METHODS OF ASEXUAL PROPAGATION CUTTINGS LAYERING/CIRCUMPOSING GRAFTING BUDDING

Methods of Asexual Propagation CUTTINGS

CUTTINGS Cuttings – pieces of vegetative material from any of the three primary plant organs – root, leaf and stem used to produce a new plant. Types 1. stem tip (terminal) cuttings 2. stem cuttings – taken from soft-wood, hard wood and semi-hard wood 3. Leaf cuttings – leaf vein, leaf bud and petiole 4. Root Cuttings

Biology of Adventitious Root Formation (Cutting) Propagation by stem, leaf, shoot tip and root cuttings require only new adventitious root system to be formed. This is dependent on the plant cells to dedifferentiate. That is the capability of the cell to initiate a new meristematic growing point.

Biology of Cuttings Roots of cuttings are wound-induced Roots are formed de novo The root regeneration process includes three steps: 1. The outer injured cells die, the wound is sealed with suberin and the xylem plugs with a gum

Root Generation Process 2. Livings cells divide after a few days and a layer of parenchyma cells (callus) forms a wound periderm 3. Certain cells in the vicinity of vascular cambium and phloem begin to divide and initiate de novo adventitious roots

Cross-Section of a Mature Stem

Biology 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)

Stem Structure and Rooting

Biology of Propagation by Cuttings Leaf Cutting Limiting Factor in Leaf Cutting Propagation is the Formation of adventitious buds Not Adventitious roots. Origin of new shoots and roots from: Preformed 1◦ meristems Wound induced 2 ◦ meristem

Biology of Propagation by Cuttings Developmental process of rooting has two Stages: Root initiation i) auxin-active: auxin is required for root formation ii) auxin-inactive: auxin not required for roots 2. Root elongation – auxin not required

High auxin/low cytokinin ratio favours adventitious rooting Low auxin/high cytokinin ratio favours adventitious buds/shoots Difficult to root plants often have high cytokinin levels

Factors Affecting Regeneration of Plants From Cuttings Management of stock plants to maximize cuttings. - Selection and maintenance of source material - Manipulating the environmental conditions and physiological status

Maintenance of Stock Plants - Maintain stock plant in juvenile/transition phase - Reversal from the mature to juvenile/transition phase - Re-establish high rooting potential - < 50 % rooting undesirable

Rejuvenation of stock Plant Ease of adventitious root formation declines with age of parent stock Transition from the Juvenile to mature stage – phase change or ontogenetic aging

Select a Healthy Parent Stock

Simple Cutting Procedure   If the stem has large leaves, cut the two largest ones in half. This means the cutting will lose less moisture from its leaves, allowing it to put more energy into forming roots.

Types of Hard Wood Cutting Straight Mallet Heel

Plant Produce by Cutting

The Biology of Cuttings

Minimum requirements for Cuttings Plant factors; 1. nutritional status of the plant 2. Hormone level 3. Juvenility 4. Position of the plant part

Minimum requirement Environmental factors; Darkness Light Temperature Moisture Time of day and year cutting is taken sanitation

Layering/Circumposing

Layering/Circumposing Describes as modified cutting – roots are generated on the stem or root of a plant before is completely cut away from the parent plant The newly rooted plant will survive independently of the mother plant.

Biology of Layering Accumulation of photosynthates and hormones in the rooting area are important to the success of root during layering Light exclusion Phloem interruption – breaks the flow of food from the upper stem to the girdled portion Girdling reduces water conductivity

Types of layering Natural layering – tip, runners, suckers, crowns. Simple layering – air layering, trench layering, mound layering, compound layering.

Simple layering . can be accomplished by bending a low growing, flexible stem to the ground

Tip Layering

Compound (serpentine) Layering

Mound Layering

Air-Layering

Layering

Minimum requirement - layering An appropriate rooting medium An appropriate material for holding the medium Adequate moisture Healthy plant source

Grafting

Grafting Parts of two different plants are joined so that they continue their growth as one plant. To accomplish this; one of the two plants serves as the bottom (in contact with soil) – rootstock The other serves as the top part – scion. The scion is being propagated and the only one allowed to grow.

Strategy in grafting Align tissues so that the vascular transport is restored between the two parts (scion and stock). Healing starts with the production of callus (undifferentiated cells). This occurs in the cambium region of the two parts. Followed by further differentiation of cells to form vascular tissue, completing the repair and allows vascular transport.

Strategy in Grafting Correct polarity is important to the success of grafting – proximal end of the scion should be inserted into the distal end of the rootstock Cell to cell recognition must occur as part of the adhesion process

The wound response is followed by the dissolution of the necrotic layer. There is direct cellular contact of plasmodesmata in the callus bridge that connects the grafting partners

Uses of grafting technique To propagate plants difficult to produce from cuttings. Provide disease resistance to a susceptible but desirable cultivar. To rapidly increase the number of a desirable cultivar. To change plant size and vigour

Uses of Grafting technique To repair damaged plant parts To change plant form Virus indexing

Types of Grafting Detached- scion grafting; - whip and tongue grafting - cleft (wedge and saddle) grafting - bark grafting Approach grafting Side grafting

Types of grafting Bridge grafting inarching

Saddle graft

Side veneer graft

Requirement for success Plant conditions 1. Compatibility 2. Diameter of the parts 3. physiological state 4. alignment of tissues Environment Operator

Flow chart of Grafting

Budding

Budding A form of grafting in which the scion consists of a single vegetative bud. The difference between budding and grafting is that bud uses a single bud as the scion, whereas grafting uses pieces of planting material consisting of several buds.

Types of budding T – budding Patch budding Chip budding

Removing the bark shield with the bud attached.

Bark shield with bud inserted into T cut.

Wrapped bud

Minimum requirement Actively growing rootstock (i.e. in spring, late summer or fall) Some of the factors in grafting.

Step 1 and 2

Step 3 and 4

Step 5 and 6

Step 7

Step 8

Reasons for Budding Change varieties or cultivars Optimize cross-pollination and pollination Take advantage of particular rootstocks Perpetuate clones Produce certain plant forms

In Class Assignment Read up on the types of each propagation technique (eg.) Types of budding, layerng etc. Read up on Propagule, Parthenocarpy Apomixis, chimeras, mutation, virus indexing

Support Site www.uvm.edu?~mstarret/plantprop/chapter9.pps - United States.

Reference Acquaah, G. (2009). Horticulture: principles and practices 4th ed. Hartman, H., etal. (1979). Plant Propagation: principles and practices 6th ed.

THE END Courtesy: L. Clarke, and M.Gager, CASE