Title: Principles of Propagation by Cuttings
1Chapter 9
- Principles of Propagation by Cuttings
2Biology of Propagation by Cuttings
- Labor costs up to 80 of cost of propagation
- The biology of what actually triggers
adventitious root formation is largely unknown!
3Biology of Propagation by Cuttings
- Adventitious root bud formation
- Stem and leaf-bud cuttings only need to produce
adventitious roots - Root and leaf cuttings need to develop both
adventitious buds adventitious roots
4Biology of Propagation by Cuttings
- Dedifferentiation - the ability of previously
developed, differentiated cells to initiate cell
divisions form new meristems adventitious
roots and buds
5Biology of Propagation by Cuttings
- Adventitious root formation (natural)
- Corn brace roots
6Biology of Propagation by Cuttings
- Adventitious root formation (natural)
- Dracena or Ficus aerial roots
7Biology of Propagation by Cuttings
- Adventitious root formation (natural)
- 2 types
- 1.) Preformed (latent) root initials - develop
naturally on the stem and lie dormant - Ex willow, hydrangea, poplar, coleus, marigold,
tomato, Swedish ivy, pothos - 2.) Wound-induced roots - develop only after the
cutting is made in response to wounding. Formed
de novo ( anew)
8Preformed root initials-Coleus
9Preformed root initials-Pothos
10Preformed root initials-Swedish Ivy
11Preformed root initials-tomato
12Preformed root initials-willow
13Biology of Propagation by Cuttings
- Order of events to produce wound-induced roots
- 1.) outer, injured cells die
- 2.) a necrotic plate forms and seals the wound
(suberin) cork and gum blocks xylem - 3.) parenchyma cells (callus) form behind plate
- 4.) cells near the vascular cambium divide and
produce adventitious roots
14Biology of Propagation by Cuttings
- Exact location of origin of adventitious roots
(still unclear!) - Herbaceous plants originate outside and between
vascular bundles - Note in carnation, roots hit fiber sheath in
stem and cannot penetrate and must grow down
through stem until they emerge from the base of
the cutting - Woody perennials originate from cambium or
young phloem
15Biology of Propagation by Cuttings
- Direct root formation from vascular tissue
- Indirect root formation from callus
- Difficult-to-root species often have a ring of
sclerenchyma cells that block root penetration. - Difficult-to-root species often produce callus
first and then roots from the callus (Indirect
root formation)
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20Biology of Propagation by Cuttings
- Origin of new shoots and roots in leaf cuttings
from - Preformed 1 meristems - cells still meristematic
(rare) - Ex piggyback plant, kalanchoe
- Wound-induced 2 meristems - dedifferentiated
cells - Ex African violet, begonia
21Biology of Propagation by Cuttings
- Limiting factor in leaf cutting propagation is
the formation of adventitious buds NOT
adventitious roots! - Ex rubber tree leaf roots readily but never
forms adventitious shoots
22Biology of Propagation by Cuttings
- Root cuttings
- Need to develop adventitious shoots first then
adventitious roots develop from the adventitious
shoot - Works best on plants that sucker
- Ex apples and crabapples (Malus), lindens
(Tilia), blackberries/raspberries (Rubus) - Note root cuttings produce adventitious shoots
from interior tissue. If you have a periclinal
chimeric plant (i.e. a thornless blackberry),
if you propagate this plant by root cuttings, you
will get plants with thorns
23Biology of Propagation by Cuttings
- Polarity of cuttings
- Distal end nearest the shoot tip shoots
- Proximal end nearest the crown (shoot/root
junction) roots - Note the opposite occurs on root cuttings
- Distal roots
- Proximal shoots
- Polar movement of auxin is an ACTIVE transport
process (will work against gravity if cutting
inverted)
24Biology of Propagation by Cuttings
- Hormonal control of adventitious root bud
formation - Specific root-forming factor discovered by Went
in 1929, called, rhizocaline - Buds effect rooting!
- No buds or dormant buds either inhibit rooting or
have no effect - Leaves effect rooting!
