Bio Ch 26 Flashcards
Signal Transduction
plants respond to stimuli by utilizing this; the binding of a molecular signal that initiates and amplifies a cellular response
Receptors
proteins activated by a specific signal
Transduction pathway
series of relay proteins or enzymes that amplify and transform the signal to one understood by the machinery of the cell
Cellular Response
the result of the transduction pathway; brings about the observed macroscopic response (ex. stomata closing or a stem that turns toward the light)
Hormones
chemical messenger produced in one part of the body that controls the activity of other parts
Auxins
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)
Apical dominance
occurs when the terminal bud produces new growth instead of the axillary buds
Coleoptile
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
Gibberellins
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
Dormancy
period of time when plant growth is suspended; gibberellins is one way to break this
Cytokinins
derivatives of adenine, one of the purine bases in DNA and RNA
Senescence
when a plant organ, such as a leaf, loses its natural color, it is most likely undergoing an aging process called this
Abscisic Acid (ABA)
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
Abscission
the dropping of leaves, fruits, and flowers from a plant
Ethylene
CH2; gas formed from the amino acid methionine; this hormone is involved in abscission and the ripening of fruits
Tropism
growth toward or away from a unidirectional stimulus
Gravitropism
growth response of roots and stems of plants to the Earth’s gravity; roots demonstrate positive gravitropism, and stems demonstrate negative gravitropism
Statoliths
root cap cells contain sensors called this, which are starch grains located within amyloplasts, a type of plastid
Phototropism
growth of plant stems to light; stems demonstrate positive _______
Thigmotropism
unequal growth due to contact with solid objects; ex. coiling of tendrils or the stems of plants (ex. peas, morning glory plants)
Turgor Movements (Nastic movements)
in plant cells, pressure of the cell contents against the cell wall when the central vacuole is full
Circadian rhythms
activities that regularly occur in a 24-hour cycle, such as sleep movements; ex. prayer plant (leaves fold upward at night), morning glory
Biological clock
internal mechanism by which a circadian rhythm is maintained in the absence of appropriate environmental stimuli
Photoperiod
length of daylight compared to the length of darkness; sets the biological clock
