Lecture 6

Question 1

Functions of Roots

Answer 1

•Water uptake
•Nutrient capture
•Anchorage into soil
•Roots hold soil together
•Root nodules can fix nitrogen into soils
•The rhizosphere

Question 2

Where do the best fodsilized roots comes from

Answer 2

Rhynie Chert a 407 million year old site in Scotland

Question 3

Where did roots evolve from

Answer 3

Sporophytes
In Devonian period c. 410 million years ago

Question 4

The evolution of roots emerged as a consequence of what

Answer 4

the differentiation of underground stems (rhizomes) into two specialized organs:

Question 5

Describe the am two specialised organs formed from differentiation of underground stems (rhizomes)

Answer 5

(i)thicker perennial stems that form conduits to distribute water and nutrients, serve as stores and support above-ground structures; and
(ii) thinner, longer structures to absorb water and nutrients.

Question 6

Where did root hairs possibly evolve from

Answer 6

Rhizoids of earlier plants to increase the volume of substrate available for exploitation

Question 7

Subsequent evolution of roots has yielded much- branched axes down to how many μM

Answer 7

40 μM

Question 8

What is the limit of 40 μM in branched axes of roots set by

Answer 8

Long distance transport constraints

Question 9

The association of roots with fungi from the start enabled what

Answer 9

better uptake of nutrients from a larger volume of substrate

Question 10

What does chemical weathering consume

Answer 10

CO2

Question 11

Roots with fully integrated vascular systems were essential to evolution of large plants and tall tree trunks for what

Answer 11

Water transport
Bio mechanical strength

Question 12

Example of positive feedback

Answer 12

Bigger plants need deeper soils
Plants contribute to the formation of souls by decomposition leading to deeper soils

Question 13

When a seed germinates what is the first structure to appear

Answer 13

The root / radicle

Question 14

Other roots that branch out from the primary root are called what

Answer 14

Secondary roots

Question 15

What are the stages of seed germination

Answer 15

1. Imbibition: Seeds absorb moisture and swell until the seed coat bursts
2. The radicle pushes through the seed coat downwards into the soil
3. Primary roots begin to develop and the hypocotyl forms a hook that straightens out, pulling the cotyledons above ground
4. The primary leaves begin unfolding and the stem elongates.
5. The true leaves completely emerge and the cotyledons
   eventually fall off.

Question 16

What is Imbibition

Answer 16

Seeds absorb moisture and swell until the seed coat bursts

Question 17

Write a short note on Monocots

Answer 17

a flowering plant with an embryo that bears a single cotyledon (seed leaf). Monocotyledons constitute the smaller of the two great divisions of flowering plants, and typically have elongated stalkless leaves with parallel veins (e.g. grasses, lilies, palms,orchids).

Question 18

Write a short note on Dicots

Answer 18

a flowering plant with an embryo that bears two cotyledons (seed leaves). Dicotyledons constitute the larger of the two great divisions of flowering plants, and typically have broad stalked leaves with net-like veins (e.g. daisies,bean,spinach ,rosehawthorns, oaks).

Question 19

What increases the surface area of the root

Answer 19

Tiny root hairs

Question 20

root cap lines from what cell

Answer 20

Apical cells to tissues in more mature parts of the roots

Question 21

What is a protostele

Answer 21

Solid cylinder of xylem

Question 22

Example of storage roots

Answer 22

carrot (Daucus carota),
sugar beet (Beta vulgaris),
sweet potato (Ipomoea batatas)
yams (Dioscorea spp.)

Question 23

What are storage roots

Answer 23

Roots adapted to store products photosynthesised in the shoot
Products are synthesised above ground and transported to root in phloem where they reside until needed to complete life cycle

Question 24

Example of Air roots

Answer 24

Mangroves
Cypress Knees

Question 25

What are air roots also known as

Answer 25

Pneumarophores

Question 26

What are air roots

Answer 26

In some trees that live in swamps

grow above the surface of the water and allow oxygen to be transported to the inner cortex of the root system, and CO2 to escape from the root interior.

Question 27

Name the primary structure in Air roots/ Pneumatophores that allow gas exchange

Answer 27

Lenticels

Question 28

What are Buttress roots

Answer 28

vertically flattened roots that project out of the ground and lower trunk at the base of large trees.

Question 29

What are Prop/Stilt roots

Answer 29

adventitious roots that develop on a trunk or lower branch that begin as aerial roots but eventually grow into a substrate of some type;

Question 30

Function of Prop/Stilt roots

Answer 30

Provide mechanical support having good compression or tensile properties to help support trees at their bases

Question 31

What are Adventitious roots

Answer 31

roots that arise from anything other than the radicle

Question 32

What do Tap root and Fibrous roots systems arise from

Answer 32

The Radicle