Deck 6: Plant Senescence

Question 1

Glyceraldehyde 3-phosphate,the three-carbon precursor to the sugar glucose,is formed in the light phase of photosynthesis.

Answer 1

False

Question 2

Postembryonic cellular proliferation in plants occurs exclusively in the:
(a)apical meristem.
(b)lateral shoots.
(c)roots.
(d)xylem.

Answer 2

A

Question 3

Which of the following processes is not involved in proliferative senescence?
(a)oxidative damage
(b)membrane dysfunction
(c)chlorophyll degradation
(d)telomere shortening

Answer 3

D

Question 4

Which of the following best describes plant senescence?
(a)Plant senescence is a by-product of genes selected for reproductive success.
(b)Plant senescence is largely a random,stochastic event.
(c)Plant senescence is an intrinsic part of the reproductive and development function of plants.
(d)Only 3-4% of the plant genome participates in senescence.

Question 5

The age-related,regulated dismantling of plant cells is referred to as ______ senescence.
(a)planned
(b)programmed
(c)timed
(d)stochastic

Question 6

Photosynthesis occurs in the chloroplasts.

Question 7

Which of the following best matches the definition "a woody vascular system made up of dead cells"?

A)vacuole
B)xylem
C)tonoplast
D)phloem

Question 8

The process of leaf senescence can be described in three phases:
(a)initiation,elongation,and termination.
(b)budding,degradation,and termination.
(c)initiation,degradation,and termination.
(d)start,middle,and end.

Question 9

Plant hormones are synthesized only by a specialized group of cells called the apical meristem.

Question 10

During ______ senescence,the nuclear and vacuolar membranes break down and release their contents into the cytosol;much of the released material is toxic to the remaining cytosolic structures.
(a)planned
(b)programmed
(c)stochastic
(d)timed

Question 11

True or false: The beginning of plant senescence is generally thought to be a decline in photosynthesis.

Question 12

Which type of plastids store pigments other than chlorophyll?
(a)leucoplasts
(b)mitochondria
(c)phloem
(d)chromoplasts
The Biology of Plant Senescence

Question 13

Select the correct order of the three steps in the Calvin cycle.
(a)carboxylation,regeneration,reduction
(b)regeneration,carboxylation,reduction
(c)carboxylation,reduction,regeneration
(d)reduction,regeneration,carboxylation

Question 14

Short-answer question: In one or two sentences,explain the differences between plants' proliferative senescence and animals' replicative senescence.

Question 15

Plants do not use the same general scheme of transcription,translation,cellular transport,and energy production as animals.

Question 16

Short-answer question: Define source and sink metabolism in plants.

Question 17

Plant cells can be distinguished from animal cells by three unique structures,which include all of the following except:
(a)plastids.
(b)cell walls.
(c)smooth endoplasmic reticulum.
(d)central vacuole.

Question 18

True or false: A monocarpic plant undergoes many seasons of growth and proliferative senescence.

Question 19

The laws governing the ratio of energy requirements to size,known as ______ scaling,limit the size that a plant cell can attain and still function efficiently.

Question 20

Plant cells communicate and exchange molecules with each other through small tunnel-like structures in the primary cell wall that are called:
(a)plasmodesmata.
(b)smooth endoplasmic reticulum.
(c)plastids.
(d)central vacuoles.

Question 21

Which plant is most often used as the model for describing plant senescence?
(a)Larrea tridentata
(b)Populus tremuloides
(c)Arabidopsis thaliana
(d)Zea mays

Question 22

The phytol tail of chlorophyll is used in the synthesis of which vitamin?

A)vitamin D
B)vitamin A
C)vitamin C
D)vitamin E

Question 23

Senescence-related membrane degradation starts in the:
(a)cell membrane.
(b)tonoplast.
(c)chloroplast.
(d)mitochondria.

Question 24

The accumulation of glucose in leaf cells during the early stages of programmed senescence most likely reflects which two factors?
(a)absence of sucrose production;increase in photosynthesis
(b)decrease in photosynthesis;export of sucrose from the cell
(c)absence of sucrose production;release of glucose from intracellular starch stores
(d)release of glucose from intracellular starch stores;increase in photosynthesis

Question 25

Fill in the blank: The bending of a plant toward light is called ______.

