Anatomy and physiology of adventitious root...
Transcript of Anatomy and physiology of adventitious root...
Anatomy and physiology of adventitious root formation Prof. Dr. Károly Hrotkó
SZIU Faculty of Horticultural Science
Anatomy and physiology of adventitious root formation
Autovegetative propagation in nursery 2
Widespread used autovegetative propagation methods in nurseries Cuttings (green cuttings, softwood cuttings, semi-
hardwood cuttings: leafy cuttings): ornamental shrubs and trees, conifers, some rootstocks
Hardwood cuttings: ornamental shrubs and trees, berry fruits, some rootstocks, forest plants, energy plants
Micropropagation: ornamental shrubs and trees, conifers, some rootstocks
Layerage: rootstocks, berry fruits, some ornamentals Markottage: using suckers (raspberry) Root cuttings: very few application (some berry fruits,
Rhus, etc.)
Autovegetative propagation in nursery 3
Faiskola bevezető előadás
Dr. Hrotkó Károly
Mist propagation (leafy cuttings)
Hardwood cuttings in outdoor beds
Stoolbed
Micropropagation
Autovegetative propagation in nursery 6
Possible application at plants developing propagating organs:
plantlets, (strawberry) stolons, root suckers
plants developing preformed roots (Ribes, some Prunus sp., Malus, Salix, Populus)
plants developing adventitious roots (Ligustrum, Forsythia, Philadelphus)
plants developing adventive buds, shoots on root part (root cuttings)
Autovegetative propagation in nursery 7
Growth of preformed roots on Salix caprea
Plantlets for propagfation of strawberry
Autovegetative propagation in nursery 8
Preformed roots Colt cherry rootstock
Apple (J-TE-D)
Autovegetative propagation in nursery 9
Possible application at plants developing propagating organs:
plantlets, (strawberry) stolons, root suckers
plants developing preformed roots (Ribes, some Prunus, Malus, Salix, Populus)
plants developing easily adventitious roots (Ligustrum, Forsythia, Philadelphus)
plants developing adventive buds, shoots on root part (root cuttings)
Autovegetative propagation in nursery 10
Schedule of reparative regeneration in autovegetative propagation methods Cuttings (hardwood or leafy cuttings):
regeneration after separation of propagationg material
Layerage (layering, stooling): regeneration on stockplant separation after rooting of shoots
Markottage, suckers, propagating organs: regeneration on stockplant separation after rooting of shoots
Micropropagation: regeneration after separation of propagationg material, in-vitro conditions, followed by acclimatization and hardening off
Anatomy of adventive root formation
Autovegetative propagation in nursery 12
← terminal cutting
← basal cutting
Hardwood cutting
Autovegetative propagation in nursery 13
Shoot meristem in shoot tip Section of subterminal growth
Rhytidom typical to species, leaf fall, → leafless shoot
Secondary expansion, lignification
Secondary expansion, complete cambial ring, formation of secondary xylem schlerenchyma (lignification starts)
Cross section of an angiosperm,
dicotyledonous, secondary expansion stem periderm
paracambium
yearring
Tilia cordata
littleleaf linden
MALVACEAE
corky
parenchyma
flared
primary pith
ray
xylem cambium
late
plate
early
plate
soft phloem hard phloem pith
Autovegetative propagation in nursery 15
Possible position of new roots
Autovegetative propagation in nursery 17
Hormonal compounds in root initiation
Adventive root formation in the stem
Activating factors - ceased correlative balance due to cutting separation
- accumulation of hormonal compounds
- environmental conditions (etiolation, blanching, soil cover)
Root initiation process 1. dedifferenciating cells, cell multiplication 2. formation of root initials
- auxin sensitive stage
- auxin inaktiv stage
3. formation of root primordium
4. root elongation and growth
Role of auxine compounds
Auxin - controls rooting in early stage of initiation
- bazipetal auxine transport is important
- decreasing concentration in the later stage of rooting
- interaction between native (IES) and exogen applied heteroauxins
- shoot tips, buds, leaves are necessary
Rizocalin theory (Bouillene & Bouillene-Walrand 1955)
root initiating complex consisting of:
a) specifikus factor from leaves or buds (o-dihidroxi-fenol)
b) non-specific factor (auxin)
c) specific enzim (polifenol-oxidase PPO)
Stages of root initiation
Rhizocalin theory (Bouillene & Bouillene-Walrand 1955)
Application of auxine in practice
Auxine compounds : IAA, NAA, IBA
Commercial powder preparations (talcum, bentonit)
Dilute solution Soaking method (50 – 150 ppm)
Quick dip (concentrated solution in 50% alcohol)
K + salt formulation (water soluble form)
Spray, paints.
• Turgor, water content.
• Temperature.
• Light - shading, etiolation.
• Nutrition.
• CO2 enrichment.
