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Exam#3 Plant Prop

phytohormones

phytohormones

produced endogenously (within plant),

affects plant in very low concentrations,

provides communication,

site of action =/ site of synthesis

main groups of phytohormones (5)

auxins, gibberellins, cytokinins, ethylene, abscisic acid

other phytohormone groups

salicylic acid, jasmonates, brassinosteroids

plant growth regulators PGR

natural OR synthetic but exogenously applied (added to plant by us/nuserymen)

PLANT GROWTH REGULATOR

all plant hormones are ---- but not all ---- are plant hormones

PGR’s

(Plant growth regulators, plant NEEDS to make these to survive/ complete growth cycles,endogenous)

(PGR’s can also be isolated/synthesized in a lab, therefore, not a ‘naturally’ produced hormones, exogenous)

first discovered phytohormone/ and when?

IAA, 1930s

Indole Acetic Acid (auxin)

basipetally

from tip to base (moves to root crown/basal end)

auxins

define: know synthesis/transport

• meristematic regions= highest concentration (leaf tip/new shoot)

• highest concentration: SAM (apical meristem= most young/juvenile area)

• lowest concentration: crown (crown= proximal, auxin=distal)

• cell elongation and division, root initiation, cambial growth (INITIATES ROOT GROWTH)

• areas of less light (light degrades auxin)

• TRANSPORTED BASIPETALLY (moved DOWN to roots~ via xylem)

common synthetic forms of auxins

IBA and NAA

Indole 3-butyric acid (IBA)

Naphthalene Acetic Acid (NAA) -more potent [for difficult to roots/RECALCITRANT >:) ]

totipotency

ability of a cell to divide and differentiate

~has potential to become entire organism.

dedifferentiation

originally somewhat “specialized” THEN → cell reverts back to active division

auxin is key to --- --- NOT to root elongation

root initiation

(STARTS THE ROOTS!!!)

auxin shapes ----- expression and upregulation of ----

gene, (making more sensitive to auxin) genes

benefits of PGR’s (exogenous application)

• increases % success of rooted cutting

• increases root number and quality

• hastens rooting FASTER ROOTING

• increases rooting UNIFORMITY

powder PGR application

• easy to use

• rooting less uniform

• may involve waste but easy to store

liquid quick dip PGR application

• consistent results

• high concentrations

• 1/2 - 1 in for 5-15 seconds

• uniform rooting

dilute solution soak PGR application

• low auxin concentrations

• 3/4 in to 1 in of basal end of stem

• often left overnight

preformed/latent root initials

develop naturally on the stem and are dormant i.e pothos

(pericycle) already formed!

wound induced roots

develop only after wounding

steps of wound-induced rooting

1. outer/injured cells die

2. necrotic plate forms, sealing the wound

3. parenchyma/callus tissue form behind plate

4. cells near the vascular tissue begin to form adventitious roots

origins of adventitious root/bud/stem formation

preformed meristems (already present pre-formed tissue)

wound induced (initated only by wounding)

limiting factor in leaf cutting propagation

formation of adventitious buds/shoots NOT roots; want whole plant

Chimeras: how to propagate thornless blackberries

you must propagate chimeras by STEM CUTTINGS or you will get plants with thorns/etc

thornless blackberries: gene is found in the outermost layer:

only the __ meristematic layer has the no thorn gene

LI

conditions/equipment for ideal process in producing stem cuttings

• sharp/sanitized shears (no disease/clean cuts)

• cuttings hydrated (turgid)

• uniform size (think for sales)

• treat with rooting compound if needed (how easy is it to propagate?)

stem cutting plant types

• hardwood

• semi-hardwood

• softwood

• herbaceous

Stem cutting: hardwood cuttings

• taken during dormant season

• basal cut just below a node and top cut just above a node (rot)

• 2-3 in

• tops can be waxed: polarity/rot

• at least 2 nodes

deciduous cutting planting

• direct fall planting (mild winters/full growing season)

• initiating roots with bottom heat (taken fall/late winter, planted w heat mats)

• direct spring planting (cutting material gathered during dormancy, wrap in moist stuff til spring)

Stem cuttings:

deciduous cutting types (3)

1. straight/simple

2. heel (small portion of older wood attached)

3. mallet (small section of entire stem of older wood attached)