- Presence of leaves increases rooting
25Biology of Propagation by Cuttings
- Auxins
- IAA - naturally occurring (identified in 1935)
- IBA
- NAA
- Exogenous IBA or NAA increases endogenous IAA or
increases tissue sensitivity to IAA
synthetic
26Biology of Propagation by Cuttings
- Root initiation has two stages
- 1.) root initiation
- A.) auxin-active auxin is required for root
formation - B.) auxin-inactive auxin not required for roots
- 2.) Root elongation - auxin not required
27Biology of Propagation by Cuttings
- Cytokinins
- zeatin, kinetin, 2iP, TDZ, BA or BAP
- High auxin/low cytokinin ratio favors
adventitious rooting - Low auxin/high cytokinin ratio favors
adventitious buds/shoots - Difficult-to-root plants often have HIGH
cytokinin levels
28Biology of Propagation by Cuttings
- Gibberellins
- GA (Japan, 1939)
- Causes stem elongation
- Inhibits adventitious root formation (may block
protein production) but depends on the stage of
rooting - Ethylene and Abscisic Acid produce variable
responses.
29Biology of Propagation by Cuttings
- Other compounds
- Salicylate phytohormone (contains salicylic
acid active ingredient in aspirin) from Salix - Growth retardants/inhibitors
- Ancymidal Arrest
- Paclobutrazol Bonzi
- Uniconazole
- Enhance rooting by acting against GA
- Reduce shoot growth, therefore less competition
against root production - None used commercial to improve rooting
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36Biology of Propagation by Cuttings
- Classification of plant rooting responses
- 1.) Plant has all the essential endogenous
substances including auxin. When given proper
environmental conditions, roots will form - 2.) Plant has all the essential endogenous
substances EXCEPT auxin is limiting. Exogenous
auxin application will cause rooting, given
proper environmental conditions - 3.) Some endogenous substances are limiting other
than auxin, therefore external application of
auxin has little response
37Biology of Propagation by Cuttings
- Factors affecting regeneration of plants from
cuttings - Selection and maintenance of stock plants
(for cuttings) - Select material that is easy to root
(physiologically juvenile) - Rejuvenate stock material by serial grafting,
hedging or micropropagation (serial culturing) - Cone of juvenility (oak and beech leaf retention
is an indicator of more juvenile areas)
38Fagus sylvatica (beech)
39Biology of Propagation by Cuttings
- Manipulate the environmental conditions and
physiological status of the stock plant - Water status take cuttings in the morning when
plant material is turgid - Temperature Higher temperatures (54-80F)
better for rooting (however, only a minor role)
40Primrose
41Biology of Propagation by Cuttings
- Light photoperiod/irradiance/quality
specifically as they influence CHOs
accumulation. If photoperiod stimulates floral
development, this will reduce rooting
(photomorphogenic response) - Etiolation of stock plants exclusion of light
- Banding on stock plants localized light
exclusion (Velcro) - Shading growing stock plants under reduced
light conditions. Reduces the production of
lignins and phenolic metabolites normally used to
make lignins instead are used to make roots
42Biology of Propagation by Cuttings
- Girdling - constricting the stem, blocking
downward translocation of CHOs, hormones, etc.
Good on sweetgum, sycamore, pine - Girdling and etiolation best for rooting apples
43Biology of Propagation by Cuttings
- CO2 enrichment mixed responses but if
photosynthesis increases, then increase in CHOs
which helps supply developing roots with energy. - CHOs do NOT regulate rooting but provide
developing roots with energy. A high C/low N
ratio favors root production over shoot production
44Biology of Propagation by Cuttings
- Note for hardwood cuttings, it is best to
select slow-growing lateral shoots over
fast-growing terminal shoots
45Biology of Propagation by Cuttings
- Selection of shoots
- Lateral vs. Terminal shoots
- For softwood cuttings, chose terminal shoots
- For semi-hardwood cuttings, chose lateral shoots
- Basal portion of a shoot best
- More physiologically juvenile
- More preformed root initials
46Biology of Propagation by Cuttings
- Flowering vs. Vegetative shoots
- If easily rooted, it does not matter
-
- If difficult to root, select vegetative shoots
47Biology of Propagation by Cuttings
- Seasonal timing
- If deciduous
- Hardwood when dormant
- Softwood after Spring flush
- Semi-hardwood early summer
- If evergreen
- Broad-leaf cutting after a flush completed
