chapter 9 principles of propagation by cuttings. biology of propagation by cuttings labor costs = up...

Chapter 9Chapter 9Principles of Propagation by Principles of Propagation by

CuttingsCuttings

Biology of Propagation by CuttingsBiology of Propagation by Cuttings

• Labor costs = up to 80% of cost of Labor costs = up to 80% of cost of propagationpropagation

• The biology of what actually triggers The biology of what actually triggers adventitious root formation is largely adventitious root formation is largely unknownunknown!!


• Adventitious root & bud formationAdventitious root & bud formation– Stem and leaf-bud cuttings only need to Stem and leaf-bud cuttings only need to

produce adventitious rootsproduce adventitious roots

– Root and leaf cuttings need to develop Root and leaf cuttings need to develop bothboth adventitious buds & adventitious rootsadventitious buds & adventitious roots


• DedifferentiationDedifferentiation - the ability of - the ability of previously developed, differentiated cells previously developed, differentiated cells to initiate cell divisions & form new to initiate cell divisions & form new meristems = adventitious roots and budsmeristems = adventitious roots and buds


• Adventitious root formation (natural)Adventitious root formation (natural)– Corn: brace rootsCorn: brace roots


• Adventitious root formation (natural)Adventitious root formation (natural)– DracenaDracena or or FicusFicus: aerial roots: aerial roots


• Adventitious root formation (natural)Adventitious root formation (natural)– 2 types:2 types:

1.) 1.) PreformedPreformed (latent) root initials - develop (latent) root initials - develop naturally on the stem and lie dormantnaturally on the stem and lie dormant

• Ex: willow, hydrangea, poplar, coleus, marigold, Ex: willow, hydrangea, poplar, coleus, marigold, tomato, Swedish ivy, pothostomato, Swedish ivy, pothos

2.) Wound-induced roots - develop only after the 2.) Wound-induced roots - develop only after the cutting is made in response to wounding. cutting is made in response to wounding. Formed “de novo” (= “anew”)Formed “de novo” (= “anew”)

Preformed root initials-ColeusPreformed root initials-Coleus

Preformed root initials-PothosPreformed root initials-Pothos

Preformed root initials-Preformed root initials-Swedish IvySwedish Ivy

Preformed root initials-tomatoPreformed root initials-tomato

Preformed root initials-willowPreformed root initials-willow


• Order of events to produce wound-induced Order of events to produce wound-induced rootsroots

– 1.) outer, injured cells die1.) outer, injured cells die

– 2.) a necrotic plate forms and seals the wound 2.) a necrotic plate forms and seals the wound

(suberin) = cork and gum blocks xylem(suberin) = cork and gum blocks xylem

– 3.) parenchyma cells (callus) form behind plate3.) parenchyma cells (callus) form behind plate

– 4.) cells near the vascular cambium divide and 4.) cells near the vascular cambium divide and

produce adventitious rootsproduce adventitious roots


• Exact location of origin of adventitious roots Exact location of origin of adventitious roots (still unclear!)(still unclear!)– Herbaceous plantsHerbaceous plants = originate outside and between = originate outside and between

vascular bundlesvascular bundles• Note: in carnation, roots hit fiber sheath in stem and Note: in carnation, roots hit fiber sheath in stem and

cannot penetrate and must grow down through stem until cannot penetrate and must grow down through stem until they emerge from the base of the cuttingthey emerge from the base of the cutting

– Woody perennialsWoody perennials = originate from cambium or = originate from cambium or young phloemyoung phloem


• Direct root formation from vascular tissueDirect root formation from vascular tissue

• Indirect root formation from callusIndirect root formation from callus

• Difficult-to-root species often have a ring of Difficult-to-root species often have a ring of sclerenchyma cells that block root penetration.sclerenchyma cells that block root penetration.

• Difficult-to-root species often produce callus Difficult-to-root species often produce callus first and then roots from the callus (Indirect first and then roots from the callus (Indirect root formation)root formation)


• Origin of new shoots and roots in leaf cuttings Origin of new shoots and roots in leaf cuttings from:from:

– Preformed 1° meristems - cells still meristematic Preformed 1° meristems - cells still meristematic (rare)(rare)Ex: piggyback plant, kalanchoeEx: piggyback plant, kalanchoe

– Wound-induced 2° meristems - dedifferentiated cellsWound-induced 2° meristems - dedifferentiated cellsEx: African violet, begoniaEx: African violet, begonia


• Limiting factor in leaf cutting Limiting factor in leaf cutting propagation is the formation of propagation is the formation of adventitious buds adventitious buds NOTNOT adventitious adventitious roots!roots!

