Plant Growth And Development

Question 1

What is plant growth and development limited by?

Answer 1

• disease
• environment (drought, fires, frost)
• own success (May be too large to supply all nutrients)

Question 2

Why is plant growth indeterminate?

Answer 2

Indeterminate growth means it does not terminate.

Plants are said to have indeterminate growth because they contain perpetually dividing stem cells in the meristem.

Question 3

What are totipotent cells and where are they located in plants?

Answer 3

Totipotent cells are differentiate into any plant part. They are located in root and shoot meristems which contain perpetually dividing embryonic stem cells.

Question 4

What type of cells are used in the cloning of plant culture?

Answer 4

Meristem cells as they contain totipotent cells that can differentiate into any plant part.

Question 5

Where does the growth and development of new organs in the plant occur and what is the function of cells in this region?

Answer 5

Begins in the apical meristems at the tips of the root and shoot. The function of cells in the meristem is to divide.

Question 6

What does the apical meristem at roots and shoots leave behind?

Answer 6

It leaves behind tissue to mature, replacing themselves with more embryonic cells.

Question 7

Describe the structure of the root apical meristem.

Answer 7

• protected by root cap as it grows through the soil

- covered in hairs that maximise surface area to allow better absorption of soil

Question 8

Describe the function and structure of the shoot apical meristem.

Answer 8

Function: produces stems and leaves, and flowers when plant enters its reproductive phase.

• apex of the shoot is a dome of meristematic cells
• this dome is covered by the tunica
• corpus (body) is area of cells below the tunica that occupies central position in the meristem)

Question 9

Describe how the corpus and tunica in the shoot apical meristem divide differently to each other.

Answer 9

Cells in the tunica divide much more regularly than cells in the corpus.

Question 10

What do vascular bundles consist of?

What does the vascular ring divide into?

Answer 10

Consist of xylem and phloem tissues surrounded by fibres.

The vascular ring divides into an outer cortex and inner pith.

Question 11

What cells and tissues are referred to as primary growth?

Answer 11

Cells and tissues produced by the apical meristem are referred to as primary growth.

Question 12

Compare the stems of eudicotyledons with the stems of monocotyledons.

Answer 12

Stems of eudicotyledons have a ring of vascular bundles, dividing the stem into cortex and pith.

Stems of monocotyledons have vascular bundles scattered in ground tissue.

Question 13

What type of cells does secondary growth involve?

Answer 13

It involves cells from cambium, a secondary meristem.

Question 14

Describe the function of vascular cambium.

Answer 14

• produces wood
• adds width to stem
• produces xylem inside and phloem outside

Question 15

Compare the growth of cambium to the growth of the apical meristem.

Answer 15

Cambium produces sheets of new cells laterally, adding girth (radial growth). In contrast, apical meristem produces new cells behind it and continually adds length to a shoot (axial growth).

Question 16

Compare the cell organisation of primary growth tissues vs secondary growth tissues.

Answer 16

Cells in primary tissues are irregularly organised, whereas cells formed by secondary meristems show, at least initially, regular radial alignment.

Question 17

What does rhythmic growth result in?

Answer 17

It results in recognisable increments of secondary xylem, producing growth rings.

Question 18

What is the function of growth rings?

Answer 18

It can be used to age trees, but only in environments where rhythmic growth corresponds to the annual seasons.

Question 19

What is the only tissue permanently retained by the plant?

Answer 19

Wood.

Question 20

What is heartwood and sapwood?

Answer 20

Heartwood is xylem that has lost its water conducting capacity.
Sapwood is outer sheath of xylem that continues to function.

Question 21

What is cork cambium?

Answer 21

Another secondary meristem develops around the periphery of the stem and produces cork, which replaces the epidermis.

Question 22

What does cork cambium consist of?

Answer 22

Consists of numerous localised but overlapping short-lived meristems.

Question 23

Why are the meristems of cork cambium short lived?

Answer 23

As new meristems produce cork, older tissues on the outside are shed from the plant as bark.

Question 24

Why do large quantities of secondary phloem never accumulate in the stem?

Answer 24

Because older phloem is continually shed by the action of the cork cambium.

Question 25

What is periderm?

Answer 25

A protective tissue that replaces the epidermis in older stems and forms corky tissue.

Question 26

Where is bark produced? Where is wood produced?

Answer 26

Bark is produced outside the vascular cambium

Wood is produced inside the vascular cambium.

Question 27

What do monocots lack?

Answer 27

They lack secondary meristems but some still manage to form substantial trees.

Question 28

How are monocots still able to form substantial trees?

Answer 28

Via prop roots.

Question 29

What is an example of deadly secondary growth?

Answer 29

• strangler fig
• rapidly secondary growth of fig cuts off secondary growth in the host (fig covers and “strangles” host plant) and host plant eventually dies
• if attacked by strangler, you’d be better off being a palm (monocot) which does not have secondary growth