AGRON 330 - Exam 1

Traits of a Weedy Plant

Environmental plasticity

Weed Seed dormancy

rapid growth during V - R stages

Continuous seed production

self-compatible

when cross pollinated, doe by visitors or wind

high seed ouput

produces seeds in wide range of climates

seeds have adaptations for dispersial

Perennial, vigorous vegetative repro

Brittle and regeneration fragments

compete inter-specifically

Environmental plasticity

germination requirements fullfilled in many environments

grow in wide range of climate and soil conditions

exist everywhere land is disturbed

Weed Seed dormancy

dispersal in time

germination is discontinuous

long-lived seeds

Self-Compatible

not completely autogamous (self-fert) or apomictic (no fert)

Regeneration from fragments

Dual modes of reproduction

rhizomes, stolons, tubers, bulbs, etc

Harmful aspects of weeds on crops

yield loss

quality loss

limit management choices

harbor other pests

interfere harvesting

increasing processing of harvest crops and transportation

Yield Loss

weeds capture space, nutrients, water, and sunlight from beneficial plants

Quality of farm products

difficult to separate

jointed goat grass can cross-pollinate with wheat

limited management

limit crop rotations

can not adapt no-till

Harmful aspect of weeds on humans

human discomfort

poisonuous

spines, thorns, and stickers

aesthetic value on property

Harmful aspects of weeds on livestock

grazing of poisonous plants

reduced quality of grazing land

Ethnobotony

study of uses of plants by people

relationship between people and vegetation

dependence on the weeds

Classification by Habitat

terrestrial

aquatic

aeril

terrestrial

live on ground, crops, rangeland

Aquatic

live in, on, or near water

Aeril

Plants, not rooted in soil

epiphytes

Classification by Taxonomy

Algae

Mosses and Liverworts

Ferns and Horsetails

Gymnosperms

Angiosperms

Algae

Freshwater: phytoplanton, filamentous, charra

Mosses and Liverworts

turf and nursery condition

occur in low pH, low sunlight, excess moisture, compaction

Ferns and Horsetails

scouring rush, field horsetail in crops

braken ferns in pastures

non-flowering

Gymnosperms

mostly trees in Range and forest ecosystems

Eastern red cedar - native to KS, little berries, cut below lowest green

Angiosperms

Flowering plants, produce seeds

most are monocots, fewer are dictos

Classification by Physiology

C3, C4, CAM

C3

soybean, lambsquarters

C4

corn, pigweed, shattercane

CAM

cactus plants

Summer Annual

germinate in spring and summer, mature before winter

Examples of summer annual weeds

foxtails and pigweeds

Winter annual

germinate late spring, early fall mature

Examples of winter annual weeds

henbit

mustard

Biennial

2 growing seasons to complete cycle

seeds germinate and grow vegetatively as a rosette

only be seed

Examples of biennial weeds

musk thistle

common mullen

garlic mustard

Perennial

a plant that lives indefinitely, multiple years

Simple Perennial

grow vegetatively, from crown of tissue or below top soil on taproot

Examples of simple perennial

common dandelion

curly dock

common pokeweed

Creeping perennial

seed, vegetative, reproduce vegetative structures

Examples of creeping perennial

common milkweed

field bindweed

johnsongrass

Seed characteristics

encapulate embryo

own energy seed

special structures

dormancy

Seed

mature, fertilized ovule, orplant embryo, that has stored energy reserves and protective coats

Vegetative Reproduction

any plant part that can produce new plant

Stem tissue

bulbs, rhizomes, stolons, tubers

Root Tissue

adventitious buds and root stock

Asexual

Apomixis

vegetative

Apomixis

no pollination (dandelion)

vegetative

no embryo (all rhizomes, stolons, etc)

examples of self pollination

shepardspurse

henbit

Cross pollination

another of on e flower to another

Monoecious

male and female are on same plant

common ragweed and corn

Dioecious

male and female are on separate flowers

waterhemp, Palmer, eastern red cedar

Dispersal

entry of weed seeds into seedbank

Why do weed seeds get stored in the seedbank?

