Bio Ch 26

Question 1

Signal Transduction

Answer 1

plants respond to stimuli by utilizing this; the binding of a molecular signal that initiates and amplifies a cellular response

Question 2

Receptors

Answer 2

proteins activated by a specific signal

Question 3

Transduction pathway

Answer 3

series of relay proteins or enzymes that amplify and transform the signal to one understood by the machinery of the cell

Question 4

Cellular Response

Answer 4

the result of the transduction pathway; brings about the observed macroscopic response (ex. stomata closing or a stem that turns toward the light)

Question 5

Hormones

Answer 5

chemical messenger produced in one part of the body that controls the activity of other parts

Question 6

Auxins

Answer 6

produced in shoot apical meristem and are found in young leaves and in flowers and fruits; most common naturally occurring one of these is indoleacetic acid (IAA)

Question 7

Apical dominance

Answer 7

occurs when the terminal bud produces new growth instead of the axillary buds

Question 8

Coleoptile

Answer 8

protective sheath for the young leaves of the seedling; Charles Darwin and son Francis found that phototropism does not occur if the tip of the seedling is cut off or covered by a black cap; 1926 - Frits Went - agar block experiment - coined term auxin

Question 9

Gibberellins

Answer 9

there are 70 of these that we know of; most common is GA3; promote stem elongation; discovered in 1926; Eiichi Kurosawa was investigating a fungal disease of rice plants called “foolish seedling disease”; he coined this term, named after the fungus _____ fujikuroi; sources in flowering plant parts are young leaves, roots, embryos, seeds, and fruits

Question 10

Dormancy

Answer 10

period of time when plant growth is suspended; gibberellins is one way to break this

Question 11

Cytokinins

Answer 11

derivatives of adenine, one of the purine bases in DNA and RNA

Question 12

Senescence

Answer 12

when a plant organ, such as a leaf, loses its natural color, it is most likely undergoing an aging process called this

Question 13

Abscisic Acid (ABA)

Answer 13

produced by any green tissue that contains chloroplasts; also produced in monocot endosperm and roots where it is derived from carotenoid pigments; sometimes called the stress hormone b/c it initiates and maintains seed and bud dormancy and brings about the closure of stomata

Question 14

Abscission

Answer 14

the dropping of leaves, fruits, and flowers from a plant

Question 15

Ethylene

Answer 15

CH2; gas formed from the amino acid methionine; this hormone is involved in abscission and the ripening of fruits

Question 16

Tropism

Answer 16

growth toward or away from a unidirectional stimulus

Question 17

Gravitropism

Answer 17

growth response of roots and stems of plants to the Earth’s gravity; roots demonstrate positive gravitropism, and stems demonstrate negative gravitropism

Question 18

Statoliths

Answer 18

root cap cells contain sensors called this, which are starch grains located within amyloplasts, a type of plastid

Question 19

Phototropism

Answer 19

growth of plant stems to light; stems demonstrate positive _______

Question 20

Thigmotropism

Answer 20

unequal growth due to contact with solid objects; ex. coiling of tendrils or the stems of plants (ex. peas, morning glory plants)

Question 21

Turgor Movements (Nastic movements)

Answer 21

in plant cells, pressure of the cell contents against the cell wall when the central vacuole is full

Question 22

Circadian rhythms

Answer 22

activities that regularly occur in a 24-hour cycle, such as sleep movements; ex. prayer plant (leaves fold upward at night), morning glory

Question 23

Biological clock

Answer 23

internal mechanism by which a circadian rhythm is maintained in the absence of appropriate environmental stimuli

Question 24

Photoperiod

Answer 24

length of daylight compared to the length of darkness; sets the biological clock

Question 25

Photoperiodism

Answer 25

a physiological response prompted by changes in the length of day or night in a 24-hour daily cycle; influences flowering in some plants

Question 26

Phytochrome

Answer 26

blue-green leaf pigment that is present in the cytoplasm of plant cells; composed of 2 identical proteins; each protein has a larger protein in which a light-sensitive region is located; smaller portion is a kinase that can link light absorption with a transduction pathway within the cytoplasm

Question 27

Etiolate

Answer 27

seedlings that are grown in the dark do this; shoot increases in length and the leaves remain small

Question 28

Short-day plants

Answer 28

flower when the day length is shorter than a critical length (cocklebur, goldenrod, poinsettia, chrysanthemum)

Question 29

Long-day plants

Answer 29

flower when the day length is longer than a critical length; (wheat, barley, rose, iris, clover, spinach)

Question 30

Day-neutral plants

Answer 30

not dependent on day length for flowering; (tomato, cucumber)

Question 31

Secondary metabolites

Answer 31

plants produce these molecules as a defense mechanism

Question 32

Alkaloids

Answer 32

bitter nitrogenous substances; a secondary metabolite; ex. morphine, nicotine, caffeine (block DNA and RNA synthesis)

Question 33

Cyanogenic glycosides

Answer 33

secondary metabolite; a molecule containing a sugar group; breaks down to cyanide and inhibits cellular respiration (ex. digitalis, taxol)

Question 34

Systemin

Answer 34

in plants, an 18-amino-acid peptide that is produced by damaged or injured leaves that leads to the wound response

Question 35

Hypersensitive response (HR)

Answer 35

seals off the infected area and also initiates the wound response