Stockplant management for cutting propagation
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 25
Water supply of stockplant and water content of cuttings Optimal water supply is required.
Taking cuttings earlier (before 9 am) results higher turgor.
Water deficit of stockplants results low rooting capacity and susceptibility to infections.
Water loss of hardwood cuttings improves the uptake of hormonal soultion.
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 26
16.05.2008
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Dynamics of transpiration of
leaves on Prunus avium
in May 2008.
(2008. 05. 16. és 2008. 05. 26.)
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 27
Water content
influence the
rooting of cuttings;
above 50% more
favorable
Sainte Julien GF 655/2
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40 45 50 55 60
Water (%)
Rooti
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%)
Gyökeresedés
Lineáris (Gyökeresedés)
Rooting of plum hardwood cuttings related to
water content of cuttings
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 28
PPO-
activity
cold unit
water
content leaf fall POD-activity
phenolics
sprouting rooting
temperature
Effects on rooting of plum rootstocks hardwood cuttings
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 29
Marianna GF 8-1
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-250 0 250 500 750 1000 1250 1500 1750 2000
Cold unit (CU)
ro
oti
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(%
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gyökeresedés
Lineáris (gyökeresedés)
– No direct link
between dayly
average
temperature and
rooting
– Low cold unit
quantity befora
taking cuttings
(below 500 CU) is
more favorable
Temperature and cold unit (CU) on plum rootstocks’
hardwood cuttings
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 30
Rooting of plum rootstocks’ hardwood cuttings
Phenolics and
rooting
– favorable:
Fehér besztercei:
above 10 μg/mg
St. Julien GF 655/2:
10-30 μg/mg
Marianna GF 8-1:
15-40 μg/mg
Marianna GF 8-1
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phenol content in buds (μg/mg)
roo
tin
g (
%)
Gyökeresedés
Polinom. (Gyökeresedés)
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POD activity and
rooting
– Low activity is more
favourable
– Fehér besztercei (bud)
St. Julien GF 655/2
(cutting): under 4 U/mg,
Marianna GF 8-1
(cutting): under 3 U/mg
Marianna 8-1
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POD activity (U/mg protein)
Rooti
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%)
Gyökeresedés
Lineáris (Gyökeresedés)
Rooting of plum hardwood cuttings
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 32
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taking of cuttings (date)
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tin
g (
%)
Fehér besztercei
Sainte Julien GF
655/2
Marianna GF 8-1
Polinom. (Fehér
besztercei)
Polinom. (Marianna
GF 8-1)
Polinom. (Sainte
Julien GF 655/2)
Autovegetative propagation in nursery 33
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 34
Effect of light on stockplants Daylength
- affetc photosysnthesis: carbohidrate accumulation - fotomorfogenetic effect : increasing daylength affect positive the vegetative growth and rooting of Chrisanthemum.
Wawelength no consistent results: red light stimulate the phytochrom system and rooting, but some results indicate that blue light also positive.
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Etiolation and shading of stockplants Etiolation: excluded solar radiation. During preconditioning different level of shading
is more applied in practice. Local etiolation using black strips or Alu folie. Effect
- starch accumulation, - reduced formation of schlerenchima, - reduced lignin production – phenolics may be used for rooting, - etiolated tissue react more efficient to auxine treatments.
Effect of etiolation on stem – Tilia cordata
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 37
Rejuvenalization
grafting subsequently
on seedlings →
Etiolated and shaded
stockplants
0
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kontroll talajjal takart Raschel háló átlátszó fólia fekete fólia
gyökeresedés %
Effect of preconditioning on rooting of MM.106 cuttings
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Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 40
Nutrition of stockplants Shoot mass and its nutrient content is determining
to the regeneration process (related to the anatomy structure too)
Factors of nutrient balance during rooting: + absorption from substrate (no importance!) + assimilation (only leafy cuttings!) - respiration during rooting (increase due auxine application) - leaching due to irrigation, mist application
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Principles of nitrogen and carbohydrate metabolism in cuttings Lack of roots – no nitrogen uptake and assimilation
Amino acid sources for root formation: - Amino acid reserve - proteolitic processes (decomposition of proteins)
Carbohydrates: energy reserves and sources for structural carbohydrates (cellulose)
Optimal concentration of non-structural carbohydrates (sugar, starch) is required for rooting
Starch content test on hardwood cuttings (jódos-jódkáli 0,2%)
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 42
Importance of Carbohydrate / Nitrogen ratio Carbohydrates: energy reserves and sources for
structural carbohydrates (cellulose)
Indirect effects!
Higher C / N ratio in stockplant shoots is favourable.
Exceed nitrogen reduction decreases the shoot (cuttings) production.
In thin shoots, secondary shoots the C/N ratio and rooting is higher.
