Plant Root

Question 1

Main Functions of Roots

Answer 1

1. Anchoring the plant firmly to a substrate (soil)
2. Absorption of water and minerals
3. Production of hormones.
   • shoot growth and development depend on the hormones

Question 2

Hormones

Answer 2

cytokinin and gibberellin

Question 3

Additional Functions

Answer 3

• Carbohydrate storage

• Protection

• Vegetative reproduction

• Parasitic roots

Question 4

Three types of root system:

Answer 4

1. TapRoot
2. FibrousRoot
3. Adventitious

Question 5

• single prominent root (tap root) that is much larger than all the rest and numerous small roots (lateral roots or branch roots) coming out of it

• Derived from the radicle (embryonic root)

• Anchorage

• Common in dicot and gymnosperm

• perennial and woody plants: roots undergo secondary growth

Answer 5

Tap Root

Question 6

(Taproot)
Nicotiana tabacum

Answer 6

Tobacco

Question 7

(Taproot)
Raphanus sativus

Answer 7

Radish

Question 8

(Taproot)
carrots, beets, radish, turnips

Answer 8

Fleshy taproot

Question 9

(taproot)
sweet potatoes, cassava

Answer 9

Swollen lateral roots

Question 10

taproot is about the carrot same size as the laterals

Answer 10

Sunflower

Question 11

• mass of many similarly sized, delicate and hair-like roots

• no prominent enlarged primary root

• Produced after death of radicle

• Derived from the root primordia found at the end of radicle

• Common in monocots and some dicots

• Absorption

Answer 11

Fibrous Root

Question 12

• Do not arise from pre-existing root
• Present in monocot and dicot

Answer 12

Adventitious Root

Question 13

arise from main trunk stem

Answer 13

brace root

Question 14

arise from the lateral branches of the main stem.

Answer 14

prop root

Question 15

• Secondary growth = ↑ quantity of healthy, functional wood (xylem) in the roots = ↑ no. of leaves and fine absorptive roots

Answer 15

Dicot Roots

Question 16

• No secondary growth = stem of an older plant is not wider than young plant, no ↑ conducting capacity, no more leaves or roots than young plant

• Stolons or rhizomes = ↑ size

• horizontal shoots branch and then produce adventitious roots

Answer 16

Monocot Roots

Question 17

the growing portion protected by root cap; push through the soil

Answer 17

Root tip

Question 18

Thick layer of cells that protects root apical meristem (root tip); constantly being worn away and renewed

Answer 18

Root cap

Question 19

complex polysaccharide secreted by dictyosomes of root cap for lubrication

Answer 19

Mucigel (Slime)

Question 20

• found behind the root cap
and root apical meristem
• few mm long
• where cells undergo division
and expansion

Answer 20

Zone of elongation

Question 21

• single celled extension of
epidermal cells which
increase absorptive area
• no line of demarcation in the
epidermal cells
• transitory(diewithin4-5
days)
• form only in a part of the
root that is not elongating

Answer 21

Root hairs

Question 22

• Cells are meristematic (cell division with transverse walls & forming files of cells that are pushed forward)

• As cells are pushed forward, they develop dense starch grains and their endoplasmic reticulum becomes displaced to the forward end of the cell = detects gravity because the starch grains settle to the lower side of the cell

Answer 22

Root Cap

Question 23

• more orderly than the shoot because it experiences no disruptions

Answer 23

Root Apical Meristem

Question 24

mitotically inactive central region

• cells are more resistant to various types of harmful agents such as radiation and toxic chemicals

• Serves as reserve of healthy cells

Answer 24

Quiescent center

Question 25

• Becomes active when root apical meristem or root cap is damaged and forms new apical meristem • Once the new meristem is established, its central cells become inactive, forming a

Answer 25

Quiescent Center

Question 26

• the region where the cells expand greatly; some meristematic, but mostly enlarging

Answer 26

Zone of Elongation

Question 27

outermost; forms epidermis (dermal region)

Answer 27

Protoderm

Question 28

at center; forms primary xylem/ phloem then metaxylem/ metaphloem (Stele/ vascular region)

Answer 28

Provascular tissue

Question 29

between protoderm and provascular tissue; Parenchyma cells that form root cortex

Answer 29

ground tissue

Question 30

• Root hairs grow outward • zone of elongation merges gradually with the

Answer 30

Zone of Maturation

Question 31

-transfer of minerals from the epidermis to the vascular tissue

Answer 31

Cortex

Question 32

diffusion through the walls and intercellular spaces

Answer 32

apoplastic transport

Question 33

absorption into the cytoplasm of a cortical cell and then transfer from cell to cell through plasmodesmata • Minerals do not have free access to the vascular tissues because the innermost layer of cortical cells differentiates into a cylinder called the endodermis

Answer 33

symplastic transport

Question 34

• Controls the passage of minerals across the vascular tissues • Consist of thick-walled cells (encrusted with suberin and lignin); diffusion is inhibited

