Plant structure & growth 2

Question 1

What is the general role of meristems?

Answer 1

Generating cells for primary + secondary growth

Question 2

What type of tissue are meristems?

What are the 2 types of meristems?

Answer 2

Embryonic tissue

Apical & lateral

Question 3

What does secondary growth cause?

Answer 3

Increase in diameter of stems + roots in woody plants

Question 4

Where in a woody plant does secondary growth occur?

Answer 4

Stems & roots

- rarely leaves

Question 5

What does the secondary plant body consist of?

Answer 5

The tissues produced by the vascular cambium + cork cambium

Question 6

What type of plant is secondary growth a characteristic of?

Answer 6

Gymnosperms & many eudicots

- NOT monocots

Question 7

What happens when primary growth from apical meristems nears completion?

Answer 7

Vascular cambium forms

Question 8

What happens during 1st year of secondary growth in the vascular cambium?

Answer 8

> Secondary xylem & phloem thicken the stem
Vascular rays form
Cork cambium develops from parenchyma cells + produces cork

Question 9

What happens to cells external to the cambium during secondary growth?

Answer 9

Cells (including epidermis) cannot divide so rupture

Question 10

What are vascular rays?

Answer 10

Radial files of parenchyma

- connects secondary xylem + phloem for nutrient + water movement and repair

Question 11

What happens in the 2nd year of secondary growth?

Answer 11

Secondary growth in secondary xylem, phloem & cork

Question 12

What is bark?

Answer 12

All tissue exterior to vascular cambium

Question 13

What does developmental plasticity describe?

Give an example

Answer 13

The effect of environment on development

Cabomba caroliniana forms diff leaves depending on whether or not apical meristem is submerged

• feathery leaves underwater reduces resistance to moving water
• pads on surface to aid flotation

Question 14

What does development consist of?

Define the components

Answer 14

> Growth = irreversible increase in size
Morphogenesis = development of body form & organisation
Cell differentiation = process by which cells w/ same genes become diff from each other

Question 15

What are the 2 components of growth?

Answer 15

Cell division

Cell expansion

Question 16

What does cell division in meristems do?

What is cell expansion accountable for

Answer 16

Increases cell no. + the potential for growth

Actual increase in plant size

Question 17

In what plane do new cell walls form?

Answer 17

Perpendicular to main axis of cell expansion

Question 18

When is the plane in which a cell divides determined?

How is it predicted?

Answer 18

During late interphase

Microtubules become concentrated into a ring (=preprophase band) that predicts the future of cell division

Question 19

Leaf growth results fro m a combination of what?

Answer 19

Transverse + longitudinal cell divisions

Question 20

It has long been thought that leaf form is determined by what?

Answer 20

Plane of cell division

Question 21

What does a mutation in the tangled-1 gene in maize do?

Answer 21

Affects longitudinal divisions BUT doesn’t affect leaf shape

Mutant leaves grow slower

Question 22

What determines cell fate?

Answer 22

The symmetry of cell division

= distribution of cytoplasm between daughter cells

Question 23

Give an example of asymmetrical cell division

Answer 23

Asymmetrical cell division and change in plane of cell division in the formation of guard cells

Question 24

What do asymmetrical cell division play a role in?

Answer 24

Establishing polarity

- critical step in plant morphogenesis

Question 25

What is polarity?

Answer 25

The condition of having structural or chemical differences at opposite ends of an org e.g. plants have roots + shoots

Question 26

Describe the 1st division of a plant zygote

Answer 26

>Asymmetrical | >Initiates polarisation into root + shoot

Question 27

How are gnom mutants of Aridopsis different to normal plants?

Answer 27

>Result from a symmetrical 1st division >Have no leaves or roots > Defect traced to an inability to transport auxin in a polar manner

Question 28

How is the expansion of plant cells different to animal cells?

Answer 28

Animals: synthesise protein-rich cytoplasm (metabolically expensive) Plants: grow rapidly at lower energy cost by storage of water in vacuoles - only 10% is by synthesis of cytoplasm

Question 29

In what plane do plant cells expand primarily?

Answer 29

Along plant's main axis | - shoot + root

Question 30

What does the orientation of cellulose microfibrils in the cell wall cause? How?

Answer 30

Restricts direction of cell elongation - microfibrils don't stretch so cell expands perpendicular to their orientation - enzymes weaken cross-links allowing more expansion

Question 31

What is pattern formation?

Answer 31

Development of specific structures in precise locations

Question 32

What are the 2 hypotheses to explain the fate of plant cells?

Answer 32

Lineage-based = cell fate is determined early in development + is passed on to progeny cells Position-based = cell fate is determined by final position in an emerging organ

Question 33

What do laser ablation experiments suggest about plant cell fate? How does this compare to animal cells?

Answer 33

Cell fate is established late in development + depends on signalling from neighbouring cells Cells are largely lineage-dependent

Question 34

Describe how positional info is conveyed by cell-to-cell communication in Arabidopsis root epidermis. What does this result in?

Answer 34

Epidermal cell boarding single cortical cell expresses GLABRA-2 = hairless Epidermal cell boarding 2 cortical cells doesn't express GLABRA-2 = develops a root hair

Question 35

What does flower formation involve?

Answer 35

A phase change from vegetative growth to reproductive growth - associated w/ switching on of floral meristem identity genes

Question 36

What is flower formation triggered by?

Answer 36

Combination of enviro cues (e.g. day length) + internal signals (e.g. hormones)

Question 37

What are the organ identity gens that regulate the development of floral pattern known as?

Answer 37

MADS-box genes

Question 38

Which organ develops where only A genes are expressed? What about A + B genes? What about B + C genes? What about only C genes?

Answer 38

Sepals Petals Stamens Carpels