   ^ not from last flush

narrow leafed evergreen cuttings

• take dormant season

• slow to root/bottom heat

• 4-8in and only last seasons growth

• high light

• low growing species easiest vs upright

• take cuttings from side shoots, strip lower needles, fungicide

• container 4 in deep

broad leafed evergreens

• late spring/midsummer

• 3-8in

• harvest early in day

• 70-80f

softwood cuttings

• cuttings taken in spring during growth

• tissue still soft

• intermittent mist key

• quicker/easier to get adventitious roots

• take early in morning

• 3-5 in

• medial > terminal

herbaceous cuttings

• 3-5in but depends on species

• auxin not usually required

• mist/high humidity

Stem Cuttings: types of herbaceous cuttings

• single eye - alt leaf plant

• double eye - opposite leaf plant

• split node - splitting of node of an opposite leaf plant

• cane - little branching, needs wounding, polarity

chimera

KNOW THIS DEFINITION:

plant with 2 or more genetically dissimilar tissues growing side by side

• higher plants have layered meristems originating from a few cells in the central zone of the SAM (LI, LII, LIII)

• outer layers maintain their integrity because they divide anticlinally

• arise from genetic changes in one or more layers in apical meristem

anticlinally

• cell division perpendicular to surface of a plant organ

• anticlinal division forms a sheet of cells one layer thick while periclinal division results in plant girth!!!!!!!!

mericlinal chimera

genetically different tissue is found in PART OF A SINGLE LAYER of meristem, but not entire layer (LI, LII, LIII)

sectorial chimera

genetically different tissue found in part of ALL meristem layers LI,LII,LIII

periclinal

genetically different tissue makes up ONE ENTIRE LAYER of meristem

which chimera can be reliably propagated, why?

periclinal

mutant tissue is found through an entire meristematic tissue layer

mericlinal and sectorial chimeras can be stabilized as -------------- by the selection of axillary buds

periclinal chimeras

how to propagate chimeras

STEM CUTTINGS

techniques that avoid adventitious bud formation; leaf cutting does not work

(Needs chimera plant’s bud tissue)

leaf bud cuttings

division, layering

budding and grafting

shoot cuttings

techniques that wont produce chimeras

leaf, root, tissue culture (unless contains axillary bud)

axillary buds are

preformed meristems

axillary buds are usually dormant, inhibited by auxin produced by the apical meristem, which is known as apical dominance.

(buds are compressed stems, these embryonic shoots develop exogenously from the outer-cortex layer of the plant at the axillary intersection and eventually grow into new stems.)

leaf bud cuttings, are they stem or leaf cuttings?

Stem cuttings, they contain stem tissue!

leaf cuttings advantages

• little expertise needed

• no need for elaborate facilities

• high humidity better than mist

• well drained substrate required

leaf cutting disadvantages

• doesnt work with chimeras

• small propagules produced, takes a long time

• auxin may inhibit adventitious shoot formation

whole leaf with petiole

whole leaf cutting with petiole attached, ie: peperomia

whole leaf: split vein

cutting the leaf tissues away along veins, planted with portion of vein. ie: rex begonia

leaf section cutting

cutting a section from a whole leaf. ie: snake plant

Vein removal/mid rib vein removal

can be used for any leaves that have a single central vein. cape primrose

leaf cuttings summary

• herbaceous plants

• small pieces of stock plant/smaller prop area, large quantity produced

• polarity matters

Phytohormones are active in a plant in ____ concentrations

LOW

What makes a plant “difficult to root” aka: recalcitrant

1. absent CO-FACTORS

2. mature tissues

How to make a difficult to root plant root?

wounding

exogenous application of auxins

etiolation

Mature- define (different than old)

Ability to sexually reproduce (think fruiting & flowering)

Polarity: Distal & Proximal - DEFINE for root/stem cuttings

root cutting-

proximal= closest to root crown/cone of juvenility

Distal= Furthest from root crown/cone of juvenility (end of root NEAREST to new root tips)

stem cutting-

Proximal= Closest to closest to root crown/cone of juvenility (roots come from here! polarity!)

Distal=Furthest from root crown/cone of juvenility (shoots come from here! polarity!)

Root Cutting- new adventitious shoot formation: 2 locations/types

1. Pericycle: Endogenous or inside the endodermis; contains “additional bud” in YOUNG ROOTS

2. Phellogen: Exogenously; “reparative bud” or cork cambium in OLD ROOTS; replaces the epidermis. wounding required.

Crown- define

Where the roots/stem tissue meet

Know: Where and why the PERICYCLE in a root. (why= why we focus on it?)

pericycle, where: layer under the endodermis, surrounds vascular bundles

pericycle, why: undifferentiated cells, site of new root formation

Cone of juvenility- what is it/ why is it important?

high amounts of meristematic tissue, active cell division, juvenility= ideal propagation material

