Plant Propagation Test 3

Graft compatibility

The ability of two different plants, grafted together, to produce a successful union and to develop satisfactorily into one composite plant

Detached Scion Graftage—Apical Graftage

Type of graft used when a section of the shoot of the scion is removed & grafted to the apex or side of the rootstock. Many variations of apical graftage (scion is inserted into top of severed rootstock shoot).

Preformed roots

or latent root initials generally lie dormant until the stems are made into cuttings & placed under environmental conditions favorable for further development & emergence of the primordia as adventitious roots.

June budding

budding done from May to early June, which produces a smaller budded plant with a 1-year scion/1-year rootstock.

Budding

is a form of grafting in which the scion consists of a single bud and a small section of bark with or without the wood.

Budding

is a form of grafting, is three times more costly than cuttings and fourteen times more expensive than seedling propagation.

Formation of the Graft Union

1. Lining Up Vascular Cambiums of the Rootstock and Scion 2. Wounding Response 3. Callus Bridge Formation 4. Wound-Repair Xylem and Phloem: Differentiation of Vascular Cambium Across the Callus Bridge. 5. Production of Secondary Xylem and Phloem from the New Vascular Cambium in the Callus Bridge.

TWO PATTERNS OF ADVENTITIOUS ROOT FORMATION

-DIRECT ROOT FORMATION OF CELLS IN CLOSE PROXIMITY TO THE VASCULAR SYSTEM. -INDIRECT ROOT FORMATION, WHERE NONDIRECTED CELL DIVISIONS, INCLUDING CALLUS FORMATION, OCCUR FOR AN INTERIM PERIOD BEFORE CELLS DIVIDE IN AN ORAGANIZED PATTERN TO INITIATE ADV ROOT FORMATION.

Time of budding:

Spring Budding. June Budding. Summer Budding.

Shoot Organogenesis

Adventitious bud differentiation & subsequent adventitious shoot formation may also be obtained by direct organogenesis or via secondary organogenesis from disorganized callus.

ROOT CUTTINGS

Best results if root pieces are taken from young stock plants in late winter or early spring when roots are still supplied with stored carbohydrates but before new growth starts. Proximal end of the root piece should always be up, insert cutting vertically so that the top is at the soil level.

Seedling

Can be mass-produced relatively simply & economically. Viruses are transmitted from parent to progeny rare. Tend to have deeper rooted & more firmly anchored plants. May show genetic variation leading to variability in growth & performance of scion; selection of special mother tree (elite) seed. Uniformity can be controlled by managing production practices.

REASONS FOR GRAFTING AND BUDDING

Certain cultivars cannot be readily maintained or economically propagated by other asexual means. Combining different cultivars into a composite plant as scion, rootstock, & interstock. Changing cultivars of established plants. Repairing graftage for injuries. Disease indexing. Study of plant development & physiological processes.

The two most important types of budding fit woody ornamentals & fruit trees.

Chip budding and T-budding are the two most important types of budding for woody ornamentals and fruit trees.

Relationship of Stem Structure & Rooting Ability

Continuous sclerenchyma ring between phloem & cortex, exterior to the point of origin of adventitious roots, occurs as the stem matures. Sclereids occur in difficult to root species, while easy to root characterized by discontinuity or fewer cell layers of this sclerenchyma ring.

What are the factors involved in the care of cuttings during rooting?

Cutting Nutrition. Environmental Conditions. Sanitation and IPM. Weed Control. Herbicide Use in Propagation.

Explain cutting propagation

Cutting propagation utilizes a portion of stem, root, or leaf that is cut from the parent or stock plant and induced to form roots and shoots by chemical, mechanical, and/or environmental manipulation.

Cuttings

Cuttings are made from the vegetative portions of the plant, such as stems, modified stems (rhizomes, tubers, corms, and bulbs), leaves, or roots.

What types of plants are cuttings important for?

Cuttings are the most important means of propagating ornamental shrubs—deciduous species as well as the broad- and narrow-leaved types of evergreens.

Types of grafts can be categorized as:

Detached scion graftage. Approach graftage. Repair graftage of established trees.

Wound-Induced roots

Develop only after cutting is made, in response to wounding in preparing the cutting.

