Lecture 6 - Seed Banks

Question 1

what is evolutionary fitness dependent on

Answer 1

adaptive responses
sensory systems
environmental cues (information)

Question 2

seeds

Answer 2

units of reproduction, dispersal in space, and dispersal in time

Question 3

seeds can detect light through ________

Answer 3

photoreceptors

Question 4

2 types of photoreceptors in seeds

Answer 4

phytochromes (red light)
cryptochromes (blue light)

Question 5

photo-sensitive pigments enable the seed to sense the presence of ________

Answer 5

empty gaps

Question 6

gap sensing

Answer 6

no gap - shadow (low light intensity and quality)
gap - light (higher light intensity and quality)

Question 7

conditions favorable for weed seed germination

Answer 7

-exposure to light
-aerobic conditions
-essential nutrients should be available in the soil
-optimal soil temp
-optimal soil moisture

Question 8

seed bank

Answer 8

seeds are shed and incorporated into the soil and some seeds retain viability

Question 9

why do some seeds lose viability

Answer 9

failed germination
physiological deterioration
herbivory or pathogenesis
adverse soil conditions

Question 10

seed longevity in the soil is _________

Answer 10

species specific

Question 11

non-dormant

Answer 11

a state in which germination will occur if conditions are favorable

Question 12

dormant

Answer 12

physiological conditions wherein seeds do not germinate even though conditions are favorable

Question 13

quiescent

Answer 13

non-dormant but prevented from germination due to unfavorable conditions (enforced dormancy)

Question 14

types of seed dormancy

Answer 14

physiological seed dormancy
physical seed dormancy
morphological seed dormancy
morphophysiological seed dormancy
combinational seed dormancy

Question 15

physiological seed dormancy

Answer 15

physiological mechanism in embryo prevents radicle emergence using hormones ABA:GA ratio (broken by temp changes, light exposure, etc)

Question 16

physical seed dormancy

Answer 16

seed coat characteristics where seed coat is often impermeable to water and needs scarification to germinate

Question 17

morphological seed dormancy

Answer 17

underdeveloped embryo where it finishes development after seed dispersal

Question 18

morphophysiological seed dormancy

Answer 18

seeds have underdeveloped embryo and physiological component to dormancy (requires dormancy-breaking treatment)

Question 19

combinational seed dormancy

Answer 19

seeds have impermeable coats (physical) but also have physiological dormancy

Question 20

primary dormancy

Answer 20

passes through this stage only once. Dormancy is present at maturity on mother plant (often due to underdeveloped embryo)

Question 21

secondary dormancy

Answer 21

secondary in time. Occurs after seed has gone through a non-dormant period (often a type of physiological dormancy driven by hormones)

Question 22

after-ripening

Answer 22

seeds gradually acquire the ability to germinate over wide conditions (biochemical changes)

Question 23

transient

Answer 23

can only stay in seed bank for 1 yr

Question 24

persistent seed bank

Answer 24

seed stays in the soil for 1 or more years (most ag weeds)

Question 25

degrees of secondary dormancy

Answer 25

-non-dormant -conditionally dormant -dormant

Question 26

non-dormant secondary dormancy

Answer 26

seed germinates over widest range of environmental conditions highly sensitive to environment and hormones

Question 27

conditionally dormant secondary dormancy

Answer 27

seed germinates over narrow range of environmental conditions less sensitive to environmental and hormonal factors

Question 28

dormant secondary dormancy

Answer 28

seed cycles through secondary dormancy from non-dormant to dormant insensitive to environmental and hormonals

Question 29

factors that induce dormancy

Answer 29

temperature, low oxygen, light quality (low R:FR), darkness

Question 30

low red: far red ratio induces _________ response

Answer 30

shade-avoidance

Question 31

dormancy breaking requirements

Answer 31

temp (hot, cold, or fluctuating) exposure to light sufficient levels of oxygen high nitrate concentrations water

Question 32

safe microsites should provide...

Answer 32

light, aerobic conditions essential nutrients optimal soil temp optimal soil moisture protection from natural enemies

Question 33

what does seed longevity in the soil depend on

Answer 33

species seed physical and chemical characteristics soil conditions environmental conditions biotic activity

Question 34

how do soil seed banks form

Answer 34

-animals (vertebrates and invertebrates) -tillage -natural seed movement

Question 35

fate of seed banks

Answer 35

germinate dormancy state can change (primary to secondary) Dormancy continuum Die due to aging/predators/pathogens

Question 36

requirements of germination

Answer 36

- viable, non-dormant seed - conditions necessary for germination -conditions necessary for emergence

Question 37

microsite

Answer 37

a site where dormancy could be broken and that had necessary conditions for germination and emergence