Leaf Cuttings advantages

1. Little expertise needed

2. No need for elaborate facilities

3. High humidity better than mist

4. Well drained substrate required (1 part peat: 1 part sand, perlite or vermiculite)

Leaf Cutting Disadvantages

1. Doesn’t work with chimeras

2. Small propagules produced

3. takes a long time

4. Auxin may inhibit adventitious shoot formation (auxin inhibits cytokinin)

NAME ALL OF THESE LEAF CUTTING TYPES

whole leaf

whole leaf with petiole

leaf section

Split vein/vein removal leaf cutting

Chimera: generally speaking, what tissue is REQUIRED to maintain chimera expression in propagation & methods (6) to achieve this

BUD TISSUE

methods:

1.Leaf-bud cuttings (bud is present)

2. Division (cut crown)

3. Layering (grown from parent plant)

4. Budding and grafting (splicing?)

5. Tissue culture (involving callus tissue, oogenesis, or somatic embryogenesis/ AXILLARY BUD TISSUE)

Tissue culture is ONLY possible with specific tissues

6. Shoot cuttings (MOST COMMON)

DEFINE: chimera (regarding plants)

Plant with two or more genetically dissimilar tissues growing side by side

CHIMERAS: Know the 3 layers of meristematic tissue of the apical meristem shoot center (SAM= shoot apical meristem)

LI:

LII:

LIII:

LI- epidermis [Tunicate Layer]

LII- endodermis (subepidermal layer) [tunicate layer

LIII- most interior layer that can contain chimera genes [Corpus]

3 kinds of Chimera development- describe the differences (description for where would you find their genetic material)

1. Mericlinal – genetically different tissue is found in part of a single meristem layer

2. Sectorial – genetically different tissue found in part of all meristem layers

3. Periclinal – genetically different tissue makes up one entire meristem layer (LI meristem here)

Of the 3 Chimera types, which one is reliably propagated?

Periclinal- Periclinal chimeras will reliably reproduce themselves because the mutant tissue is continuous through a meristematic layer (axillary buds!!)

Mericlinal and Sectorial chimeras are unstable in propagation (imagine trying to pinpoint where the chimera genes would be found?? this tiny section or this one part of one layer??!)

Chimeras: Remember the two general categories of stem meristems in asexual propagation:

(classify the 2 types of possible formations of meristem)

1. Pericycle: Techniques forming shoots from preformed meristems (Cells are dormant OR already present)

Preformed 1° meristems - cells still meristematic; already there = PRE-FORMED

2. Phellogen: Techniques forming shoots adventitiously (Wound induced requires dedifferentiated cells)

Wound-induced 2° meristems - dedifferentiated cells that become meristematic, needs wounding = REGENERATIVE

Axillary buds are ___ ___ ____ _(what kind of meristem)

Axillary buds are fully formed meristems (preformed)

Best time/conditions to harvest Broad-leafed Evergreen (hardwood cuttings)

1. between 70 to 80 degrees F substrate temperature

2. Harvest cuttings early in the day; maintain turgor

3. Cuttings taken late spring to mid-summer (buds have elongated and stems are firm)

Softwood Cuttings: best time/conditions to harvest

root and shoot temperatures 70 to 80 degrees F

Take cuttings early in the morning; Turgid

Tissue is still soft (little lignification); flexible but breaks when bent

Cuttings taken in spring during flush of growth or during subsequent flushes on multi-flush plants

Herbaceous Cuttings- define herbaceous plant trait:

Typically produce no woody tissue

Types of Herbaceous cuttings: terminal (1) medial (4)

Terminal – contains a terminal bud

Medial – no terminal bud

1. Single-eye – alternate leafed plant

2. Double-eye – opposite leafed plant

3. Split-node – splitting of the node of an opposite leafed plan

Cane - little branching needs wounding

Hardwood Cuttings: DEFINE basal cut

Basal cut- cut closest to basal stem (crown) just below a node.

top cut just above a node (to prevent rot!)

Hardwood cuttings: why would you wax the tops? why wouldn’t you wax the bottoms?

Tops can be waxed preventing desiccation and rot (hollow pithed species);

also polarity (shows which end is up)

Bottom waxing will prevent root initials from penetrating into soil

hardwood cuttings: three types

1. Mallet – small section of entire stem of older wood attached; not from last flush .

2. Heel – small portion of older wood attached; not from last flush of growth

3. Straight or simple

General Process of Producing Stem Cuttings

Sharp, sanitized shears/knife

Keep cuttings hydrated

Trim cuttings to a standard size - critical for uniform success

Treat with rooting compound (PGR), if needed

Auxin Application Methods

Liquid Quick Dip, Talc or Powder Dip, and Dilute Soak, Gel (Eakes hates this tho~ so wasteful)

Stem Cutting Types (4)

(plant type characteristics that help decide what stem cutting you may use) is it a tree? is it a rose?