Bark grafting

Done in topworking of established plants. Rootstock must be in active stage of growth, so bark will slip; scion inserted between bark & wood of rootstock.

Effect of the Scion Cultivar on the Rootstock

Effect of the Scion on the Vigor and Development of the Rootstock.

History of grafting

Evidence that the art of grafting was known to the Chinese at least as early as 1560 BC. Aristotle & Theophrastus, 384-287 BC. The Renaissance period (AD 1350-1600) saw renewed interest in grafting practices. Early in the 18th Century, Stephen Hales, in his studies on the "circulation of sap" in plants.

Reasons for graft incompatibility:

External Symptoms of Incompatibility. Anatomical Flaws Leading to Incompatibility. Nontranslocatable (Localized) Incompatibility. Translocatable Incompatibility. Pathogen-Induced Incompatibility. Causes and Mechanisms of Incompatibility. Physiological and Biochemical Mechanisms. Modification of Cells and Tissue. Predicting Incompatible Combinations. Correcting Incompatible Combinations.

The stock plants and other sources from which the cutting material is obtained should be:

Free of disease and insect pests. True-to-name and type. In the proper physiological state so that cuttings root successfully.

Anatomical Origin of Wound-Induced Roots

Generally, the origin & development of de novo adventitious roots takes place next to & just outside the central core vascular tissue.

Repair graftage of established trees

Graft used in repairing or reinforcing injured or weak trees.

Types of stem cuttings:

Hardwood Cuttings: Deciduous Species. Hardwood Cuttings: Narrow-Leaved Evergreen Species. Semi-Hardwood Cuttings. Softwood Cuttings. Herbaceous Cuttings.

Factors that influence graft union success include:

Incompatibility. Plant species and type of graft. Environmental conditions during and following grafting. Growth activity of the rootstock. Polarity. The craftsmanship of grafting. Virus contamination, insects, and diseases. Plant growth regulators and graft union formation. Post-graftage—bud-forcing bethods.

What is layering?

Layering is a way of rooting cuttings in which adventitious roots are initiated on a stem while still attached to the plant.

Leaf cuttings

Leaf blade, or lf blade & petiole utilized in starting new plants. Adventitious buds, shoots, & roots form at base of leaf & develop into new plants. Only useful on limited number of species.

LEAF-BUD CUTTINGS

Leaf-blade, petiole, & short piece of the stem with the attached axillary bud; only adventitious roots need to form. Axillary bud at the nodal area provides the new shoot.

What are the reasons for layering plants?

Maintaining a Physical Attachment of Stem to the Mother Plant. Accumulation of Photosynthates and Hormones in the Rooting Area. Light Exclusion in the Rooting Zone. Invigoration and Rejuvenation. Seasonal Patterns.

Advantages to budding:

Makes very efficient use of scionwood, because only a single bud is needed to propagate a new tree. Makes good use of plant material in cases when scionwood of a particular clone is limited. May also result in a stronger union. Simplicity & speed of this technique.

Side grafting

Many types; scion is inserted into the side of the rootstock which is generally larger in diameter than the scion. Method has been proven useful for large-scale production, rootstock shoot generally removed after scion takes.

Cutting propagation is one of the most important means for clonal regeneration of many horticultural crops, such as:

Ornamentals. Fruits. Nuts. Vegetables.

Two types of callus formation:

Root Organogenesis. Shoot Organogenesis.

Root Organogenesis

Roots frequently emerge from callus, leading to the belief that callus formation is essential for rooting.

Root grafting

Rootstock seedling, rooted cutting, or layered plant is dug up, & roots used as rootstock of the plant.

Desirable rootstock characteristics:

Rootstock should have the desired characteristics of vigor, proper growth habit, and resistance to soilborne pests, as well as being easily propagated.

Layering procedures:

Simple layering. Compound layering. Serpentine layering. Air layering. Mound layering or stooling. Trench layering.

Effects of the Rootstock on the Scion Cultivar

Size and Growth Habit. Fruiting. Size, Quality, and Maturity of Fruit. Miscellaneous Effects of the Rootstock on the Scion Cultivar.

