Lecture 8 - Weed-Crop Interactions

Question 1

competition

Answer 1

process that occurs when combined resource demand of plants within a given area exceeds supply

Question 2

what are plants competing for

Answer 2

light, water, nutrients, oxygen, carbon dioxide

Question 3

interference

Answer 3

combination of all negative plant interactions including competition, allelopathy, and parasitism

Question 4

2 types of plant interactions

Answer 4

intraspecific interactions (within species)
interspecific interactions (between species)

Question 5

law of constant final yield

Answer 5

yield independent of plant density at high densities (# of seeds produced and individuals in an environment can be maxed out even with unlimited resources)

Question 6

carrying capacity

Answer 6

maximum number of individuals an environment can support

Question 7

carrying capacity is limited by

Answer 7

-intrinsic/density-dependent factors (biotic factors)
-extrinsic/density-independent factors (climate, tillage, herbicides)

Question 8

self-thinning population regulation

Answer 8

death of weakest plants at very high densities (-3/2 power law)

Question 9

fundamental niche

Answer 9

an abstraction of all that a species would require to achieve max growth at both the individual and population levels (does not account for biotic factors)

Question 10

actual niche

Answer 10

what area the species is most likely to experience/live

Question 11

broad niche breadth =
narrow niche breadth =

Answer 11

broad niche breadth = generalist
narrow niche breadth = specialist

Question 12

r-selected species

Answer 12

invest heavily in reproductive effort with high fecundity and short generation time

Question 13

k-selected species

Answer 13

invest more in being competitive (little in reproduction), has low fecundity, and long generation time

Question 14

_____ is the most critical aboveground factor

Answer 14

light

Question 15

factors affecting water uptake/competition

Answer 15

early and rapid root penetration, high root density, high root/shoot ratio, long root hairs

Question 16

species with ______ R* values, the more competitive you are (better survival ability)

Answer 16

lower

Question 17

plant factors affecting competitive ability

Answer 17

height
relative growth rate
net assimilation rate
initial propagule weight/size

Question 18

examples of species with weak competitive ability

Answer 18

green foxtail
chickweed
pineapple weed

Question 19

examples of species with medium competitive ability

Answer 19

wild buckwheat
field bindweed
wild oat
cleavers
lambs quarters
pigweed
wild mustard
kochia
russian thistle

Question 20

examples of species with strong competitive ability

Answer 20

canada thistle
perennial sowthistle
quackgrass
burdock
cocklebur

Question 21

parasitic weeds

Answer 21

infect host plant and extract nutrients from it from either root or stem

Question 22

allelopathy

Answer 22

inhibition of growth or germination by plant toxins