Lecture 15: The Mechanism of Plant Growth

Question 1

are cell division and growth the same thinng

Answer 1

NO! cell division doesnt always mean growth occurs

Question 2

The plant cell cycle=

Answer 2

complex!

–> G1 –> S –> G2 –> M –>

Question 3

what are the building blocks for growth

Answer 3

meristems

Question 4

orientation of cell division dictates

Answer 4

the architecture of the tissue

Question 5

plants cell generate an internal _____ via vacuole expansion

Answer 5

hydrostatic pressure (turgor) 
The outward acting force is resisted by the rigidity of the cell wall.

Question 6

The plant cell wall is a complex polymer of

Answer 6

Carbohydrates. The polymers proceed biophysical strength to the wall

Question 7

cellulose:

Answer 7

long, unbranched glucose polymer

Question 8

Hemi-cellulose:

Answer 8

Branched glucose-based polymer

Question 9

Pectin:

Answer 9

highly branches glucoronic acid-based polymer

Question 10

build up structure of the leaf:

Answer 10

Beta Glucose monomer –> Cellulose molecules –> microfibril –> Cellulose microfibrils in a plant cell wall –> plant cells –> LEAF

Question 11

growth occurs os controlled by the

Answer 11

extensibility of the cell wall

Question 12

cell wall extensibility is controlled by

Answer 12

protein factor s and pHpH is controlled by hormones (e.g. auxin)

Question 13

the expression of genes encoding the cell wall proteins is controlled by

Answer 13

endogenous & exogenous factors. Again, plant development is an integration of pre-programmedevents & specific environmental triggers

Question 14

The orientation of cellulose microfibrils controls the

Answer 14

direction of cell growth

Question 15

the orientation of cellulose microfibril synthesis is guided by the

Answer 15

cell cytoskeleton

Question 16

controlled loosening of the cell wall allows

Answer 16

growth
•The direction of cell growth is controlled by the orientation of cellulose microfibrils.
•The orientation of cellulose microfibrils is controlled by the cytoskeleton.

Question 17

plant hormones ____ growth

Answer 17

influence

Question 18

plant hormones:

Answer 18

Auxin, Cytokinin,
Gibberellin, Abscisic acid,
Ethylene, Brassinosteroid

Question 19

Auxin =

Answer 19

growth promoting, promote cell division

Question 20

cytokinin =

Answer 20

promote cell division, inhibit senescence

Question 21

Gibberellin =

Answer 21

growth promoting, promote seed germination

Question 22

Abscisic acid =

Answer 22

inhibit growth, promote senescence

Question 23

Ethylene =

Answer 23

inhibit growth, promote fruit ripening

Question 24

Brassinosteroids =

Answer 24

inhibit growth

Question 25

hormones (growth factors) act like

Answer 25

‘switches’
A switch can (in theory) be linked with any output.
Since all organisms evolve from other organisms, the context of a switch tends to be conserved

Question 26

concept of ‘ ___’ in development

Answer 26

bricolage = construction from a wide range of available things

Question 27

Gibberellin acid =

Answer 27

induces growth, used to promote growth in seedless grapes

Question 28

intake of water leads to gibberellin acid ____

Answer 28

synthesis.
This induces the expression of genes for amlyase. Amylase is required for starch breakdown to release sugars for germination (and beer!)

Question 29

one hormone can have ___ affects

Answer 29

different

- depending on context

Question 30

the polar stream of auxin controls many processes in plants:

Answer 30

• axillary bud outgrowth
• vascular differentiation
• leaf formation

Question 31

Downward flux of auxin inhibits

Answer 31

axillary meristem.

Damage to source of auxin allows axillary meristem activation & growth

Question 32

Auxin flux leads to a local

Answer 32

high auxin level which determines where the

root stem cells form

Question 33

plant growth is ___ to the environment

Answer 33

responsive

• light (phototropism)
• gravity (gravitropism)
• physical touch (thigmotropism)