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 43
Management of stockplant in order to improve C/N ratio in practice Decreased N- supply; increased K and P supply
Root restriction: close planting, root pruning
Pruning back the primary shoots (increased C/N ratio in secondary shoots)
Moving away from shoot basis C/N ratio decreases
Maintaining healthy leaf surface
Positive effect of ringing, etiolation
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Role of other nutrients in rooting process Ca - activates peroxidase, essential for growing of root
primordium
Zn - cathalitic effect on triptophan synthesys → formation of native auxine
Mn - activates oxidative enzymes
B - influences the permeability of membrane, sugar transport, activates enzyme, carbohydrate metabolism, metabolism of phenolics, formation of auxine, and nucleic acids
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 45
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treatments Rooting (%) Cuttings’ weight
(g)
Kelpak on stockplant
+ IBA 0.2% on cuttings
77,1 a 3,77 b
Wuxal Ascofol on stockplants
+ IBA 0.2% on cuttings
66,7 a 2,86 a
Pentakeep-V on stockplants
+ IVS 0.2% on cuttings
60,4 a 2,96 ab
Untreated stockplant
+ IVS 0.2% on cuttings
75,0 a 2,88 a
Effect of biostimulator treatments of stockplants
on cuttings’ quality (Szabó et al. 2011)
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 47
Shoot position and type of cuttings is related to nutrient content Considerable morphological and nutrient content
differences along the shoot from basis to shoot tip. Secondary shoots, branches root better, but
consider plagiotropic shoots. Basal cuttings generally root better:
- more ripe and lignificated shoots, higher C/N ratio, - meristematic cell groups in branch collar, - number of preformed roots considerable decreases towards the shoot tip.
Shoots with flower buds root less (blueberry, Abelia, Ligustrum, Ilex, etc.)
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CO2 enrichment Increased photosynthese – more shoots appropriate
for cuttings.
Only in closed systems (greenhouse) is possible.
In winter effectivity should be increased usin supplementary lighting.
• Mentain leaf water content and turgor.
• Water loss through transpiration activity water supply
• Photosynthetic activity and solar radiation transpiration to avoid heat stress
• Optimal temparature in rooting zone
Environmental conditions during rooting of leafy cuttings
Prof. Dr. Hrotkó Károly Seed germination….. 50
Autovegetative propagation in nursery 51
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Autovegetative propagation in nursery
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Autovegetative propagation in nursery
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Autovegetative propagation in nursery
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Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 57
Difficulties in water management of leafy cuttings Water loss due to transpiration.
Water uptake - no roots , - basal part of tracheas, tracheids are blocked, no water transport, - minimal water uptake through leaves, - more water uptake through basal part of cuttings.
Water deficit→ stomatal conductance reduced→ no CO2 uptake→reduced photosyntesis
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 58
How to control water loss of cuttings? Water loss depends on difference in vapour
pressure of leaf and environmental air.
Difference could be deminish - leaf temperature and vapour pressure of leaves - increased vapour content in environmental air, - combination of both factors.
Vapour pressure of leaves is function of - leaf temperature and - difference between leaf temperature and the leaf-air temperature difference (Δt).
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 59
Importance of solar radiation When solar radiation intensity is larger than 0,8 J
cm-2 min-1 (Klougart 1975) shading is required. Large fluctuation in solar radiation
in May 250 – 540 J cm-2
in Agust 250 – 2100 J cm-2 (Klougart 1975). Shading reduces insolation at 70-80%. Long wave radiation gets throug PE tent →plant
temperature is higher than under glass, but during the night the temperature decrease more.
White plastic foil reflects 40-60% of solar radiation.
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 60
Options in reducing water loss of leafy cuttings in propagation technology Using closed propagation units
(polythene tent, closed systems inside the glasshouse, polythene tent, shading, contact plastic cover, wet cover)
Intermittent mist (open and closed propagation units)
Fog system
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 61
Closed propagation units: advantages and shortcomings Simple and cheap (glass, polythene tent, etc.) Heat trap effect → increasing leaf – air vapor pressure
difference → water loss. Shading is required:
- PE-inner cover, modifyed PE foils (vinil-acetate, Al- or Mg-silicate added) long wave radiation in reflected - flies
Additional mist or fog systems could be installed. Contact foil cover: advantageous when radiation and
temperature is controlled, condeansation of vapour contributrs to wetting of leaves. Recommended for less sensitive leaves (evergreens – thick epidermis – danger of drying out is lower).
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 62
Double cover inside the polythene tent
Dr. Hrotkó Károly
Environmental
conditions and
rooting of
cuttings 63
Shading is required !
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 64
Intermittent mist: benefits and shortcomings Water film on leaves reduces leaf temperature → reduced
leaf vapour pressure – minimal difference in vapor pressure between leaves and air → reduced leaf transpiaration.
