Midterm 2 - How Plants Work

Question 1

dormancy

Answer 1

• period of no growth and slow metabolic processes

Question 2

abscisic acid

Answer 2

• induces dormancy

Question 3

dormancy-breaking stimuli

Answer 3

• water
• warm temps
• light

Question 4

phytochrome

Answer 4

• plant pigment protein
• 2 reversible forms: Pr and Pfr
• mediates changes in response to light

Question 4

Pr, Pfr

Answer 4

• Pr: absorbs red light, becomes Pfr
• Pfr: absorbs far red light, becomes Pr

Question 5

auxin

Answer 5

• plant hormone
• influences cell elongation, gravitropsim, apical dominance, and root growth

Question 6

cytokinin

Answer 6

• plant hormone
• promotes cell division

Question 7

root-shoot balance

Answer 7

• too much of either is a disadvantage
• too much root: root bound, stunted growth, death
• too much shoot: can’t receive chemical signals

Question 8

suction

Answer 8

• draws water upward from roots to leaves

Question 8

capillarity

Answer 8

• movement of liquid through a narrow space

Question 9

root pressure

Answer 9

• helps drive fluid upward from soil into water-conducting xylem vessels

Question 10

water potential

Answer 10

• potential energy of a water solution per unit volume

Question 11

pressure potential

Answer 11

• positive or negative
• higher pressure = greater potential energy

Question 12

solute potential

Answer 12

• osmotic potential
• negative in plant cell, 0 in distilled water

Question 13

matric potential

Answer 13

• amount of water bound to the matrix or a plant via hydrogen bonds
• negative to 0

Question 14

gravity potential

Answer 14

• negative or 0
• in a plant with no height
• no height = no potential energy

Question 15

water potential gradient

Answer 15

• continuous movement of water relies on it

Question 16

cohesion-tension theory

Answer 16

• as water moves up the plant, it moves down a water potential gradient

Question 17

stomata

Answer 17

• tiny openings on epidermis of leaves
• gaseous exchange
• photsynthesis

Question 18

cell wall bands

Answer 18

• central to growth
• strong but extensible wall

Question 19

high turgour

Answer 19

• optimal form
• plant body in favourable position

Question 20

low turgour

Answer 20

• causes cell to shrink inwards

Question 21

pressure flow model of phloem transport

Answer 21

• high concentration of sugar at the source creates a low solute potential
• low potential draws water into phloem

Question 22

source

Answer 22

• where sugars are
• roots, stems

Question 22

sink

Answer 22

• where sugars end up
• require photosynthate
• roots and young leaves

Question 23

resource partitioning

Answer 23

• division of limited resources

Question 24

tropism

Answer 24

• growth toward or away from stimulus
• adaption to environmental changes

Question 25

positive phototropism

Answer 25

• bending towards light

Question 25

phototropin

Answer 25

• blue-light receptor
• promotes phototropism, stomatal opening and closing, and other responses that promote photosynthesis

Question 26

IAA

Answer 26

• naturally occurring plant hormone of the auxin class

Question 27

expansins

Answer 27

• cell wall proteins
• mediate acid-induced growth

Question 27

positive gravitropism

Answer 27

• growth toward earth’s gravitational center

Question 28

negative gravitropism

Answer 28

• growth away from earth’s gravity

Question 29

thigmotropism

Answer 29

• directional growth of a plant in response to direct contact

Question 30

photoperiod

Answer 30

• regulation of physiology or development in response to day length

Question 31

short-day plants

Answer 31

• need long period of darkness to form flowers

Question 32

long-day plants

Answer 32

• only flowers when light period is longer than a critical length

Question 33

day-neutral plants

Answer 33

• don’t follow restriction of critical duration
• neutral to length of day or night

Question 34

ethylene

Answer 34

• volatile plant hormone
• associated with fruit ripening, flower wilting, and leaf fall

Question 35

senescence

Answer 35

• natural process of aging

Question 36

abscission

Answer 36

• physiological process
• leads to fall of a plant organ