Herbaceous
Name the three types of weeds based on habitat.
- Terrestrial
- Epiphytic
- Aquatic
Classification of weeds based on gross morphology.
- Grasses
- Sedges
- Broadleaf
What families do grasses belong?
- Graminaceae
- Poaceae
To which family do sedges belong?
Cyperaceae
To what families do broadleaves belong?
- Monocotyledonae
- Dicotyledonae
They are weeds, which are highly competitive and persistent; they reduce crop yields even at low densities and are difficult to control.
Noxious Weeds
These type of weeds have fully expanded leaves, the leaves have netted venation.
Broadleaves
These weeds bear a close resemblance to the grasses and can be distinguished by a thin triangular stem. They have an absence of nodes and internodes, ligules, the fusion of leaf forming a tube around the stem.
Perennial versions of these weeds have underground tubers or rhizomes.
Sedges
These weeds range from small, twisted, erect or creeping annuals or perennials. Stems are called culms and with well-defined nodes and internodes, while the leaves are alternately in two rows from the nodes.
Grasses
What are the 3 types of aquatic weeds?
- Emergent
- Floating
- Submerged
What type of aquatic weed has the upper portion is above water but roots are anchored to the ground.
Emergent
What type of aquatic weed has all parts are under water?
Submerged
What type of aquatic weed has the upper portion is above water but roots are not anchored to the ground
Floating
It is a mechanism through which a species survives unfavorable conditions including control operations. It refers to the rest period of the seed.
Seed Dormancy
What are the mechanisms of dormancy?
- Physical/Structural Mechanism
- Physiological Mechanism
Which mechanism of weed seed dormancy refers to the impermeability of the tissue surrounding the seed or embryo to water and/or oxygen.
Physical/Structural Mechanism
This type of mechanism of weed seed dormancy can be caused by an immature embryo or by the the presence of inhibitors?
Physiological Mechanism
It is the lapse of time required for the seed to overcome its physiological barrier for germination.
After ripening
What mechanism in the hilum can also control limitation of water
imbibitions in hard seeds.
A hygroscopically activated valve
This dormancy in weed seeds is acquired as the seed or organ develops or matures.
Primary, natural, or innate seed dormancy
This dormancy in weed seeds is due to unfavorable conditions.
Secondary or Enforced Dormancy
It is a method of breaking seed dormancy wherein the seeds are exposed to a lower temperature.
Stratification
Give the 3 methods of Weed Control
- Mechanical Weed Control
- Chemical Weed Control
- Biological Weed Control
Weeds are controlled using a rotating hoe (rotary or conical weeder) to cultivate, uproot and bury emerging young weeds between rows of rice plants.
Mechanical weeding
Why do we need to control weeds?
- prevent yield loss
- maintain quality & market price of produce
- prevent build-up of weed seeds in soil
- prevent weeds that attract rodents, insects, and diseases
- prevent clogging of irrigation channels
- reduce time and cost in land preparation and weeding operations
This type of weed control uses chemicals called herbicides to kill certain plants or inhibit their growth.
Chemical Weed Control
It is the resumption of growth.
Germination
How many stages of germination are present? Please enumerate.
- Imbibitions
- Period of rapid metabolic activity
- Emergence of root
- Emergence of shoot
- Period of independent growth
This phase is purely a physical process. It involves the absorption of water by starch and can take place in living and dead seeds.
Imbibitions 1
This phase is physiological and water is absorbed by the embryo. It marks the initiation and progress of starch hydrolysis
Imbibitions 2
During this period, cell division and cell elongation proceed at a fast rate supported by a rapid synthesis of materials.
Period of Rapid metabolic activity
What are the factors affecting the Growth of Weeds?
- Light
- O2
- Temperature
- Moisture
- Carbon Dioxide
What are the major factors influencing Flowering and Seed Production?
- Photoperiod/Daylength
- Vegetative Growth
- Temperature
- Growth regulators
This determines the spread of the weed. Adaptive structures and
proper habitat as well as activities of man contribute to it.
Dispersal of Weed Propagule
It is the term used to refer to the structure, usually single-seeded together with accessory parts, that is dispersed or separated from the mother plant and whose function is to perpetuate its kind in other areas.
Dispersal Unit
What are the agents of weed dispersal?
- Man
- Animals
- Wind
- Water
In ancient times, the Chinese discovered that increasing ant populations in a citrus groves helped decrease destructive populations of what insect pests?
- Large Boring beetles
- Caterpillars
These insects feed directly on the weed roots causing injury which allows bacteria and fungi to penetrate.
Beneficial Nematodes and Insects
What is the term used for insects, pathogen etc. and other animals that are used to control weeds?
Bioagent
This weed control method can reduce weeds but not totally eradicate the entire weed population.
Biological control
What are the 2 methods used in Biological Control of Weeds?
- Augmentation of Natural Enemies
- Biological Herbicides
This method in Biological Weed Control includes the periodic release and/or distribution of natural enemies.
Augmentation of Natural Enemies
A new approach to biocontrol of weeds has recently been pioneered in
Arkansas with the application of a spore suspension of an endemic fungus.
Biological Herbicides