Stages of De Novo Adv Root Formation

Stage I - Dedifferentiation of specific differentiated cells. Stage II - Formation of root initials from certain cells near vascular bundles, or vascular tissue. Stage III - subsequent development of root initials into organized root primordia. Stage IV - growth & emergence of the root primordia outward through other stem tissue. Plus the formation of vascular tissue between the root primordia & the vascular tissue of the cutting.

18th century Grafting History

Steven Hales: Studies on the "circulation of sap" in plants; approach-grafted 3 trees, found that the center tree stayed alive even when severed from its roots. Duhamel: studied wound healing & uniting of woody grafts. Thouin: 1821, described 119 methods of grafting, discussed changes in growth habit resulting from grafting.

Approach graftage

The root system of the scion & shoot system of the rootstock are not removed until after successful graft union formation occurs. 2 self-sustaining, independent plants grafted together; may provide a mean of establishing a graft union between certain plants which are otherwise difficult to successfully graft. Should be done at times of year when growth is active & rapid healing of the graft union will take place.

For any successful grafting operation, producing a plant requires five important elements:

The rootstock and scion must be compatible. The vascular cambium of the scion must be placed in direct contact with that of the rootstock. The grafting operation must be done at a time when the rootstock and scion are in the proper physiological stage. All cut surfaces must be protected from desiccation. Proper care must be given to the grafts for a period of time after grafting.

Time to From Adventitious Roots

Time for root initials to develop after cuttings placed in the propagating beds varies widely. Once primordia are formed, there is a comparable time period between root primorida elongation (emergence) & maximum rooting in both easy & difficult to root species.

PLANT MODIFICATIONS RESULTING IN NATURAL LAYERING

Tip Layering. Runners. Stolons. Offsets. Suckers. Crown Division.

The rooting medium has four functions:

To hold the cutting in place during the rooting period. To provide moisture for the cutting. To permit exchange of air at the base of the cutting. To create a dark or opaque environment by reducing light penetration to the cutting base.

Equipment for Grafting

Tools and Accessories for Grafting. Grafting Machines. Grafting Automation/Robotics. Selection, Handling, and Storage of Scionwood.

Clonal

Vegetatively propagated by stool, layering, rooted cuttings, or microprop. Production of high numbers of such plants, upon which scion can be grafted or budded. Apomictic seed of citrus used for genetically uniform rootstock. Produce uniformity. Special characteristics such as disease resistance, size & growth habit of grafted plant, flowering & fruit development.

What are the different types of adventitious root formations?

Wound-Induced Roots. Time to Form Adventitious Roots. The Anatomical Origin of Wound-Induced Adventitious Roots. The Relationship of Stem Structure and Rooting Ability.

Root cuttings & leaf cuttings must...

must initiate both a new shoot system (from an adv bud) as well as new adventitious roots.

Adventitious roots can be of 2 types:

preformed roots & wound induced roots.

Propagation by stem & leaf-bud cuttings (single-eye cuttings) requires...

requires only that a new adventitious root system be formed, because a potential shoot system (bud) is already present.

De novo

roots that form "anew" (from scratch) from stem or leaf cells that experience a stimulus, such as wounding, to dedifferentiate into roots.

Rootstocks can be divided into 2 groups:

seedling & clonal.

Summer budding

sometimes referred to as fall budding, misnomer since this budding occurs from mid-July to early September, not in autumn; A 1-year scion/2-year rootstock is generally produced.

adventitious root formation

the primary regenerative process required in most cutting propagation.

Types of cuttings:

-Stem. -Leaf. -Leaf-bud. -Root.

Grafting

among the most expensive propagation techniques, surpassing even micropropagation.

Callus

an irregular mass of parenchyma cells in various stages of lignification that commonly develops at the basal end of a cutting placed under environmental conditions favorable for rooting.

Spring budding

budding that is done as soon as new seasonal growth occurs, in late March to early May depending on location; a 1 year scion/2-year rootstock is generally produced.

Graft failure

can be caused by anatomical mismatching, poor craftsmanship, adverse environmental conditions, disease, and graft incompatibility.

Dedifferentiate

capability of previously developed, differentiated cells to initiate cell divisions & form new meristematic growing points.