Weed Test 1 Flashcards
weed
any plant out of place or growing where it is not wanted WSSA definition: any plant that is objectionable or interferes with the welfare of man or natural systems
ligule
tissue clasping the stem inside the leaf at the junction of the blade with the sheath. (present when you pull back the leaf)
auricle
appendages projecting from either side of the collar (look like fingers)
collar
a thickened, often apparently vein-less, shelf-like band marking the junction of the blade and sheath (unfold and keeps coming down)
flower
stem or branch bearing highly modified leaves concerned with sexual reproduction
fruit
a mature ovary plus attached floral or vegetative structures that become enlarged and ripen with it
seed
a mature ripened ovule
safe site
safe place where seed is allowed to germinate without competition or predators and has the right resources needed
carrying capacity
max population size of a species that the environment can sustain
dormancy
state of suspended development even though conditions are environmentally conductive for germination
quiescence
inhibition of germination when complete requirements are not met
persistence
the ability of a community to remain relatively unchanged over time
resistance
the ability of a community to remain unchanged during a period of stress
resilience
the ability of a community to return to its original state following stress or disturbance
elasticity
the speed at which the system returns to its former state following a disturbance
losses caused by weeds
reduction of crop yields
increased cost of operations
reduction in quality or quantity
increased processing costs
depreciated land values
reduced crop choice
allergies and poisoning
aesthetics
ideal characteristics of weeds
ability to germinate in many environments
discontinuous germination and seed longevity
rapid growth
continuous seed production
self pollination
cross pollination
high seed output in adverse conditions
adaptions for dispersal
ability to compete interspecifically by special means
most important general characteristics of problem weeds
number of individuals produced
range of habitats
ability to continue
monocot
one cotyledon
parallel leaf veins
hollow stems with vascular bundles scattered throughout
underground: bulbs, corms, rhizomes
flower parts in 3’s
ex: grasses
dicot
2 cotyledon
net veination of leaves
stems with vascular bundles in a ring around pith or woody stems surrounded by bark
no scaly bulbs
flower parts in multiples of 2 or 5
ex: broadleaf plants
weed crop ecosystem components
weeds
crops
humans
natural environment
weed crop ecosystem concepts
understanding aids in developing weed management programs
traditional concepts focused only on weed and crop
now geared more toward specific weeds in a given crop in a single year
species have changed in response to weed control and other practices
weed species shifts
changed in response to weed control and other production practices
environmental factors
climate
physiographic
biotic
climate factors
light
temp
water
wind
atmosphere
physiographic factors
soil factors: pH, fertility, texture, structure, organic matter, CO2, O2, water drainage
topographic: altitude, slope, exposure to the sun
biotic factors
plants (competion, toxins/stimulants, diseases, parasites, soil flora)
animals (insects, grazers, soil fauna, man)
population
group of individuals that occupy an area within an environment which permits interbreeding among the group
population characteristics
density
age distribution
growth form
adaptiveness
persistance
reproductive fitness
birth and death rates
dispersion
what gives population structure
variation of individuals within population such as age, size, stage of development, and other physical and genetic features
niche
a species place and role in a community
niche separation
refers to the process by which natural selection drives competing species into different patterns of resource use or different niches
plant succession
an orderly change in species resulting from modification of the physical environment by the plant community
resource allocation
ability to accommodate and maximize growth over a wide range of light and temperature interactions
weeds are dispersed over
time (dormancy)
space (physical movement)
reasons for dispersal of weeds
avoid competition between parents and siblings
increase colonization opportunities
reduce predation chances
special adaption of weed seeds for dispersal
saccate fruits (floats) winged fruits and seeds (expanded wings or margins) comate seeds (long hairs or bristles) parachute fruits (spreading tufts or bristles) plumed fruits (long branched plume) clinging fruits (prickles, barbs, burs)
dispersal of weed seed by man
seeds on clothes or shoes ballast/trash from boats hay and feedstuff digestive tract spreading manure equipment packing materials mixed in crop seed
federal seed act
1939 provides for regulation of transport and sale of seeds in both foreign and interstate commerce seed label include: kind, variety, type of seed exceeding 5% origin of lot % by weight of seed kinds of noxious weed seeds and occurrence % other seeds and inert matter %germination and % hard seed with test date name and address of shipper or receiver
types of dormancy
innate (genetic) induced (environmental) enforced (environmental)
innate dormancy
impermeable or resistant seed coat
chemical inhibitor (delays germination)
rudimentary embryo (not fully developed)
induced dormancy
conditions cause seed to go into secondary dormancy, don’t germinate at first with favorable conditions, but do eventually
causes: excessive light, lack of moisture, high CO2, low O2, high temp
enforced dormancy
conditions cause seed not to germinate but when favorable conditions arise, germination occurs
seed bank
seeds of different ages and dormancy levels that make up the seeds which could germinate in a given land area
transient seed bank
seeds persist for a short period of time (1 yr or less) and remain near soil surface
persistent seed bank
seeds remain dormant and become incorporated into the soil, persisting for long periods and stabilizing area