Ex: rubber tree leaf roots readily but Ex: rubber tree leaf roots readily but never forms adventitious shootsnever forms adventitious shoots

Biology of Propagation by CuttingsBiology 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


• 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)


• Hormonal control of adventitious root& Hormonal control of adventitious root& bud formationbud formation– Specific root-forming factor discovered by Specific root-forming factor discovered by

Went in 1929, called, “rhizocaline”Went in 1929, called, “rhizocaline”– Buds effect rooting! Buds effect rooting!

• No buds or dormant buds either inhibit rooting No buds or dormant buds either inhibit rooting or have no effector have no effect

– Leaves effect rooting! Leaves effect rooting! • Presence of leaves increases rootingPresence of leaves increases rooting


• AuxinsAuxins– IAA - naturally occurring (identified in 1935)IAA - naturally occurring (identified in 1935)– IBA IBA – NAA NAA

– Exogenous IBA or NAA increases endogenous Exogenous IBA or NAA increases endogenous IAA or increases tissue sensitivity to IAAIAA or increases tissue sensitivity to IAA

syntheticsynthetic


• Root initiation has two stages:Root initiation has two stages:

1.) root initiation1.) root initiation– A.) auxin-active: auxin is required for root A.) auxin-active: auxin is required for root

formationformation– B.) auxin-inactive: auxin not required for rootsB.) auxin-inactive: auxin not required for roots

2.) Root elongation - auxin not required2.) Root elongation - auxin not required


• CytokininsCytokinins– zeatin, kinetin, 2iP, TDZ, BA or BAPzeatin, kinetin, 2iP, TDZ, BA or BAP– High auxin/low cytokinin ratio favors High auxin/low cytokinin ratio favors

adventitious rootingadventitious rooting– Low auxin/high cytokinin ratio favors Low auxin/high cytokinin ratio favors

adventitious buds/shootsadventitious buds/shoots

– Difficult-to-root plants often have HIGH Difficult-to-root plants often have HIGH cytokinin levelscytokinin levels


• GibberellinsGibberellins– GA (Japan, 1939)GA (Japan, 1939)– Causes stem elongationCauses stem elongation– Inhibits adventitious root formation (may Inhibits adventitious root formation (may

block protein production) but depends on block protein production) but depends on the stage of rootingthe stage of rooting

• Ethylene and Abscisic Acid produce Ethylene and Abscisic Acid produce variable responses.variable responses.


• 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

Biology of Propagation by CuttingsBiology 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


• Factors affecting regeneration of plants from Factors affecting regeneration of plants from cuttingscuttings– Selection and maintenance of stock plants Selection and maintenance of stock plants

(for cuttings)(for cuttings)• Select material that is easy to root (physiologically Select material that is easy to root (physiologically

juvenile)juvenile)• Rejuvenate stock material by serial grafting, hedging or Rejuvenate stock material by serial grafting, hedging or

micropropagation (serial culturing)micropropagation (serial culturing)• Cone of juvenility (oak and beech leaf retention is an Cone of juvenility (oak and beech leaf retention is an

indicator of more juvenile areas)indicator of more juvenile areas)

Fagus sylvaticaFagus sylvatica (beech) (beech)


• Manipulate the environmental conditions Manipulate the environmental conditions and physiological status of the stock plantand physiological status of the stock plant

– Water statusWater status: take cuttings in the morning : take cuttings in the morning when plant material is turgidwhen plant material is turgid

– TemperatureTemperature: Higher temperatures (54-: Higher temperatures (54-80°F) better for rooting (however, only a 80°F) better for rooting (however, only a minor role)minor role)

PrimrosePrimrose

Biology of Propagation by CuttingsBiology of Propagation by Cuttings– Light: photoperiod/irradiance/quality specifically

as they influence CHO’s 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


• GirdlingGirdling - constricting the stem, blocking - constricting the stem, blocking downward translocation of CHO’s, downward translocation of CHO’s, hormones, etc. Good on sweetgum, hormones, etc. Good on sweetgum, sycamore, pinesycamore, pine

• Girdling and etiolation best for rooting Girdling and etiolation best for rooting applesapples


• COCO22 enrichment = mixed responses but if enrichment = mixed responses but if

photosynthesis increases, then increase in photosynthesis increases, then increase in CHO’s which helps supply developing roots CHO’s which helps supply developing roots with energy.with energy.

