Topic 9.3: Growth in Plants

Question 1

What kind of growth do most plants have?

Answer 1

indeterminate growth

Question 2

What is indeterminate growth?

Answer 2

The ability to continuously grow (under the right conditions)

Question 3

Growth in plants is concentrated in …

Answer 3

the meristem at the tip of the roots and shoots.

Question 4

What is the meristem made up of?

Answer 4

undifferentiated cells (unspecialized cells)

Question 5

What is the apical meristem?

Answer 5

areas for growth on the roots and shoots of the plant.

Question 6

What does the apical meristem do in the roots?

Answer 6

elongates it and makes the roots grow deeper into the ground

Question 7

What protects the meristem in the roots?

Answer 7

the root cap

Question 8

What does the apical meristem do in the shoots?

Answer 8

increases the length of the stem to develop leaves and other above ground structures. (done through mitosis)

Question 9

In the axillary buds, apical meristems create…

Answer 9

dormant meristems (where the leaf joins the stem, that have the potential to grow into new shoots or branches)

Question 10

How do plants respond to changes in the external environment?

Answer 10

by changing the number of cells that the meristem produces

Question 11

Plant hormones are usually…

Answer 11

small organic molecules (simpler than animal hormones)

Question 12

What is auxin?

Answer 12

a plant hormone than is synthesized at the apical meristem and is transported down the stem.

Question 13

What do auxins do?

Answer 13

cell elongation and inhibits the growth of the axillary (side) buds, causing the plant to grow vertically (upwards)

Question 14

The further auxin travel from apical meristem, …

Answer 14

the lower it’s concentration becomes

Question 15

Auxin inhibits the growth of…

Answer 15

the axillary buds

Question 16

Define Apical dominance

Answer 16

when the shoot of the of the plant grows while also preventing the growth of the axillary buds.

Question 17

Define tropism

Answer 17

when the plant grows in a particular direction because of the external stimulus (ex: light, gravity, ect.) (plant shoots respond to their environment through tropisms.)

Question 18

Define phototropism

Answer 18

the response of the plant to light

Question 19

Define geotropism

Answer 19

the response of the plant to gravity

Question 20

Shoots usually show —– phototropism and —— gravitropism.

Answer 20

positive , negative

Question 21

Roots generally show ——phototropism and ——- gravitropism

Answer 21

negative, positive

Question 22

Why do roots and stems grow unevenly?

Answer 22

because of the uneven distribution of auxin along the growing roots and stems, which makes cells grow unevenly, also causing them to bend in a particular direction.

Question 23

The concentration of auxin that elongates shoot cells by accumulating the the side of the stem, inhibiting the growth of the cells in the…

Answer 23

root

Question 24

How does auxin move from one cell to another?

Answer 24

1) Apical meristem has phtotoropins (detect light intensity)

2)If light is equally bright on all side of the shoot tip, auxin will move symmetrically down (via specialized protein pumps)
-Auxin influx carriers carriers in their apical (top) cell)
-Auxin efflux carriers in their bottom (basal) cell membranes.
3) There will be even cell growth and vertical extension of the stem.
——————————————-
if there is a difference in light intensity on different sides of the shoot…
-Phototropism will make some kinds of auxin efflux carriers to increase on the internal lateral (side) membrane.
-so auxin will be transported to the shaded side of the plant
-the shaded side will experience greater cell elongation
- stem will bend towards light

Question 25

What happens when auxin is accumulated on the shaded side?

Answer 25

1) Auxin will change gene expression of several genes.
- will trigger transcription of genes that make proton pumps.
2) Cell elongation in stem happens
-Protons will move out of cytoplasm and into the cell wall. (via proton pumps)
- so cell becomes more flexible (because there is less amount of bonds between cellulose microfibrils)