Root adaptations

Question 1

What is an adventitious root?

Answer 1

Any root that does not originate from the radicle, or primary root system, can be considered to be an adventitious root.

These offer the plant the ability to produce roots from areas other than the seed.

Examples include the rooting of cuttings, or the support of colonisation (spread) of, for example Rubus fruticosus which spread with arching stems that produce roots where they touch the ground.

Question 2

What is a pneumatophore root?

Answer 2

Roots that exist within wet soils, that make use of aerenchyma cells to allow for the diffusion of oxygen.

Pneumatophores sometimes float to the water surface, and have openings for gaseous
exchange, or rise out of the water, as is the case with Mangrove swamps.

Plant examples include Taxodium distichum (Please note some sources are
questioning whether this plant has true pneumatophores, however a
conclusive decision has yet to be made and so these plants can be considered
to have pneumatophores.)

Question 3

What is advantageous about a fibrous root?

Answer 3

offering the plant the ability to absorb water and minerals over a large surface area
close to the surface of the soil, thus making use of low levels of rainfall or irrigation.

Fibrous roots can also help to reduce soil erosion preserving the root environment.

Plant examples include: any named monocotyledonous or Stipa gigantea

Question 4

Impact of oxygen levels in soil on roots

Answer 4

The impact of reduced oxygen levels on rooting depth. This can result in raised roots in some tree species. Some roots of these species are adapted to maximise the availability of oxygen and can therefore grow close to the surface of the soil.

Plant examples include: Sorbus aria or Prunus ‘Kanzan’

Question 5

What are some of the impacts of plant selection in hard landscaping or grass areas?

Answer 5

Raised roots can lift paving, and result in blade strike within grassed areas.

Plant examples include: Sorbus aria or Prunus ‘Kanzan’.

Question 6

What effect does root adaptations have on weeds?

Answer 6

Some plant species are able to produce new plants (due to totipotency) from
fragments of root, examples include Taraxacum officinale, and Circaea
lutetiana

Question 7

How do root adaptations affect transplanting?

Answer 7

The ability of plant roots to regenerate is used within horticulture with the root pruning of plants during the transplanting process.

This can include Allium porrum or the pruning of many deciduous bare root shrubs or trees
when planting, e.g. Prunus padus.

Question 8

What is colonisation?

Answer 8

Stolons or suckering from roots Examples could include Rubus fruticosus
suckering from roots, for example Rhus typhina.

Question 9

the concept of totipotency as it applies to propagation involving roots

Question 10

What role do roots play in the life of a plant?

Answer 10

Roots help to anchor the plant in the ground.
* They absorb water and nutrients
* They actively seek out water and nutrients, this is called foraging behaviour.
* Roots will sometimes store nutrients as carbohydrates.
* In some cases, they will store water as well.
Sometimes roots absorb nutrients from other roots thru parasitic species
Roots link with mycorrhizal fungi to find more water/nutrients

Question 11

Why do roots breathe?

Answer 11

Roots need to be able to breathe in order to respire to carry out their functions
of absorbing water and nutrients.

Question 12

What is foraging behaviour of a root?

Answer 12

This is the ability of roots to go towards good sources of water and nutrients, which in
competitive environments (or environments with limited resources) is a very useful ability.

Question 13

What is a tropism?

Answer 13

The growth movement in a specific direction.

a response by a plant organ to an environmental stimulus which results in
movement or growth.

Roots forage for water and nutrients through
tropic mechanisms

Question 14

What is gravitropism or positive geotropism?

Answer 14

Seed tropism:
Downward growth - as in the radicle of the seed growing downward and embryonic shoot growing upwards.

Question 15

What is a taproot? What are the advantages to a plant in maintaining a taproot throughout its life? Name ONE additional adaptation to its taproot that some plants have.

Answer 15

A taproot is a root that plunges straight down from the above ground part of the plant and which merges with the stem. It is derived directly from the radicle - the embryonic root which emerges from the seed – but in
dicotyledons only.

Many plants keep their tap root, as it helps anchor the plant and in some species it acts as a nutrient store – for e.g. in carrots and parsnips the tap root swells to store nutrients to enable rapid growth in the spring.

Question 16

In what circumstances do adventitious roots enable a plant to spread?

Answer 16

When they emerge from a rhizome which is travelling horizontally, and branching. They will secure the plant in position and enable resources for shoot growth in new territory.

Also in certain species, such as willows (Salix
spp.) branches or twigs on damp ground will produce adventitious roots, effectively layering the plant.

Question 17

What is a stilt root?

Answer 17

Stilt roots help support tall stems. They emerge from the stem just above the soil.
Example: Zea officinarum

Question 18

What is a prop root?

Answer 18

Roots that project down from branches and function as trunks. THey do develop roots.

Fiscus elastica (rubber plant)
Ficus benghalensis (Banyan tree)

Question 19

What is an aerial root?

Answer 19

Adventitious roots that emerge from the stem nearby a moist surface. The roots penetrate a tiny distance to hold on.

Hedera helix

Aerial roots can absorb water from rain and gather nutrients from dead leaves. They never need to touch the ground.

Example: Epiphytic plants: orchids and bromeliaceae

NOTE: Some tropical plants have aerial roots that merge into prop roots to support climbing.

Example: Monstera deliciosa

Question 20

What is Pneumatophore

Answer 20

a projection of a root which emerges above ground to form structures which are nicknamed Knees.

grow from horizontal roots just below the surface and protrude upward from the ground or water it’s thought that the pneumatophores function to transport air to drowned roots underground

Taxodium distichum (Bald cypress that likes swampy conditions)

Question 21

What is totipotency of roots?

Answer 21

Roots produce shoots which grow into new plants. Initially attached to parent but eventually independent clone. Usually through adventitious buds from roots (suckers).

Cornus alba (pretty but can be problematic)

Question 22

What often stimulates the production of suckers?

Answer 22

Damage to the root: mowing lawn. EX: Rhus typhina.

Question 23

What are some good and bad points about adventitious roots?

Answer 23

Cut roots can continue to grow: Acanthus mollis

However good potential for root cutting propagation: Example: Phlox paniculata or Papaver orientale.

Question 24

In planting, what is important to know about roots?

Answer 24

1. Do they have enough room to grow without damage to property?
   Ex: Salix spp (WIllow) and Populus spp. (Poplar) can both damage foundation.
2. Always better to plant young plants so they have time to grow and adapt to the soil. Older plants will never adapt fully.
3. Younger plants will catch up to the older plants within a year or so… CHEAPER and MORE SUSTAINABLE (transport and carbon footprint)

Question 25

Issue of adventitious roots of weeds?

Answer 25

Spread through rhizomes and will continue to grow via rhizomes.

Example: Bindweed (Calystegia sepium)
Most likely will need translocated weed killer to get rid of it.

Question 26

Grafted trees growth?

Answer 26

Growing a dwarf tree means putting a full tree stem on dwarf root stock to prevent full growth. As it’s a smaller dwarf stem, the tree may need continuous staking as the dwarf roots are not strong enough.

Question 27

Monocot roots and transplanting?

Answer 27

Easy to transplant as root is superficial as they are produced from base of the roots. Eudicots cannot do this.

Question 28

Name some of the ways in which the damage to plant
root systems during transplantation can be minimised.
Consider this from the perspective of the ‘whole plant life story’, starting in the nursery, going through the planning of planting, planting itself, and post-planting.

Answer 28

MODEL:
1) In the nursery: Trees and shrubs can be prepared for transplanting by digging around the plants as they are growing in a nursery bed, severing longer roots and thus stimulating the development of a more confined, denser root system, which will be better able to adapt to a new planting situation.
2) Planning: planting to take place in the autumn or early winter, to give transplants maximum time in cool moist soil to begin growing new roots.
3) Planting: to take place in overcast weather, with bare roots being exposed to the air for as short a period as possible; plants awaiting planting to have roots covered with plastic sheeting. Dipping in water before hand. If soil is not moist, watering in immediately after planting, which will help settle soil around
roots. Soil to be firmed around base of plant.
4) Aftercare: new plants to be watered on an ‘as needed’ basis during the following year, i.e. during periods of hot weather or extended drought.

Question 29

Imagine that you are managing a public park, where
there are paths, areas of mown grass, some buildings, and trees. What are some of the issues you may expect to find regarding plant roots? How might these be managed, in order to minimise damage to both trees and park features?

Answer 29

Older tree roots may be lifting areas of paving – so paving or hard surfaces may need to be re-set, at a higher level, or even diverted away from tree roots.

Poor grass growth visible around some trees – consider removal and replacement with shade tolerant groundcover plants or areas of mulch.

Assess trees near to buildings or other structures – are they likely to become a problem in future years? either through root damage to foundations or from
branch drop. Consider calling in professional advice.

Are there areas where compaction caused by foot traffic may be affecting tree roots? Consider re-directing paths, low-level fencing to keep people
away or closing off ‘desire paths’. Then consider how soil might be broken up.

Ground cover planting may help too – discouraging foot traffic and opening up soil.

Question 30

What is a taproot? What are the advantages to a plant in maintaining a taproot throughout its life? Name ONE additional adaptation to its taproot that some plants have.

Answer 30

MODEL:
A taproot is a root that plunges straight down from the above ground part of the plant and which merges with the stem. It is derived directly from the radicle - the embryonic root which emerges from the seed – but in
dicotyledons only. Many plants keep their tap root, as it helps anchor the plant and in some species it acts as a nutrient store – for e.g. in carrots and parsnips
the tap root swells to store nutrients to enable rapid growth in the spring.

Question 31

In what circumstances do adventitious roots enable a
plant to spread?

Answer 31

MODEL:
When they emerge from a rhizome which is travelling horizontally, and branching. They will secure the plant in position and enable resources for shoot growth in new territory. Also in certain species, such as willows (Salix spp.) branches or twigs on damp ground will produce adventitious roots, effectively layering the plant.

Question 32

Why do roots need to breathe?

Answer 32

MODEL:
Roots respire actively, as they need to power processes that actively absorb certain nutrients from the soil to get them into the xylem for distribution to the rest of the plant. Respiration needs oxygen, which can only be obtained from air in the soil.

Question 33

What happens if plant roots become waterlogged for
any period of time?

Answer 33

MODEL:
Waterlogging prevents roots breathing (absorbing oxygen), this can cause the death of the root, there is then the possibility of fungal infection, which
can cause further damage. As the root system progressively dies, the rest of the plant will suffer from water and nutrient loss.

Question 34

Explain why a potato can be used for propagation but
not a single dahlia tuber, using the concept of totipotency.

Answer 34

MODEL:
Tubers vary in their level of totipotency, i.e. the ability to produce new shoots and roots. Some plant tubers are simply storage vessels for carbohydrates,
e.g. dahlias, in this case attached to growth point. In others, there are small growth points (areas of meristem) on the surface of the tuber, as in potatoes;
this enables the potato tuber to produce new (clonal) plants.

Question 35

What adaptation provides oxygen to roots

Answer 35

Pneumatophore.

Swamp plant like Taxodium distichum provides oxygen to roots in swamps.

Question 36

What is a good sign of totipotency?

Answer 36

Adventitious roots are a sign of totipotency - the ability to produce new growth that can
potentially result in a new plant.

Question 37

Example of some plants that can grow buds on their roots to form new plants?

Answer 37

Phlox can be propagated by root cuttings GOOD or
a bad thing the spread of weeds like ground elder, Aegopodium podagraria).

Question 38

Can you propagate through roots?

Answer 38

Root cuttings are a specialised technique where we cut short sections of thicker roots and lay them out in trays of substrate or compost as a way of propagating the plant.

This is useful for Phlox, Japanese anemones, and a few other plants.

Question 39

Why do plants need nitrogen

Answer 39

Plants need nitrogen to build amino acids, to build proteins, to build growth. Nitrogen is a
key plant nutrient.

Question 40

Explain root nodules

Answer 40

Bacteria in nodules fix nitrogen to produce soluble N containing nutrients.

A symbiotic relationship similar to root mycorrhizae

The ability of members of the pea family (legumes or leguminous plants) to put nitrogen into the soil has been a very useful one.

Plants that fix N: Legumes (Fabaceae); Alders (Alnus spp) and Casuarina spp.

Question 41

Problematic roots: Foundations

Answer 41

It is generally only an issue where you have plants with very strong root systems: trees such as poplars and willows. It is also generally only a problem on clay soils, which as they dry out, shrink and can weaken and allow building subsidence.

Question 42

Problematic: Paving

Answer 42

Contemporary landscape tree planting techniques aim to minimise this, for example, by having a zone around the tree with a different kind of material that reacts better to the pressure from roots.

Paving can reduce the ability of the roots to breathe which is very important for roots.

Modern solutions for this are materials that are permeable and allow a certain amount of
water and gaseous exchange between the atmosphere through the material and down to the soil underneath.
Correct tree planting methods will not only ensure protection of the hard surfaces, but also ensure tree health.

Question 43

Trees grown in Grass

Answer 43

Minimize grass
Replace with groundcover
Reduces root damage
Reduces damaging foot traffic

Question 44

Transplanting trees checklist

Answer 44

Nursery to encourage healthy root growth
Plant during dormant season
Care based on particular needs of plant
Possibly purchase rootball or containerized

Question 45

Transplanting needs

Answer 45

Soil preparation:
Encourage root growth by breaking up the soil
Encourage foraging by NOT adding nutrients
Reduce possibility of fungal disease by NOT adding OM

Question 46

How does foraging help protect a plant

Answer 46

Compost NO as it tends to hold too much water
Growth of harmful fungi - NO compost
Localized root death with movement
ENCOURAGE PLANT TO FIND ITS OWN