Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

APS206: Biotechnology & Food Security > Lecture 2: Biology of weeds > Flashcards

Lecture 2: Biology of weeds Flashcards

You may prefer our related Brainscape-certified flashcards:
Gourmet Food flashcards
1
Q

the world population is predictive to reach __ by 2050

A

9 billion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

more than ____ people of not have adequate food

A

800 million

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

___ people live on less than $1 a day

A

1.3 billion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

At least ___% of global food production is lost pre-harvest to weeds, pests & diseases in developed countries

A

30%

- this rises to 40-50% for some crops in the developed world

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

weeds, pests, and diseases are a __ to food security

A

THREAT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Weed control examples:

A
  • cultivation practices
  • biological control
  • chemical control
  • biotech solutions
  • plant breeding strategies
  • integrated control strategies
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

cultivation practises e.g.:

A

good drainage, manuring + liming, choice of crop and varieties, rotation of crops, weeding & good farm hygiene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

biotech solutions to weed control e.g.

A

genetic modification of crops

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

plant breeding strategies to weed control e.g.

A

resistant cultivars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

2 definitions of a weed:

A

“a plant growing in any situation where it is considered to be undesirable”

” A plant growing in the wrong place at the wrong time”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

can weeds be both monocotyledonous and dicotyledonous plants??

A

YES,

can be broad leaved dicotyledonous plants or monocotyledonous e.g. grasses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

is a weed always a weed?

A

no, a plant may be a weed in some circumstances but not in others

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

of the 250,000 plant species in the world only ____ are troublesome weeds

A

only a few hundred

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

plants classified as agricultural weeds possess

A

certain characteristics which contribute to their success

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

biological characteristics commonly possessed by weedy species:

A
  • Competitiveness

- Persisitence

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

competitiveness in weeds:

A

is the ability of weeds to draw resources (light, water, nutrients and CO2) away from crop plants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

persistence in weeds:

A

the ability to survive from year to year on a given area of land despite farmers attempts to control them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

traits contributing to competitiveness and persistence in weeds include:

A
  • rapid seedling establishment
  • high growth rates
  • prolific root systems
  • large leaf area
  • high reproductive output
  • plasticity (the ability to adapt to changes in the environment)
  • type of life cycle to the crop
  • germination characteristic of seeds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

life cycle of weeds: Annuals:

A

complete their life cycle in one season e.g. poppies, nettles, thistles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

life cycle of weeds: biennials:

A

take two years to complete their life cycles e.g. ragwort

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

life cycle of weeds:

A
  • Annual
  • biennials
  • ephermerals
  • perennials
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

life cycle of weeds: Ephermerals:

A

produce several generations of seed per year e.g. hairy bittercress & chickweed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

life cycle of weeds: perennials:

A
  • persists from year to year

- the aerial shoots die back & plants persist vegetatively as stolons, rhizomes, bulbs or tap roots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Perennials: Coltsfoot

A

persists by means of underground rhizomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

perennials: creeping buttercup

A

persists by means of stolons, underground stems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

perennials: wild garlic and wild onion

A

persist by means of a bulb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

understanding there germination characteristics of weed species is important for

A

weed control

28
Q

all agricultural soils have ___ seed banks

A

LARGE

29
Q

things to understand of the large seed banks in agricultural soils

A
  • depth of germination
  • -> most seed have amax depth from which they can germinate depending on seed size and food reserves
  • -> the majority of annual seeds are to be found in the top 5cm of soil
  • periodicity of germination
  • dormancy
30
Q

periodicity of germination:

A
  • most seeds of a given weed species germinate & emerge at a particular time of the year
  • means there is a close association between certain weed sp. and certain crop plants
  • maximum period of germination is known then correct herbicide can be chosen
31
Q

periodicity of germination: Ive leaved speedwell

A

germinates in the autumn and winter and is a problem in winter cereals

32
Q

periodicity of germination: Chickweed

A

emerges in the spring and is a problem in spring and summer crops

33
Q

dormancy is a mechanism that

A

has evolved to ensure survival of the species. Most seed have primary or innate dormancy when they are direct produced

34
Q

primary or innate dormancy may be due to:

A
  • impermeability of the seed coat to water
  • impermeability of the seed coat to gases
  • mechanical resistance to embryo growth
  • immaturity of the embryo
  • the embryo may require a period of drying or cold
35
Q

how do weeds damage crops?

A
  • competition for resources
  • loss in the quality of produce
  • poisoning of livestock
  • harbouring of pests & diseases
  • pollination
36
Q

how do weeds damage crops? competition or resources &

are most weeds parasitic?

A
  • competition for resources (light, water, CO2, nutrients)
  • -most weeds are not parasitic on their hosts & compete, indirectly for resources. Few are parasitic on crop species & Compete for host resources directly
37
Q

the effect of weed density on rice yields:

A
  • as weed density increases, the yield of cultivated rice decreases
  • the extent of the decrease in yield differs depending upon the weed
  • the field decrease occurs as a result of competition for, water & sometimes light
38
Q

competition for water:

A

those plants outcompeted for water are a lot smaller and lack growth

39
Q

where are parasitic weeds important?

