Bio Ch 26 Flashcards

1
Q

Signal Transduction

A

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

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2
Q

Receptors

A

proteins activated by a specific signal

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3
Q

Transduction pathway

A

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

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4
Q

Cellular Response

A

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

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5
Q

Hormones

A

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

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6
Q

Auxins

A

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)

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7
Q

Apical dominance

A

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

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8
Q

Coleoptile

A

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

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9
Q

Gibberellins

A

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

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10
Q

Dormancy

A

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

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11
Q

Cytokinins

A

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

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12
Q

Senescence

A

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

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13
Q

Abscisic Acid (ABA)

A

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

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14
Q

Abscission

A

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

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15
Q

Ethylene

A

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

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16
Q

Tropism

A

growth toward or away from a unidirectional stimulus

17
Q

Gravitropism

A

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

18
Q

Statoliths

A

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

19
Q

Phototropism

A

growth of plant stems to light; stems demonstrate positive _______

20
Q

Thigmotropism

A

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

21
Q

Turgor Movements (Nastic movements)

A

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

22
Q

Circadian rhythms

A

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

23
Q

Biological clock

A

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

24
Q

Photoperiod

A

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

25
Q

Photoperiodism

A

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

26
Q

Phytochrome

A

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

27
Q

Etiolate

A

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

28
Q

Short-day plants

A

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

29
Q

Long-day plants

A

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

30
Q

Day-neutral plants

A

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

31
Q

Secondary metabolites

A

plants produce these molecules as a defense mechanism

32
Q

Alkaloids

A

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

33
Q

Cyanogenic glycosides

A

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

34
Q

Systemin

A

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

35
Q

Hypersensitive response (HR)

A

seals off the infected area and also initiates the wound response