Answer 34

Endodermis

Question 35

• bands of lignin and suberin on the radial walls (top, bottom and side walls) causing the cell walls to be water proof • Impermeable • minerals can cross the endodermis only if the endodermal protoplasts absorb them, then secrete them into the vascular tissues

Answer 35

Casparian strip

Question 36

Internal anatomy of young dicot root shows three general sections:

Answer 36

Dermal region Cortex Stele or vascular cylinder

Question 37

epidermis with root hairs

Answer 37

Dermal region

Question 38

outer collenchyma middle parenchyma inner endodermis

Answer 38

Cortex

Question 39

xylem forms a solid mass in the center, surrounded by strands of phloem; no pith (Vascular)

Answer 39

Dicot

Question 40

strands of xylem and phloem are distributed in ground tissue (Vascular)

Answer 40

Monocot

Question 41

inner wide cells

Answer 41

Metaxylem

Question 42

outer narrow cells

Answer 42

protoxylem

Question 43

Dicot: (Xylem) Two to four or more groups of protoxylem may be present (larger roots = ↑ no.)

Answer 43

Triarch Tetrarch Pentarch

Question 44

In monocot: (xylem) many xylem poles

Answer 44

Polyarch

Question 45

In monocot: (xylem) strands of xylem and phloem surrounding a parenchymatous pith

Answer 45

Siphonostele

Question 46

Vascular Tissue – most dicots (Phloem) found on the outer side

Answer 46

Protophloem

Question 47

Vascular Tissue – most dicots (Phloem) found on the inner side

Answer 47

Metaphloem

Question 48

• Found between the vascular tissue and the endodermis • parenchyma cells that constitute an irregular region • Where growth of lateral roots are initiated

Answer 48

Pericycle

Question 49

• Initiated by cell divisions in the pericycle • Localized cells remains mitotically active creating a small root primordium that become a root apical meristem and pushes outward • As it pushes outward, the new lateral root destroys the cells of the cortex and epidermis that lie in its path, ultimately breaking the endodermis. • Then, formation of a root cap, first protoxylem and protophloem elements connected to the vascular tissues of the parent root.

Answer 49

Origin Development of Lateral Roots

Question 50

Old dicot root shows two distinct regions:

Answer 50

1. Regionofsecondaryvascular tissues which include the 2. Region of periderm layers

Question 51

• provide long-term storage for carbohydrates that accumulate during summer photosynthesis

Answer 51

Storage Roots (Specialized roots)

Question 52

carrots, ube, radish, turnips

Answer 52

fleshy taproots

Question 53

• Adventitious roots from stems • Pandanus (screwpine), Ficus (Banyan trees)

Answer 53

Prop roots (specialized roots)

Question 54

Pandanus

Answer 54

screwpine

Question 55

Ficus

Answer 55

Banyan trees

Question 56

in corn plant – for additional support and absorption

Answer 56

Brace roots (specialized root)

Question 57

Velamen in aerial roots of orchids

Answer 57

Water retention

Question 58

dead cells, white; acts as waterproof barrier

Answer 58

Velamen

Question 59

Chlorophyllous roots

Answer 59

Photosynthesis

Question 60

Contractile roots of bulbs like onions, gladiolus, garlic

Answer 60

Movement

Question 61

due to change in shape of cortical cells

Answer 61

Contraction

Question 62

for absorption

Answer 62

Parasitic (haustorial roots)

Question 63

diffuse root system i.e Tristerix

Answer 63

Haustorium

Question 64

tall, plate-like, expanded roots for great support

Answer 64

Buttresses

Question 65

breathing roots of mangrove for aeration

Answer 65

Pneumatophores

Question 66

nitrogen fixation, formed by mitosis of cortical cells

Answer 66

Root nodules

Question 67

bacteria, fill host cells with bacteroids w/c convert N2 to nitrogenous compds

Answer 67

Rhizobium

Question 68

Other types and root modifications

Answer 68

Protection Spiny roots of tugue

Question 69

• Birds deposit seeds on the branch of a host tree • When the seed germinates, the roots cling to the bark of the host tree, grow, hugging the host tree until it reach the soil.

Answer 69

Strangler Figs

Question 70

association between a soil fungus (fungal hyphae) and roots

Answer 70

Mycorrhizae

Question 71

hyphae penetrate between the outermost root cortex cells but never invade the cells

Answer 71

ectomycorrhizal relationship

Question 72

hyphae penetrate the root cortex as far as the endodermis; but cannot pass the Casparian strip

Answer 72

endomycorrhizal

Question 73

small structure formed by fungi; filled with P

Answer 73

Arbuscule

Question 74

Fleshy taproots (i.e. carrots, beets, radishes)

Answer 74

Carbohydrate storage

Question 75

in Crysophila and Mauritia, roots grow out of the trunk and harden into sharp spines

Answer 75

protection

Question 76

roots spread horizontally and produce shoot buds (i.e. willows, sorrel)

Answer 76

Vegetative reproduction

Question 77

modified roots attack other plants and draw water and nutrients out of them (i.e. mistletoe, dodder)

Answer 77

Parasitic roots