A
  • sub Saharan Africa e.g. Strega species

- some Mediterranean agro-ecosystems e.g. Orobanche species

40
Q

how do parasitic weeds lower yield:

A

-Directly compete with the host for host resources (e.g. carbon, nitrogen and inorganic solutes) as they parasitise the host

41
Q

Striga species not only parasitise their host but cause

A

a molecular reprogramming of host development

42
Q

example of 2 root parasites:

A
  • Orobanche cumana (broomrape) (obligate holoparasite)

- Striga hermonthica (witchweed) (obligate hemiparasite)

43
Q

Striga hermonthica & S. asiatica infect:

A

Maize, sorghum, millet & upland rice directly affecting the lives of 100M people in sub Saharan Africa

44
Q

___ ha land infested with Striga seed & yield losses of ___% are common

A
  • 70M ha

- 40-100%

45
Q

Orobanche species infect

A

many legumes & vegetables & Crops such as sunflower, tomato & tobacco

46
Q

where are Orobanche species a problem & how much loss do they cause:

A

problem in Russia, Ukraine, Mediterranean regions, North Africa & the middle east again causing losses form 10-100%

47
Q

control of parasitic weed is ___

A

very difficult

48
Q

Effects of Striga on the host:

A

1) lowers biomass and height
2) Reduction in biomass & grain production due to:
- -utilisation of host nutrients by the parasite (competition)
- -Molecular reprogramming of host growth & development

49
Q

the genus Orobanche includes more than

A

100 species

50
Q

distribution of orobanche:

A

mainly in the mediterranean Basin, but also in Eastern Europe, Former Soviet Union

51
Q

which genus are holoparasitic and what does this mean

A

OROBANCHE, lacks chlorophyll

52
Q

does Orobanche form direct connections with the host phloem & xylem

A

YES

53
Q

how does orobanche lower the yield of host

A

by acting as a very efficient sink for host carbon, nitrogen & inorganic nutrients

54
Q

five species of orobanche for economic important

A 
O. aegyptiaca
O. ramosa 
O. cumana 
O. cernua 
O. Crenata
55
Q

Orobanche parasitised cultivated species:

A

sunflower, cabbage, cucumber, potato, tomato, tobacco, carrot

56
Q

__ ha infected with O. cumana

A

73 million hectares infested with O. cumana

57
Q

Orabanche can lead up to yield losses of up to

A

50%

58
Q

existing management methods have ___ against Orobanche

A

limited success & applicability

59
Q

how do weeds damage crops? loss in the quality of produce

A
  1. Contamination of produce for processing e.g.
    • Wild oats in malting barley
    • Black nightshade berries in peas
  2. Weed seeds are an impurity in crop seed which can lead to failure to reach EEC standards
  3. Harvesting problems
    • The presence of weeds in a crop
    slows down combine harvesters
    • If the weed ripens after the cereal it may raise the moisture content of the grain h increasing drying costs.
60
Q

how do weeds damage crops? Poisoning of livestock

A
  • Many common weeds are poisonous to livestock e.g. ragwort, bracken and hemlock.
  • Most cattle will avoid these species in the field but the real problem come if they get into silage.
  • Horses and cows are more susceptible to ragwort poisoning than other livestock.
  • Young animals are even more susceptible than older animals.
  • Ragwort destroys the liver of the animal by poisoning.
  • Little can be done after clinical symptoms appear.
61
Q

how do weeds damage crops? harbouring of pests & diseases

A

• Weeds may be a problem if they harbour pests and disease of crops.
• Several weed species act as a host for a range of fungal, viral and nematode borne diseases e.g.
– Couch grass/Take-All of wheat – Chickweed/nematodes.

62
Q

how do weeds damage crops? Pollination

A
  • Weeds can compete with trees in orchards for pollination by bees.
  • The flowers of some weeds attract bees more than apple and plum blossom.
  • Weeds in orchards also reduce yield by competing for water and nutrients
63
Q

3 approaches to weed management:

A
  • prevention
  • Eradication
  • control
64
Q

prevention aim:

A

is to keep weed seeds & vegetative materials from being introduced into a field e.g.
–• Make sure that seed that is sown is pure
• Clean implements when moving from one field to another
• Mow weeds in field borders to prevent seed se

65
Q

Eradication: because weeds are persistent once they become established it is _____ to eradicate them

A

is almost impossible and impractical

66
Q

Eradication is ___ attempted

A

RARELY

and is only considered when a noxious weed has been inadvertently introduced from one area to another.

67
Q

a successful eradication programme requires:

A

a long term connected effort consisting of several preventative & Control measures e.g. the attempt to eliminate Striga from the USA

APS206: Biotechnology & Food Security (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions