TAMU HORT 201 Exam 4

Chimera

a plant or plant part composed of genetically different layers

What is the most common example of a chimera plant?*

variegated plants

variegated plants*

where different regions or layers of the leaf are yellow or white due to no chlorophyll development

Example of variegation

Why can you not propagate a chimera through a cutting that needs to form shoots (leaf and root cuttings)?

because they will never come out looking like the original chimera

If you want to propagate a chimera plant, what type of cutting do you have to take?

Any cutting that only needs to form adventitious roots

If you have a variegated leaf cutting where the edges are mutated and do not have chlorophyll, and a shoot forms from the edge of that leaf, what will the shoot look like?

It will be fully mutated, and all of the leaf will be pale because it will have no chlorophyll

If you have a variegated leaf cutting where the edges are mutated and do not have chlorophyll, and a shoot forms from the center of that leaf, what will the shoot look like?

It will not have any mutation and will lack variegation in the rest of the plant

Grafting

combining diff parts of plants into 1

Scion

the upper part of the graft that becomes the shoot system of the new plant

Stock

the lower part of the graft that becomes the root system of the new plant

Budding

a type of graft where the scion is just a bud piece or small chip of wood with a bud attached

Why do we graft/bud plants?

1. used for plants that cannot be propagated by other means (Ex: plants in adult phase)
2. decrease time for flowering and fruiting
3. Obtain desirable characteristics of the rootstock like disease resistance, adaptation to climate, and dwarfing
4. change variety: make better fruit/flower
5. special forms (ex: tree roses)
6. Repair damage
7. virus indexing: test plants for virus

How do we use grafting to index viruses?

test plants for disease by grafting a part of a plant onto a plant that is known to be sensitive to a virus. If the plant that is sensitive begins showing signs of disease, we know the new plant is infected.

For a graft to be successful, the plants must be...

alike, you can only graft things of a similar species onto each other

For a graft to be successful, the scion and the stock must both possess what?

a cambium

For a graft to be successful, what part of the two plants must be firmly connected?

the cambium of the scion and stock

How do we ensure the cambia of a stock and scion match up?

make sure they are roughly the same size and we make specific cuts to make sure they line up.

What types of grafts are used to repair damage?

Inarching, Bridge graft, and Brace graft

Inarching graft diagram

Inarching grafting is used...

to replace damaged root system

Bridge graft diagram

Bridge grafting is used...

to repair damaged trunk

Brace graft diagram

Brace grafting is used...

to support weak branches

What kinds of grafting are used when the scion and stock are approximately the same size?

Whip/tongue graft, splice graft, and saddle graft

Whip or tongue graft

cut like splice but make an additional cut down middle before connecting both

What is the most common graft when the stock and scion are approximately the same size?

Whip or tongue graft

Why is the whip/tongue graft the most commonly used?

because if it's done right the graft will hold itself together

Splice graft

graft method of matching angle cuts to the scion and the stock

Saddle graft

horse shoe shape, or U shape graft through stem

Types of grafts used when scion is smaller than stock

Side graft, Cleft graft, wedge/notch/saw-ferf graft, Bark inlay graft, Approach graft, and Topworking

Side graft

cut into side of stock and shove smaller scion into cut

Cleft graft

Cut made into a large branch and a twig is inserted

Wedge/notch graft

make cuts on side edge of stock and insert scion into the cuts - like cleft but around the edges

Bark inlay graft

grafting the scion by pealing back the bark of the stock

When can we do a bark inlay graft?

when the bark is slipping

What does it mean when the bark of a tree is slipping?

the vascular cambium is actively growing, and the bark can be peeled easily from the stock piece with little damage

When does bark slip?

in Spring

Approach graft

slice off a small piece from the side of both stocks and graft them together to make one plant

What are the benefits of an approach graft?

prevents the scions and stocks from drying out

Top working graft

grafting where all of the limbs have a graft

When do we use budding most frequently?

When the bark is slipping (spring)

T-bud diagram

Make a T shaped cut in the middle of the new stock and insert the bud

Inverted T-bud

remove the bud from stock, make an upside down T shape in the middle of the new stock and insert bud into upside down T

I-bud graft

Make a cut in the shape of a capital i

Patch bud

remove the bud from stock in an rectangular shape, cut a rectangle in the new stock, and insert the rectangle bud into the new rectangle in the new stock

Ring bud

cut all the way around the stock (just the bark), take the ring off the old stock and insert the ring around the new stock

Flute bud

cut almost all the way around the stock (just the bark), take the almost full ring off the old stock and insert the almost full ring around the new stock

What kind of budding do we use when bark is not slipping?

Chip bud

Chip bud

take bud piece from one stem and cut out piece of stock and discard, replace with bud piece

\--*used when bark is NOT slipping*

Layering

a propagation technique where roots are formed prior to the stem being removed from the parent plant

What form of propagation is most likely to produce a successful plant?

Layering

Where is the phloem located?

between the wood and the bark on a stem of a plant

What is the principle of layering?

Make a part of the plant think it has been removed from the plant by disrupting the phloem (but not the xylem) so that roots will form

What dictates the type of cut made on a plant for layering?

The internal anatomy of a plant

How do we layer on a woody dicot or gymnosperm stem?

By removing a ring of bark around the stem, disrupting the phloem and leaving the xylem unaffected.

Why do we need to remove a ring of bark on a woody dicot or gymnosperm for layering?

So the tree forms roots and doesn't just try and heal the wound in the bark.

How do we layer on a monocot stem?

cut a slit around 1/3 of the way into the stem to disrupt the phloem enough that the plant will form roots at the site of the cut.

Why do we cut 1/3 of the way through a monocot stem to layer?

Because monocots have scattered vascular bundles it isn't possible to just disrupt the phloem like we can for dicots and gymnosperms

Diagram of Layering in Dicots or Gymnosperms

Layering in Monocots

Air layering is done by...

removing a ring of bark on a stem, and packing soil around the new wound and securing it to the branch to allow roots to form into the soil.

* most common layering

Air layering diagram

Simple layering is done by...

bending a stem to bury a part of it

what kinds of plants do we use simple layering on?

plants with flexible stems or vines

Simple layering diagram

Tip layering is done by...

taking the tips of stems and burying them in the ground

Tip layering diagram

Serpentine layering is done by...

A propagation method where the stem of a plant is gently curved at several locations, nicked at each bend, buried in soil, and the terminal end of the shoot being buried is left exposed

Serpentine layering

Trench layering diagram

Trench layering is done by...

placing a plant horizontally after pruning it to be fan-like and covering it in soil to allow new stems to form while still attached to the parent plant.

Mound or stool layering is done by...

mounding soil around the bases of new shoots, excluding light and enhancing root formation.

Mound or stool layering diagram

What is the most common form of layering?

Air Layering

Cutting

a plant part that when removed from the parent plant and placed under the proper environmental conditions forms adventitious roots and/or shoots

What is the most common method of asexual propagation?

Cuttings

What is the main reason cuttings may fail to propagate?

water loss - the cutting dries out before it can propagate into a new plant

How do we minimize water loss in cuttings?

Putting cuttings in a cool humid area, in a humidity chamber, under an intermittent mist system, or using an anti-transpirant on the cutting.

Anti-transpirants

chemicals tha decrease transpiration by forming a film on the leaf surface or by physiologically closing stomata

Intermittent mist system

a propagation system that periodically (every 5 to 30 minutes) sprays a fine mist of water on the cuttings to keep the foliage moist and minimize water loss.

What are the two main hormones that are used on cuttings?

Auxin and Cytokinin

Use of auxin on cuttings stimulates...

adventitious root formation on stem cuttings

What kinds of auxin do we use on plant cuttings?

IBA (most commonly used), NAA (most frequently used), 2 4-D (less used)

Use of cytokinin on cuttings stimulates...

adventitious shoot formation on leaf or root cuttings

What kinds of cytokinin do we use on plant cuttings?

kinetin (commonly used), benzyladenine (BA) (commonly used), Zeatin (rarely used), and pyranylbenzyladenine (PBA) (used in research)

Where do we take plant cuttings from?

any part of the plant (stem, leaf, and root) excluding flowers

What are the types of leaf cuttings?

Leaf bud, Leaf petiole, Leaf blade, and Leaf section

What does a leaf bud cutting need to form?

roots

What does a leaf petiole cutting need to form?

roots and shoots

What does a leaf blade cutting need to form?

roots and shoots

What does a leaf section cutting need to form?

roots and shoots

What are the types of Stem cuttings?

Hardwood, Semi-hardwood, soft/greenwood, Herbaceous, Cane, Rhizome, and Tuber

When do we often take hardwood cuttings?

in the winter

soft wood is...

new growth that is still herbaceous

What is a tuber?

Underground storage stem (Ex. potatoes)

What does every stem cutting have?

a bud - meaning it only needs to form adventitious roots

Where can we take root cuttings from?

Root sections and tuberous roots

What do all stem cuttings need to form?

Roots only