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Biology 9. Plants > Plants 9.3 Growth in plants > Flashcards

Plants 9.3 Growth in plants Flashcards

1
Q

What is determinate growth?

A

animals and some plant organs are either a defined juvenile or embryonic period or growth stops when a certain size is reached or a structure is fully formed

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2
Q

How can growth be indeterminate?

A

when cells continue to divide indefinitely

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3
Q

Do most plants have determinate or indeterminate growth?

A

indeterminate

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4
Q

What phenomenon sets plant cells apart from most animal cells?

A

plants cells (including fully differentiated types) have capacity to generate whole plant called TOTIPOTENT

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5
Q

What does it mean when cells are totipotent

A

plants cells (including fully differentiated types) have capacity to generate whole plant

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6
Q

What are meristems?

A

regions where growth in plants occurs as it is composed of undifferentiated cells undergoing active cell division

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7
Q

What are apical meristems?

A

primary meristems found at tips of stems and roots

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8
Q

Where are shoot apical meristems found?

A

top of the stem

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9
Q

What kinda of meristems do many dicotyledonous plants also develop?

A

Lateral meristems

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10
Q

What do undifferentiated cells in the meristem allow?

A

indeterminate growth

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11
Q

How do cells in meristems produce more cells?

A

by dividing by mitosis and cytokineses

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12
Q

What is the root apical meristem responsible for?

A

growth of the root

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13
Q

What do shoot apical meristems produce?

A

throws off the cells that are needed for growth and produces cells that grow leaves and flowers

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14
Q

What type of meristems can be found in plants?

A

apical and lateral

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15
Q

How does the differentiation of meristem cells cause the growth of the plant?

A

For each division, one cell remains in the meristem while the other one grows in size and is pushed away from th region

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16
Q

What kinda of meristems can apical meristems produce?

A

protoderm, procambium and ground meristem

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17
Q

what tissue does protoderm produce?

A

epidermis

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18
Q

What tissue does procambium produce?

A

vascular tissues

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19
Q

What tissus does ground meristem produce?

A

pith

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20
Q

What is leaf primordia?

A

Small bumps at the side of shoot apical meristem that will develop into leaves

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21
Q

What is this called?

A

leaf primordia

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22
Q

What controls the growth in shoot appex?

A

Plant hormones

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23
Q

What is hormone?

A

chemical message produced and released in one part of an organism to affect another part

24
Q

What are auxins?

A

hormones that can initiate growth of roots, influence development of fruits and regulating leaf development

25
What is the most abundant auxin?
IAA
26
What role does IAA have?
controls growth in shoot apex; promotes elongation of cells in stems
27
Where is IAA synthesized
in the apical meristem of the shoot and transported down the stem to stimulate growth
28
What can high concentrations if IAA cause?
it can inhibit growth at nodes
29
What are axillary buds?
shoots that form the junction/node of the stem and base of a leaf
30
What is apical dominance?
As shoot apical meristem grows and forms leaves, regions of meristem are left behind at the nodes. Growth at nodes is inhibited by auxin
31
What happens when the further distant a node is from the shoot apical meristem?
lower concentration of auxin and the less likely that growth in the axillary bud will be inhibited by auxin
32
What is ahormone produced in the root of plants?
cytokinins
33
What does cytokinin promote?
axillary bud growth
34
What balance determines the axillary bud develops?
ratio of cytokinin and auxins
35
What influences the direction in which a stem grows?
light and gravity
36
How does light affect stem's growth?
grows towards source of brightest light
37
How do stems grow in absence of light?
upwards/opposite gravity
38
What is tropisms?
directional growth responses to directional external stimuli
39
What is growth towards the light called?
phototropism
40
What is growth in response to gravitational force called?
gravitropism
41
what is the first stage in phototropism?
absorption of light by photoreceptors using phototroponins
42
What do phototroponins do?
absorption of light of an appropriate wavelength by photoreceptors that changes conformation; bind to receptors within cell that control transcription; that codes a group of glycoproteins
43
How does auxin influence cell growth rates?
changing patterns of gene expression
44
What protein transports auxin?
PIN3
45
What happens if phototropins detects greater intensity of light on one side?
auxin is transported to the shaded side; higher concentration of auxin on the shadier side causes cell elongation (greater growth on oneside); stem grows in a curve towards source of light; leaves can recieve more light and photosynthesize at greater rate
46
Is gravitropism auxin dependent?
yes
47
What are cellular orgenelles called that accumulate on the lower side of cells in roots?
statoliths
48
If a plant is tipped over, what happens?
statoliths accumulate on lower side of cells; PIN3 transporter proteins distribute and direct auxin transport to the bottom cells (closer to earth core); high concentration of auxin IN ROOTS inhibits growth, so top cells elongate; root bends downwards
49
In shoot (stems) what does high concentration of auxin cause?
promotes elongation of cells
50
In roots what does high concentration of auxin cause?
inhibits elongation of cells, top cells elongate
51
Explain role of auxin in phototropism
* auxin is plant hormone * produced by the tip the stem/shoot tip * causes transportation of hydrogen ions from cytoplasm to cell wall * decrease in pH/H+ pumping breaks bonds between cell wall fibres * makes cell walls flexible/extnsible/softens cell walls * auxin promotes cell elongation/growth * gene expression also altered by auxin to promote cell growth * positive phototropism is growth towards light * shoot tip senses direction of (brightest) light * auxin moved to side of stem with least light/dark side * causes cells on dark side to elongate/cells on dark side grow faster
52
What is micropropagation?
*in vitro* procedure that produces large numbers of identical plants
53
What does micropropagation depend on?
totipotentency of plant tissues (ability to differentiate into any functional plant part)
54
Describe process of micropropagation of plants
* stock plant is identified that often has desirable feature * tissue is chosen usually the least differentiated (meristem) * tissues from plant is sterilized and cut into pieces called **explant**s * explant is placed into sterilized growth media that includes plant hormones * auxin and cytokinin is equally added * forms an undifferented mass called **callus** * if media contains a ratio of auxin 10 times greater than cytokinin roots develop * this is called **rooting media** * if media contains ratio of cytokinin 10times greater, then shoots develop * this is called **shoot media**
55
Why are micropropagation techniques used?
* international exchange of plants materials carries risk of pathogen transmission * micropropagation produces virus-free strains of plants * produces identical copies of desirable characteristics * process is fast and takes little space * can help preserve endangered varieties (eg. orchids) * commerical production * orchid seeds are difficult to germinate
56
How are apical meristems virus-free?
Viruses are transported within a plant from cell to cell through vascular tissue and via **plasmodesmata**
57
What is cryopreservation?
micropropagated plantlets can be stored in liquid nitrogen

Biology 9. Plants (6 decks)

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