lecture 14, Roots

Question 1

what is pando?

Answer 1

the heaviest and oldest living organism on earth, known as the trembling giant and contains a massive underground root system

Question 2

where did roots evolve from?

Answer 2

subterranean portion of ancient vascular plants. evolved from rhizoids which are protuberances that extend from the lower epidermal cells of bryophytes and algae

Question 3

what is stele?

Answer 3

primary tissues in a vascular plant. vasculature developed from solid cylinder in protostele

Question 4

what is the siphonostele?

Answer 4

central pith surrounded by vascular tissue

Question 5

over evolutionary time, what did the protostele evolve into

Answer 5

siphonostele and then the eustele

Question 6

what does the stele contain?

Answer 6

pith, leaf gap, and phloem

the pith evolves in the middle of the stele, so no vasculature surrounds this ground tissue. the leaf gap is where vascular tissue goes off to leaves; gap is where parenchymal cells of leaf develop. the phloem is on the outside always

Question 7

how did microphylls evolve?

Answer 7

evolved as outgrowths, enations
-single strand of vasculature
-protosteles
-no leaf gap

Question 8

how did megaphylls evolve?

Answer 8

by fusion of branch systems
-siphonostele
-pith and leaf gap
-common to all vascular plants

Question 9

how did roots evolve?

Answer 9

as part of the apical-basal meristem; primary tissue extensions into the soil- not as lateral appendages like the leaves

Question 10

characteristics of a monocot:

Answer 10

-contain a single cotyledon
- long narrow leaf, parallel veins
-vascular bundles scattered
-floral parts in multiples of 3

Question 11

characteristics of a dicot:

Answer 11

• two cotyledon
• broad leaf, network of veins
  -vascular bundles in a ring
  -floral parts in multiples of 4 or 5

Question 12

what is the dicot root structure?

Answer 12

vascular bundle is in the center, xylem matures from proto to meta, phloem is on the outside, surrounded by pericycle

Question 13

primary growth in dicot roots comes from and gives rise to …

Answer 13

comes from the procambium, which give rise to:
1. vascular tissues, phloem and xylem
2. non-vascular, pericycle, one/more layers that surrounds the bundle

Question 14

what is secondary growth composed of in dicot roots?

Answer 14

vascular cambium –> secondary vascular tissue
cork cambium –> periderm- cork tissue

Question 15

what happens during secondary growth?

Answer 15

1. growth of secondary xylem and phloem crushes primary phloem forming fibers
2. secondary phloem and xylem form rings separated by the vascular cambium
3. periderm in most woody roots provides protective layer - replacing epidermis

Question 16

what happens after 1 year of secondary growth?

Answer 16

• epidermis sloughing off
• periderm developing
• primary phloem crushed into fibers
• secondary vasculature growing

Question 17

what is the monocot root structure

Answer 17

xylem and phloem both in ring shape, xylem is in the inner ring and phloem the outer.
contains a center of vasculature that has parenchymal cells (pith)

Question 18

primary and secondary single layer in a root?

Answer 18

primary: epidermis
secondary: periderm

Question 19

what are the specialized structures in the roots:

Answer 19

root cap, mucigel sheath, root hairs

Question 20

what is the specialized dermal root structures?

Answer 20

1. root cap:
   - detection of gravity
   - lubricates passage of cells through soil
   - secretes mucilage
2. mucigel sheath:
   - mucilage secretion
3. Root hairs:
   - single cell wide
   - water acquisition

Question 21

what are the components of root ground tissues?

Answer 21

cortex, endodermis, casparian strip

Question 22

what does the casparian strip contain?

Answer 22

suberin, lignin, and a waterproof layer that protects interior

Question 23

how does lateral root development occur?

Answer 23

arises from pericycle, occurs some distance behind region of elongation, new lateral root primordium pushes through the cortex

Question 24

what are the main functions of the root

Answer 24

• absorption and conductance
• anchoring
• storage
• symbiosis

Question 25

what is the first root known as?

Answer 25

the primary root

Question 26

what are subsequent roots that emerge from primary roots known as?

Answer 26

lateral roots

Question 27

root emerging from the stem is known as….

Answer 27

adventitious roots

Question 28

what are the different combinations of primary, lateral, and adventitious roots

Answer 28

taproot, fibrous root, prop roots, stilt roots, pnematophores

Question 29

characteristics of taproot system

Answer 29

largest root, central to the rest of the root system; lateral roots arise from main root.
in all vascular plants except monocots

Question 30

characteristics of fibrous root system

Answer 30

-primary root emerges from the seed, but is short-lived
-adventitious roots arise from the stem and give rise to lateral roots
-lateral roots develop into small and dense systems
-typical of monocots

Question 31

characteristics of aerial roots:

Answer 31

• stilt and prop roots
• mainly adventitious
• specialized in providing additional structural support for the plant

Question 32

characteristics of pneumatophores:

Answer 32

• commonly found in mangrove species
• grow in saline mud flats
• lateral roots that grow upward
• oxygen intake

Question 33

what are the different forms of uptake of water and minerals?

Answer 33

• apoplastic: outside the plasma membrane of cell - material diffuse freely; between cell walls of adjacent cells
• symplastic: along the inner side of the plasma membrane; often via plasmodesmata

-transcellular: primary/secondary active transport of solutes across cells

Question 34

how are minerals freed from the soil?

Answer 34

by pumping protons - reason why soil pH impact plant nutrition