• CHO’s do NOT regulate rooting but provide CHO’s do NOT regulate rooting but provide developing roots with energy. A high C/low N developing roots with energy. A high C/low N ratio favors root production over shoot ratio favors root production over shoot productionproduction


• NoteNote: for hardwood cuttings, it is best to : for hardwood cuttings, it is best to select slow-growing lateral shoots over select slow-growing lateral shoots over fast-growing terminal shootsfast-growing terminal shoots


• Selection of shootsSelection of shoots

• Lateral vs. Terminal shoots:Lateral vs. Terminal shoots:– For softwood cuttings, chose terminal shootsFor softwood cuttings, chose terminal shoots

– For semi-hardwood cuttings, chose lateral shootsFor semi-hardwood cuttings, chose lateral shoots

• Basal portion of a shoot bestBasal portion of a shoot best– More physiologically juvenileMore physiologically juvenile

– More preformed root initialsMore preformed root initials


• Flowering vs. Vegetative shootsFlowering vs. Vegetative shoots

– If easily rooted, it does not matterIf easily rooted, it does not matter

– If difficult to root, select vegetative shootsIf difficult to root, select vegetative shoots


• Seasonal timing:Seasonal timing:

– If deciduous:If deciduous:

• Hardwood = when dormantHardwood = when dormant

• Softwood = after Spring flushSoftwood = after Spring flush

• Semi-hardwood = early summerSemi-hardwood = early summer

– If evergreen:If evergreen:

• Broad-leaf = cutting after a flush completed (semi-Broad-leaf = cutting after a flush completed (semi-

hardwood) -Spring to fallhardwood) -Spring to fall

• Narrow-leaf = hardwood best (late fall through winter)Narrow-leaf = hardwood best (late fall through winter)


• If you do research in this area (even as a If you do research in this area (even as a nurseryperson), you should reports nurseryperson), you should reports finding based on finding based on PHYSIOLOGICALPHYSIOLOGICAL characteristics and characteristics and NOTNOT calendar dates! calendar dates!

• Days from budbreakDays from budbreak• Hours of sunlightHours of sunlight• Degree-day chilling or heating unitsDegree-day chilling or heating units

• Can also use “phenology”- the art of Can also use “phenology”- the art of observing life cycle phases or activities of observing life cycle phases or activities of plants (and animals)plants (and animals)


• For efficient use of personnel:For efficient use of personnel:

– Difficult-to-root plants are taken in winterDifficult-to-root plants are taken in winter

– Easy-to-root plants are taken in spring and Easy-to-root plants are taken in spring and summersummer


• Treatment of Cuttings:Treatment of Cuttings:– Storage of cuttingsStorage of cuttings

• Stick immediately orStick immediately or

• mist and hold overnight in a refrigerator (40-mist and hold overnight in a refrigerator (40-48°F)48°F)

• Long-term storage in a refrigerator with high Long-term storage in a refrigerator with high humidity (+ ethylene inhibitors)humidity (+ ethylene inhibitors)

• Long-term duration depends on CHO reservesLong-term duration depends on CHO reserves


– AuxinsAuxins

• Middle eastern/European practice - put a grain seed in the Middle eastern/European practice - put a grain seed in the

split end of a cutting. split end of a cutting.

• Seed releases auxin as it germinates and stimulates rootingSeed releases auxin as it germinates and stimulates rooting

• An IBA +NAA auxin combination is better than either aloneAn IBA +NAA auxin combination is better than either alone

• 2 forms of auxin2 forms of auxin

– Acid = water-insoluble, dissolve in alcohol or base (KOH)Acid = water-insoluble, dissolve in alcohol or base (KOH)

– Salt = water soluble form (typically a potassium salt)Salt = water soluble form (typically a potassium salt)

• Bacteria and light destroy natural IAA but not IBA or NAABacteria and light destroy natural IAA but not IBA or NAA


• Note: early bud-break and shoot growth of rooted Note: early bud-break and shoot growth of rooted cuttings is important to cuttings is important to overwinteroverwinter survival of: survival of:– Acer Acer (“maple”)(“maple”)

– Cornus Cornus (“dogwood”)(“dogwood”)

– HamamelisHamamelis (“witchazel”) (“witchazel”)

– Magnolia Magnolia (“magnolia”)(“magnolia”)

– PrunusPrunus (“cherry”) (“cherry”)

– RhododendronRhododendron (“rhododendron”) (“rhododendron”)

– StewartiaStewartia (“stewartia”) (“stewartia”)


• Mineral nutrition of cuttings during rootingMineral nutrition of cuttings during rooting

– N required for nucleic acidsN required for nucleic acids

– Zn is a precursor to auxinZn is a precursor to auxin

• Leaching of nutrients:Leaching of nutrients:

– Mist can severely leach nutrients from leafy cuttingsMist can severely leach nutrients from leafy cuttings

• Easily leached: N & MnEasily leached: N & Mn

• Moderately leached: Ca, Mg, S, KModerately leached: Ca, Mg, S, K

• Slowly leached: Fe, Zn, P, ClSlowly leached: Fe, Zn, P, Cl


• Should you add fertilizer to the mist?Should you add fertilizer to the mist?