Intermittent mist reduces the air temperature due to evaporation → advective cooling of leaves.
High air vapour content (80-95% relative humidity) reduces the Δ RH.
Reduces the temperature in rooting zone – bottom heat is required.
Leaching of nutrients from leaves and cuttings. Applyed in closed propagation units.
(Environmental factors in open systems are less controllable, nowadays are not utilized in practice.)
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 65
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 66
Propagation unit with intermittent mist and shading
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 67
Application of intermittent mist and shading in PE tent and glasshouse
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 68
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 69
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 70
Fog systems High air relative humidity.
Fog systems spray at 40-60 bar pressure water drops of 15 μm size into air, which remain flotating.
Reduces leaching of nutrients.
No temperature decrease in rooting zone.
Larger costs in investment and maintenance .
Applicable for acclimatization of in-vitro plants also.
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 71
Propagation unit with fog system
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 72
Importance of temperature Optimum temperature at temperate zone plants 18-25
˚C, at tropical and subtropical plants 25-32 °C
Higher temperature at daytime (21-27 °C), lower at night (15 °C) .
Higher temperature increases the shoot growth in contrary root formation; by using bottom heat could be balanced.
At root growth higher roote zone temperature is recommended while for formation of root initials lower temperature is favourable.
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 73
Role of light in rooting of cuttings Rooting requires relative low solar radiation.
Cuttings of some herbaceous plants (Chrisanthemum, Pelargonium, Poinsettia) root better at increased solar radiation (116 Wm-2), optimum differrs by species (20-100 Wm-2).
Cuttings of some ornamental plants root better at long-day conditions.
Long day conditons are preferable for growth of rooted cuttings eg. Rododendrons (additional lighting in wintertime is favourable).
Red and fare-red wavelength is favourable for rooting (rooting is linked to phytochrom-system!).
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 74
Photosysnthetic activity of cuttings For rooting no highest photosysnthetic activity is
required, too high PAR increase the danger of drying out of cuttings.
After rooting intensive photosynthetic activity is required for growth of cuttings.
Citokinin formation of cuttings increase the stomatal conductance and the intensity of photosynthesis.
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 75
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Treatment Rooting % Cuttings’ weight (g)
Untreated 37,5 b 1,74 ab
IBA 60,4 cd 1,48 ab
IBA + Pentakeep V 81,3 e 2,53 c
IBA + Kelpak 47,9 bc 1,90 b
IBA + Wuxal Ascofol 68,8 de 2,01 b
Yeald Plus 66,7 de 1,94 b
Benziladenin 0,02% 6,3 a 1,29 a
Effect of treatments
on Prunus mahaleb ‘Bogdány’ cuttings (Szabó et al. 2011)
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 77
Benefits and shortcomings of different propagation systems in technology Working with cuttings placed on ground is difficult. Replanting, potting of rooted cuttings is not economical. Mist propagation when using high Fe and Mg containing
water cause stayning by salt – cuttings are not attractive. Bottom heat is required when using mist beacause of
temperature decrease in rooting zone. Nutrient leaching from cuttings could not be balanced by
spray with fertilizers. White (milk foil) cover reflects of 40-60% of radiation,
isothermal condition, minimal vapour condensation. Using propagatin trays nutrient sprays after rooting
improves the growth of cuttings.
Dr. Hrotkó Károly Environmental conditions and rooting of cuttings 78
Autovegetative propagation in nursery 79
Autovegetative propagation in nursery
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Autovegetative propagation in nursery
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Vegetatív szaporítási módok
Taking and preparation of cuttings - Timing: easy to root plants during winter dormancy, difficult to root species only in rooting optimum - taking and cutting preparation - hormonal treatment, wounding - using antitranspirants
Hardwood cuttings
Autovegetative propagation in nursery 84
Autovegetative propagation in nursery 86
Autovegetatív szaporítások
Autovegetative propagation in nursery 87
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taking of cuttings (date)
roo
tin
g (
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Fehér besztercei
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GF 8-1)
Polinom. (Sainte
Julien GF 655/2)
Optimal timing of plum hardwood cuttings
Autovegetative propagation in nursery 88
straight heel mallet
Cutting types and wounding
Polarity
Storage of cuttings - temporary storage at autumn planting - Cold storage (+ 2°C) - bottom heat → storage
Planting cuttings in open field in spring - optimal soil temperature (10-12 °C) - planting by machine or by hand - soil covering, black plastic soilc covers - mounding up
Taking care of cuttings during season Lifting specialities
Major steps in rooting technology of hardwood cuttings
Storage of hardwood cuttings
Autovegetative propagation in nursery
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Bottom heat treatment should be ceased
before root initials start grow!
Bottom heat treatment of hardwood cuttings
Autovegetative propagation in nursery 93
’St. Julien A’ hardwood cuttings in open ground conditions