(semi-hardwood) -Spring to fall - Narrow-leaf hardwood best (late fall through
winter)
48Biology of Propagation by Cuttings
- If you do research in this area (even as a
nurseryperson), you should reports finding based
on PHYSIOLOGICAL characteristics and NOT calendar
dates! - Days from budbreak
- Hours of sunlight
- Degree-day chilling or heating units
- Can also use phenology- the art of observing
life cycle phases or activities of plants (and
animals)
49Biology of Propagation by Cuttings
- For efficient use of personnel
- Difficult-to-root plants are taken in winter
- Easy-to-root plants are taken in spring and
summer
50Biology of Propagation by Cuttings
- Treatment of Cuttings
- Storage of cuttings
- Stick immediately or
- mist and hold overnight in a refrigerator
(40-48F) - Long-term storage in a refrigerator with high
humidity ( ethylene inhibitors) - Long-term duration depends on CHO reserves
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52Biology of Propagation by Cuttings
- Auxins
- Middle eastern/European practice - put a grain
seed in the split end of a cutting. - Seed releases auxin as it germinates and
stimulates rooting - An IBA NAA auxin combination is better than
either alone - 2 forms of auxin
- Acid water-insoluble, dissolve in alcohol or
base (KOH) - Salt water soluble form (typically a potassium
salt) - Bacteria and light destroy natural IAA but not
IBA or NAA
53Biology of Propagation by Cuttings
- Note early bud-break and shoot growth of rooted
cuttings is important to overwinter survival of - Acer (maple)
- Cornus (dogwood)
- Hamamelis (witchazel)
- Magnolia (magnolia)
- Prunus (cherry)
- Rhododendron (rhododendron)
- Stewartia (stewartia)
54Biology of Propagation by Cuttings
- Mineral nutrition of cuttings during rooting
- N required for nucleic acids
- Zn is a precursor to auxin
- Leaching of nutrients
- Mist can severely leach nutrients from leafy
cuttings - Easily leached N Mn
- Moderately leached Ca, Mg, S, K
- Slowly leached Fe, Zn, P, Cl
55Biology of Propagation by Cuttings
- Should you add fertilizer to the mist?
- No!
- It will inhibit rooting
- Causes salt build-up or cuttings and equipment
- Increase algae (which reduces aeration and causes
problems with sanitation)
56Biology of Propagation by Cuttings
- Wounding
- Increases callus (which can yield roots)
- Increases ethylene which promotes adventitious
root production - Increases the penetration of exogenous auxins
into the cutting
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59Biology of Propagation by Cuttings
- Manipulation of the environment around cuttings
- Water/humidity
- Minimize transpirational losses
- Water uptake is proportional to the water content
in the medium - Xylem/tracheids typically blocked after cut so
wounding increases diffusion of water into the
cutting
60Biology of Propagation by Cuttings
- Methods to maintain atmospheric water
- Enclosures (tunnels or coldframes)
- Simple and low-cost
- Problem heat is trapped. Shade the plastic or
use white poly. - Best for difficult-to-root species requiring
extended time for rooting (avoid nutrient
leaching) - Contact system
- Lay poly. directly on leafy cuttings after
watering in
61Biology of Propagation by Cuttings
- Intermittent mist
- Developed in the 1940s
- Lowers air temperature (OK)
- Lowers leaf temperature (OK)
- Lowers medium temperature (not good), so should
use with bottom heat - Ex Mist-O-Matic
62Biology of Propagation by Cuttings
- Fog systems
- Maximize humidity
- Water particles stay suspended in air
- Reduces foliage wetting and nutrient leaching
- Reduces disease
- Best on difficult-to-root cuttings
- Helps to acclimate plantlets from tissue culture
63Biology of Propagation by Cuttings
- Temperature
- Optimum 66 - 77F for temperate species
- Optimum 78 - 90F for tropical species
- A 10F drop between day/night is best
- Too high air temps. increase budbreak and
elongation of new shoots (not good) - Root initiation is stimulated by inc. temps.
- Bottom heat best for root initiation then remove
from heat for root development
64Biology of Propagation by Cuttings
- Light (irradiance)
- Low light best for rooting woody plants
(20-30 W/m2 80 - 120 umol/m2/s) -
- Moderate light best for rooting herbaceous plants
(90-100 W/m2 360 - 400 umol/m2/s)
65Biology of Propagation by Cuttings
- Light (photoperiod)
- Long-days or continuous light is best
- Light (quality)
- More red light than far-red light
- Photosynthesis is not required for root formation
as long as CHOs are adequate