– No! No!

– It will inhibit rootingIt will inhibit rooting

– Causes salt build-up or cuttings and equipmentCauses salt build-up or cuttings and equipment

– Increase algae (which reduces aeration and causes Increase algae (which reduces aeration and causes

problems with sanitation)problems with sanitation)


• WoundingWounding– Increases callus (which can yield roots)Increases callus (which can yield roots)

– Increases ethylene which promotes Increases ethylene which promotes adventitious root productionadventitious root production

– Increases the penetration of exogenous Increases the penetration of exogenous auxins into the cuttingauxins into the cutting


• Manipulation of the environment around Manipulation of the environment around cuttings:cuttings:– Water/humidityWater/humidity

• Minimize transpirational lossesMinimize transpirational losses

• Water uptake is proportional to the water Water uptake is proportional to the water content in the mediumcontent in the medium

• Xylem/tracheids typically blocked after cut so Xylem/tracheids typically blocked after cut so wounding increases diffusion of water into the wounding increases diffusion of water into the cuttingcutting


• Methods to maintain atmospheric waterMethods to maintain atmospheric water

– Enclosures (tunnels or coldframes)Enclosures (tunnels or coldframes)

• Simple and low-costSimple and low-cost

• Problem: heat is trapped. Shade the plastic or use white poly.Problem: heat is trapped. Shade the plastic or use white poly.

• Best for difficult-to-root species requiring extended time for Best for difficult-to-root species requiring extended time for

rooting (avoid nutrient leaching)rooting (avoid nutrient leaching)

– Contact systemContact system

• Lay poly. directly on leafy cuttings after watering inLay poly. directly on leafy cuttings after watering in


• Intermittent mistIntermittent mist

– Developed in the 1940’sDeveloped in the 1940’s

– Lowers air temperature (OK)Lowers air temperature (OK)

– Lowers leaf temperature (OK)Lowers leaf temperature (OK)

– Lowers medium temperature (not good), so should Lowers medium temperature (not good), so should

use with bottom heatuse with bottom heat

– Ex: Mist-O-MaticEx: Mist-O-Matic


• Fog systemsFog systems– Maximize humidityMaximize humidity– Water particles stay suspended in airWater particles stay suspended in air– Reduces foliage wetting and nutrient leachingReduces foliage wetting and nutrient leaching– Reduces disease Reduces disease – Best on difficult-to-root cuttingsBest on difficult-to-root cuttings– Helps to acclimate plantlets from tissue cultureHelps to acclimate plantlets from tissue culture


• TemperatureTemperature– Optimum = 66 - 77°F for temperate speciesOptimum = 66 - 77°F for temperate species

– Optimum = 78 - 90°F for tropical speciesOptimum = 78 - 90°F for tropical species

– A 10°F drop between day/night is bestA 10°F drop between day/night is best

– Too high air temps. increase budbreak and Too high air temps. increase budbreak and elongation of new shoots (not good)elongation of new shoots (not good)

– Root initiation is stimulated by inc. temps.Root initiation is stimulated by inc. temps.

– Bottom heat best for root initiation then remove Bottom heat best for root initiation then remove from heat for root developmentfrom heat for root development


• Light (irradiance)Light (irradiance)

– Low light best for rooting woody plants Low light best for rooting woody plants (20-30 W/m(20-30 W/m2 2 = 80 - 120 umol/m = 80 - 120 umol/m22/s)/s)

– Moderate light best for rooting herbaceous Moderate light best for rooting herbaceous plants (90-100 W/mplants (90-100 W/m22 = 360 - 400 umol/m = 360 - 400 umol/m22/s)/s)

http://www.fb.u-tokai.ac.jp/WWW/hoshi/env/light.html


• Light (photoperiod)Light (photoperiod)– Long-days or continuous light is bestLong-days or continuous light is best

• Light (quality)Light (quality)– More red light than far-red lightMore red light than far-red light

• Photosynthesis is not required for root Photosynthesis is not required for root formation as long as CHO’s are adequateformation as long as CHO’s are adequate

chapter 9 principles of propagation by cuttings. biology of propagation by cuttings labor costs = up...

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