Primary growth of Roots and Shoots

Question 1

What are the 3 stages of growth?

Answer 1

1. Mitosis
2. Cell Expansion
3. Cell differentiation and maturation

Question 2

What are apical meristems?

Answer 2

Zones of active division at tips of roots and shoots

Question 3

What does the apical meristem produce?

Answer 3

1. Protoderm: makes dermal tissue
2. Ground meristem: makes ground tissues
3. Procambium: makes vascular tissues

Question 4

What are plant meristems?

Answer 4

zones of undifferentiated, perpetually juvenile (immature) cells capable of mitosis

Question 5

What are the root functions in root primary growth?

Answer 5

Penetrate soil 
Take up nutrients and water 
Exclude undesirable materials 
Transport water and nutrients 
Transport photosynthate from shoot to root 
Anchor and support the shoot

Question 6

True or false: Roots can grow up to 25mm a day or 1 meter in 40 days

Answer 6

True!

Question 7

True or false: Root depth can exceed tree height especially in arid environments

Answer 7

True!

Question 8

True or false: Conifers do not have a taproot system

Answer 8

False! They do!

Question 9

True or false: Monocots have a fibrous root system

Answer 9

True!

Question 10

How do roots develop?

Answer 10

1. First root from the embryo (the radicle) becomes primary root
   and develops into tap root in gymnosperms and eudicots
2. Root apical meristem (under root cap) produces cells in all direction
3. Behind apical meristem is the one of elongation. Then zone of differentiation and maturation
4. Apical meristem produces protoderm to outside, procambium in center and ground meristem between
5. Protoderm produces epidermis
6. Some cells expand laterally into root hairs for water and nutrient uptake

Question 11

What is the xylem?

Answer 11

the center of the root

Question 12

Where is the primary phloem found?

Answer 12

In patches

Question 13

What does the endodermis do?

Answer 13

forms a tight and perfect ring, have a strip of wax called suberin as a barrier to control what stays in and out

Question 14

What does the ground meristem produce?

Answer 14

Cortex
Endodermis
Pericycle

Question 15

What does the cortex do?

Answer 15

for storage, also involved in lateral transport

Question 16

What does the endodermis do?

Answer 16

controls flow of materials into the center of the root (stele)
Radical cells walls are suberized forcing all substances to cross a membrane into the protoplasm, or be excluded

Question 17

What does the pericycle do?

Answer 17

like cortex but patches become meristematic and form new apical meristems for lateral roots

Question 18

What does the procambium produce?

Answer 18

Primary phloem
Primary xylem
Vascular cambium

Question 19

What does the primary phloem do?

Answer 19

living cells for transport of food, hormones,

Question 20

What does the primary xylem do?

Answer 20

dead, hollow cells for upward transport of water, mineral nutrients, etc.

Question 21

What does the vascular cambium do?

Answer 21

A secondary meristem

Question 22

What does it mean to be negatively gravitropic?

Answer 22

The stems grow away from light

Question 23

What is the root cap filled with?

Answer 23

Amyloplast so they can fall

Question 24

What is the process of gravitropism?

Answer 24

Amyloplsts settle
Interaction with enodplasmic reticulum
Send hormonal signal from the root cap to the zone of elongation
Most cell expansion is in the zone of elongation
Primary roots are positively gravitropic
Primary laterals grow at around 45 degrees
Secondary laterals are indifferent
Mechanism: root cap cells contain amyloplasts that settle with gravity. Hormonal signals (ER Involved) sent to zone of elongation. Greater elongation on upper side causes curvature.

Question 25

What happens in primary shoot growth?

Answer 25

Shoot apical meristem is in shoot apex

Leaf primordia arises on sides

Question 26

What are nodes?

Answer 26

Point of leaf attachment

Question 27

What is the internode?

Answer 27

The shoot segment between 2 nodes

Question 28

Where do apical meristems form?

Answer 28

In leaf axils

Question 29

What is phytomere?

Answer 29

1 node + 1 internode + leaves at that node + axillary meristems

Question 30

What does the shoot apical meristem produce?

Answer 30

protoderm to outside and procambium in strands and ground meristem

Question 31

What does the protoderm produce?

Answer 31

Spidermis which has a wavy coating (cuticle) and lenticels for gas exchange

Question 32

What does ground meristem produce?

Answer 32

cortex and pith for storage

Question 33

What does the procambium produce?

Answer 33

vascular bundles of primary phloem, primary xylem and fascicular cambium