• Hardwood cuttings (Deciduous species & Narrow-leafed evergreen species)

winter harvest- evergreen pines/tougher leaf drop winter dormant

• Semi-hardwood cuttings (Broad-leafed evergreens & Leafed deciduous species )

spring-midsummer harvest- less tough than pines, maybe oak trees etc.

• Softwood cuttings

spring harvest- SOFTER issue, still green! think a rosemary bush!

• Herbaceous/tropical cuttings (what we have been doing in Lab)

SUPER DELICATE- think seedum

Basal Cut Position on Stem Cuttings: Basal cut should be _____

Basal should be at an angle

Why should basal should be at an angle?

Position of cut can impact adventitious root formation (more surface area), remember polarity!

“Nodal cut” or “nodal cutting” has the basal cut about ____ below bottom node. why?

basal cut about 1/8” below bottom node [bud(s)]

Helps prevent fungal rot

Insures a bud is below substrate surface

“Internodal cut” or “internodal cutting” has the basal cut about ____ below bottom node. why?

Does not insure bud below substrate surface

Does not reduce fungal growth in wide-pithed or hollow-pithed species

Location of Adventitious Root Formation:

•Herbaceous plants -originate outside and between vascular bundles

•Woody perennials - originate from cambium or young phloem

Summary of Wound-Induced Rooting (4 stages)

1. Outer/Injured cells die

2. Necrotic plate forms, sealing the wound (suberized=waterproof)

3. Parenchyma cells (callus tissue) begins to form behind the plate

4. Cells near the vascular tissue (i.e. phloem parenchyma) begin to form adventitious roots (c)

Auxin (PGR phytohormone) what does it do?

INITIATE ROOT GROWTH (inhibits cytokinin)

Stimulates cell elongation

Involved in cell division of root initials

Synthesized in meristematic regions, apical meristems, and actively growing organs

(embryos of developing seed)

Gibberellins (PGR/phytohormone) what does it do?

Stem/internode elongation,

Flower initiation and sex expression (male flowers promoted, i.e. Cucumis)

speed of seed germination

Causes parthenocarpic fruit production (seedless fruit)

Ethylene (PGR phytohormone) what does it do?

Plant decrease in longitudinal growth, thickening of the shoot → switch to horizontal growth

Stimulates fruit ripening ,

Flower initiation

Changing sex expression of flowers (female flowers in cucumber and pumpkins; increased yield)

Abscisic Acid (PGR phytohormone) what does it do?

ABA (natural, no synthetic forms available)mostly in mature leaves, but also roots~ Transported in both xylem and phloem

MOST IMPORTANT:

Important signal for plant water relations, stomatal activity (STIMULATES STOMATA COLSURE) responds to CO2 concentration and light/darkness

Regulation of seed development, accumulation of seed proteins; preventing “precocious seed germination” (premature seed germination, like within a tomato)

Stem Formation for Root Cuttings: ideal cutting candidates?

Plants that sucker are the best candidates for root cuttings

physiologically, how does the growth process differ in Stem/Leaf Cuttings VS Root Cuttings? (describe first stages for both)

Stem/Leaf Cuttings: Develop/encourage root growth first, then shoot growth

Root Cuttings: Develop/encourage shoot growth first, then more root growth

Why is Etiolation used for propagation

prevent tissue from lignifying.

young/juvenile tissue is more responsive to PGR’s

Light exclusion from tissue where adventitious roots desired (“blanching” or “etiolation”)

in a DICOT stem, where are the xylem and phloem oriented in the vascular bundles? How are the vascular bundles organized?

xylem=inner layer (closer to pith)

phloem=outer layers (further from pith)

vascular bundles= organized in a ring outside of pith

in a MONOCOT stem, where are the xylem and phloem oriented in the vascular bundles? How are the vascular bundles organized?

xylem= inner portion of vascular bundles, surrounded by phloem

phloem= bulk of the vascular bundle, contains xylem

vascular bundles= random organization

DEFINE: Totipotency

innate ability of a plant cell to create an entirely new plant

AUXIN: Root Formation and Growth- initiation phase, know how to describe initiation phase.

Wound response - Dedifferentiation of cells at wound (cambium/cortex near phloem)

Proliferation of parenchyma cells - callus, formation of meristematic tissue (root initials)

Formation of root primordia (very beginning)/xylem vessels

AUXIN: Root Formation and Growth- elongation phase, know how to describe elongation.

REMEMBER~ Auxin relates to roots!

Root initiation - along the cambium/cortex tissue near phloem; emergence of vessel growth

Root and vessel enlargement - connection to stem vessels