Chapter 39

Question 1

Carolus Linnaeus noted that flowers of different species opened at different times of day and could be used as a _________ or floral clock

Answer 1

horologium florae,

Question 2

A potato left growing in darkness produces shoots that look unhealthy, and it lacks elongated roots
These are morphological adaptations for growing in darkness, collectively called ___________

Answer 2

etiolation

Question 3

After exposure to light, a potato undergoes changes called __________, in which shoots and roots grow normally

Answer 3

de-etiolation (“Greening”)

Question 4

A potato’s response to light is an example of __________

Answer 4

cell-signal processing

Question 5

Internal and external signals are detected by ________, proteins that change in response to specific stimuli

Answer 5

receptors

Question 6

In de-etiolation, the receptor is a _________ capable of detecting light

Answer 6

phytochrome

Question 7

______________ transfer and amplify signals from receptors to proteins that cause responses

Answer 7

Second messengers

Question 8

Two types of second messengers play an important role in de-etiolation: ___________ _______________

Answer 8

Ca2+ ions and cyclic GMP (cGMP)

Question 9

The phytochrome receptor responds to light by ….

Answer 9

Opening Ca2+ channels, which increases Ca2+ levels in the cytosol
Activating an enzyme that produces cyclic GMP

Question 10

De-etiolation activates enzymes that

Answer 10

• Function in photosynthesis directly
• Supply the chemical precursors for chlorophyll production
• Affect the levels of plant hormones that regulate growth

Question 11

Plant hormones are …

Answer 11

chemical signals that modify or control one or more specific physiological processes within a plant

Question 12

Any response resulting in curvature of organs toward or away from a stimulus is called a _________

Answer 12

tropism

Question 13

In the late 1800s, Charles Darwin and his son Francis conducted experiments on __________, a plant’s response to light. They observed that a grass seedling could bend toward light only if the tip of the _______ was present. They postulated that a signal was transmitted from the tip to the __________.

Answer 13

phototropism: coleoptile : elongating region

Question 14

In 1913, Peter Boysen-Jensen demonstrated that the signal was a ____________

Answer 14

mobile chemical substance

Question 15

Plant hormones are produced in very low concentration, but a minute amount can greatly affect ____________ of a plant organ

Answer 15

growth and development

Question 16

In general, hormones control plant growth and development by affecting the _______, ________, and __________ of cells

Answer 16

division, elongation, and differentiation

Question 17

The term auxin refers to any chemical that promotes _____________

Answer 17

elongation of coleoptiles

Question 18

_____________ is a common auxin in plants; in this lecture the term auxin refers specifically to IAA

Answer 18

Indoleacetic acid (IAA)

Question 19

Auxin is produced in ________ and is transported down the stem

Answer 19

shoot tips

Question 20

Auxin transporter proteins move the hormone from the _______________________________

Answer 20

basal end of one cell into the apical end of the neighboring cell

Question 21

Cytokinins are so named because they ________________

Answer 21

stimulate cytokinesis (cell division)

Question 22

_________ are produced in actively growing tissues such as roots, embryos, and fruits

Answer 22

Cytokinins

Question 23

___________ work together with auxin to control cell division and differentiation

Answer 23

Cytokinins

Question 24

Cytokinins, auxin, and strigolactone interact in the control of _____________, a terminal bud’s ability to suppress development of axillary buds
If the terminal bud is removed, plants become bushier

Answer 24

apical dominance

Question 25

Cytokinins slow the aging of some plant organs by inhibiting _____, ______ and_____, and mobilizing nutrients from surrounding tissues

Answer 25

protein breakdown, stimulating RNA and protein synthesis,

Question 26

_________ have a variety of effects, such as stem elongation, fruit growth, and seed germination

Answer 26

Gibberellins

Question 27

The major sites of giberellin production are young roots and leaves. Giberellins are best known for stimulating stem and leaf growth by ____________ and _____________.

Answer 27

enhancing cell elongation and cell division

Question 28

In many plants, both____________ must be present for fruit to develop ____________ are used in spraying of Thompson seedless grapes

Answer 28

auxin and gibberellins: Gibberellins

Question 29

After water is imbibed, release of gibberellins from the embryo signals seeds to ___________

Answer 29

germinate

Question 30

__________ are chemically similar to the sex hormones of animals. They induce cell elongation and division in stem segments. They slow leaf abscission (leaf drops) and promote xylem differentiation.

Answer 30

Brassinosteroids

Question 31

_________ slows growth | Two of the many effects of _______ Seed dormancy and Drought tolerance

Answer 31

Abscisic acid (ABA)

Question 32

Seed________ ensures that the seed will germinate only in optimal conditions

Answer 32

dormancy

Question 33

In some seeds, dormancy is broken when ABA is removed by ______________

Answer 33

heavy rain, light, or prolonged cold

Question 34

___________ germination can be caused by inactive or low levels of ABA

Answer 34

Precocious (early)

Question 35

_______ is the primary internal signal that enables plants to withstand drought

Answer 35

ABA

Question 36

ABA accumulation causes ________to close rapidly

Answer 36

stomata

Question 37

The hormones called ___________ Stimulate seed germination Help establish mycorrhizal associations Help control apical dominance

Answer 37

strigolactones

Question 38

Strigolactones are named for _______ plants

Answer 38

parasitic Striga

Question 39

Striga seeds germinate when host plants exude _________through their roots

Answer 39

strigolactones

Question 40

Plants produce ________ in response to stresses such as drought, flooding, mechanical pressure, injury, and infection. The effects of _________ include response to mechanical stress, senescence, leaf abscission, and fruit ripening

Answer 40

ethylene

Question 41

Ethylene induces the ___________, which allows a growing shoot to avoid obstacles. The ___________ consists of a slowing of stem elongation, a thickening of the stem, and horizontal growth

Answer 41

triple response

Question 42

________ mutants fail to undergo the triple response after exposure to ethylene

Answer 42

Ethylene-insensitive

Question 43

________ is the programmed death of cells or organs

Answer 43

Senescence

Question 44

A burst of ethylene is associated with __________, the programmed destruction of cells, organs, or whole plants

Answer 44

apoptosis

Question 45

A change in the balance of auxin and ethylene controls leaf _________, the process that occurs in autumn when a leaf falls

Answer 45

abscission

Question 46

A burst of ethylene production in a fruit triggers the ________ process which triggers more ethylene. Fruit producers can control _______ by picking green fruit and controlling ethylene levels

Answer 46

ripening

Question 47

Light cues many key events in plant growth and development> Effects of light on plant morphology are called __________

Answer 47

photomorphogenesis

Question 48

A graph called an__________ depicts relative response of a process to different wavelengths: useful in studying any process that depends on light

Answer 48

action spectrum

Question 49

Different plant responses can be mediated by the same or different photoreceptors. There are two major classes of light receptors: _________ and ______________

Answer 49

blue-light photoreceptors and phytochromes

Question 50

Various _________ photoreceptors control hypocotyl elongation, stomatal opening, and phototropism

Answer 50

blue-light

Question 51

__________ are pigments that regulate many of a plant’s responses to light throughout its life These responses include seed germination and shade avoidance

Answer 51

Phytochromes