reduce competition with siblings

genetic diversity

explore new environments

decrease predation

Seeds are dispersed through

wind

water

animals

predation

machinery

human-aided

Wind dispersal

weight, shape, structures, height, and wind speed

Water dispersal

corky seed, air-filled bladders, flat, light-weight

Animals

contaminated feed and incompuate digestion of seed

Chickens are better at digesting the seeds

Caching

collection and storing of seeds (earthworm)

Projection (explosive)

1 - 20ft

wild cucumber and touch-me-not

Machinery

tillage, harvest, field-to-field movement

Human-aided

animal feed, sow contaminated crop seed,

non-screened irrigation water

ornamental plants

manure

Pre-dispersal predation

insects - birds eat seed while still on plant

Post-dispersal predation

exclosures to keep certain predators from entering

determine portion of seeds that each predator eats

20-30% seed loss just due to predators and insects

20 - 30% seed loss due to

predators and insects

Seedbank

reservoir of viable seeds and or vegetative propagueles on soil

Moldboard plow

disturbs the soil and flips the seedbank

No-till leaves the weed seeds at

the top of the soil

Vertical distribution

no-till vs moldboard, more seeds on top with no-till

Horizontal distrubtion

study between seed bank and seedlings

moldboard plow had higher seedbank and seedling than no-till

Fates of Weed seed in Soil

Death

Germination

Dormancy

Death

microbial activity (rots in soil)

Predation (insects, rodents, and birds)

Fatal Germination (too deep to reach the surface)

Germination

a seed will begin to grow with proper environment

Dormancy

seed in a state of suspended animation, living not growing

What is the largest influence on long-term persistance of weeds?

dormancy

Factors Affecting longevity and survival of propagules

depth of burial

temperature

food reserves

Propagules have _____ survival rates compared to seeds

low

Environmental-Based conditions that cause dormancy

light

oxygen

temperature

moisture

light

most important cause of dormancy

50% of annual weeds need light

Phytocrome

Promoter

red light (lots of sunlight)

Inhibitor

far-red light (under canapy)

Oxygen

higher o2 results in more germination

more o2 at surface of the soil

compaction reduces o2

Temperature

optimum range varies by species

prevents germination below or above the range

Moisture

soil wetting and drying cycle

Seed-Based Dormancy Factors

Immature embryo

impermeable seed coat

chemical inhibitors

after-ripping requirement

Immature embryo

seed shed from plant with immature embryo

smartweed species

Impermeable seed coat

hard seed coats don't let oxygen and water

break seed coat through scarification, microbes, action of acids

lets the radicle penetrate the seed coat

Chemical inhibitors

remove internal chemicals through leaching of water

After-ripping requirement

seeds embryo is fully developed

poorly understood physiological change needed before germination occur

Classes of Dormancy

innate

enforced

induced

Innate Dormancy

condition of seed at time of production and dispersal

Causes of Innate Dormancy

inherent property

chemical properties

hard seed coat

Enforced Dormancy

improper environmental conditions at the time seed normally germinates

Causes of Enforced Dormancy

missing key conditions: water, temp, 02, etc

Induced Dormancy

some env. induced seed not to germinate

conditions changed, but no germination

Causes of induced dormancy

high temps, drought, etc

1-12% of viable seeds will

germinate in a year

Main factor driving emergence patterns

Soil temperature: crop residue, soil type, slope, soil moisture

Weed Ecology

Interaction of weeds and their environment

Competition

negative on plant and weed

Parasitism

negative on plant, positive on weed

Allelopathy

release of chemicals from living or decaying plant tissues into the environment that interferes with growth of living plant

Examples of Parasitism

field dodder

mistletoe

witchweed

broomrape