Question 26

True or false: The products of chlorophyll catabolism formed during plant senescence are reused for chlorophyll synthesis.

Question 27

True or false: The process of senescence-related membrane degradation is identical in all membranes regardless of the cellular structure involved.

Question 28

Which part of the light spectrum has the greater effect on photosynthesis?
(a)far-red
(b)blue
(c)far-blue
(d)red

Question 29

Fill in the blank: During programmed senescence,leaf cells rely on ______ as their energy reserve for metabolic activity.

Question 30

The senescent cell must turn to external sources of glucose late in the programmed senescence phase to finish the dismantling process.This glucose seems to be derived from the:
(a)plasmodesmata.
(b)phloem.
(c)xylem.
(d)tonoplast.

Question 31

Short-answer question: Briefly explain why the loss in a membrane's selective permeability results in rupture of the membrane.

Question 32

True or false: The overwhelming majority of the mRNA expressed in the senescent leaf codes for proteases,lipases,and nucleases.

Question 33

True or false: Declining photosynthesis is the primary event that initiates plant senescence.

Question 34

True or false: The senescence-related degradation of the chloroplast and/or chlorophyll shifts the gene expression profile to genes needed for sucrose synthesis.

Question 35

The metabolites of chlorophyll catabolism are mainly stored in the:
(a)mitochondria.
(b)vacuole.
(c)plasmids.
(d)cytosol.

Question 36

True or false: Stress,like disease in animals,makes plants more susceptible to increased rates of aging and limited longevity,but it does not reflect the underlying mechanism of aging and longevity.

Question 37

True or false: One process by which glucose and fructose enter a plant cell during programmed senescence is apoplastic uploading.

Question 38

The three factors that seem to have the most influence on non-stress-related plant senescence are:
(a)light intensity,amount of light,and plant hormones.
(b)light intensity,atmosphere,and plant hormones.
(c)light intensity,amount of light,and predation.
(d)light intensity,water content,and predation.

Question 39

The degradation of stromal membranes releases the ______ contents into the cytosol and initiates the expression of proteases and lipases targeted at the membranes of other organelles.
(a)cytosol
(b)lysozyme
(c)mitochondrial
(d)chloroplast
Initiating Plant Senescence

Question 40

The chloroplast contains approximately 75% of the proteins found in photosynthetically active leaf cells.The breakdown of these proteins to free amino acids is an important source of ______ that is exported from the cell during programmed senescence.
(a)nitrogen
(b)carbohydrate
(c)magnesium
(d)protein

Question 41

True or false: The cytokinin signaling pathway affects the cells of the apical meristem,seed development,chloroplast biosynthesis,and several other growth and development processes.

Question 42

Short-answer question: Briefly explain how a decrease in the ratio of red to far-red light may initiate plant senescence.

Question 43

Which plant hormone is most important to fruit ripening?
(a)abscisic acid
(b)cytokinin
(c)ethylene
(d)jasmonic acid

Question 44

Cytokinins,a class of phytohormones,function primarily as ______ regulators in young plants.
(a)cell membrane
(b)replication
(c)growth
(d)gene

Question 45

Compared with far-red light,red light induces ______ photosynthetic activity.

A)more
B)less
C)slightly less
D)the same

Question 46

Biosynthesis of cytokinins occurs in all plant tissues and seems to be regulated by ______ concentration.
(a)glucose
(b)ATP
(c)protein
(d)nitrogen

Question 47

True or false: Jasmonic acids are noted for their response to wounds in plants.

Question 48

______ concentration increases or remains stable as the cellular levels of nitrogen from protein degradation increase during the early phase of programmed senescence.
(a)Salicylic acid
(b)Jasmonic acid
(c)Abscisic acid
(d)Cytokinin

Question 49

True or false: Abscisic acid induces closure of the stomata in response to drought conditions.

Question 50

Molecular analysis indicates that many genes associated with ethylene biosynthesis are ______ during senescence.
(a)down-regulated
(b)silenced
(c)mutated
(d)up-regulated