Propagation FINAL

How is light measured, and how is light manipulated in plant propagation?

The lux (symbol: lx) is the SI derived unit of illuminance, measuring luminous flux per unit area. It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface.

Understanding grafting compatibility among varieties, species, genus, and family.

The farther towards order, the less compatible.

Variegation is the appearance of differently colored zone in the leaves, and sometimes the stems of plants. Not all variegated plants are chimeras!

Variegation is the appearance of differently colored zone in the leaves, and sometimes the stems of plants. Not all variegated plants are chimeras!

Define grafting.

is the art of joining two pieces of living plant tissue together in such a manner that they will unite and subsequently grow and develop as one composite plant.

Be able to draw the different types of layering we discussed in class.

• Simple layering • Compound layering • Serpentine layering • Air layering • Mound/stool layering • Trench layering • Drop layering

Know the rejuvenation and etiolation of stock plant for maximize cutting propagation.

(a) Etiolation frames in place over stock plant hedges (b) Improved tooting following etiolation Cuttings from nonetiolated stock plants have poor rooting. Etiolation /iːtiəˈleɪʃən/ is a process in flowering plants grown in the partial or complete absence of light. It is characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow color (chlorosis). The Rhizocaline effect of growth substances translocated from the juvenile (easy -to -root) leaf to improve rooting in the mature petiole (difficult-to-root) of reciprocally-grafted, English ivy.

How are propagation soil sanitized?

(a) Fumigation tank and (b) a tractor to apply the chemical and cover the field with a poly tarp. (c) Chemical fumigant injected into propagation medium covered with poly. Chemical fumigants are extremely toxic; during soil treatment, it is important to use warning signs and restrict the movement of personnel.

Know the various media/substrate used for propagation.

(a) peat-lite soilless mix (b) sand (c) bark mix (d) perlite

Know the different types of seed testing.

- Germination testing - Tetrazolium testing - Purity testing - Vigor testing - X-ray

What are the factors influencing grafting success?

- 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 methods

What are four essential components of a tissue culture medium?

- Inorganic nutrients (fertilizer) - Organic compounds (vitamins and sugar) - Growth regulators (hormones) - Support (agar)

Discuss the fundamental activities involved in agriculture.

-Plant selection -Plant propagation -Crop production -Crop handling and storage -Food technology

What are the three features of micropropagation?

-Start with small explant. - Aseptic culturing environment. - Media containing nutrients and plant hormones.

Alignment of what kind of tissue is critical for grafting to success?

Cambium tissue of scion and root stock

Mound layering is often used on what kind of plants.

Numerous fruit tree rootstocks, especially apple, are propagated by mound layering.

What are orthotropic cuttings?

Orthotropic growth •upright growth habit •cuttings from an upright terminal branch Growing vertically, either upwards or downwards.

Why is agar used in tissue culture?

An agar plate is a Petri dish that contains agar as a solid growth medium plus nutrients, used to culture microorganisms.

Understand the stability of chimeras.

Periclinal Chimeras are the most stable type.

Know the three agricultural revolutions.

1. Agriculture Revolution 8000 2. Scientific Agriculture 1800 3. Green Revolution 1964

Know the different types of seed dormancy.

1. Physical Dormancy 2. Physiological Dormancy

What is the F1 and F2 offspring from a cross between homozygous parents with a single trait?

3:1 segregation

Know the main phases of a plant.

Annuals - Herbaceous (non woody)- Complete life cycle in one season (seed -seed) Biennials - Herbaceous plants Ex. Onions, beets - Require two growing seasons: veg growth in 1st season, Dormant during winter, reproductive growth in 2nd season Perennials - Either herbaceous or woody - Herbaceous perennials - shoots and roots can stay alive indefinitely - Shoot system may be killed by frosts or other environmental factors - Shoot growth resumes from dormant buds at the crown of the plant Phase I: Seed germination Phase II: Juvenile (Vegetative) growth Leaves, stems, and roots Phase III: Adult (Reproductive) growth flowers, fruits, and seeds Phase IV: Senescence and death

What is air layering?

A form of layering in which the branch is potted or wrapped in a moist growing medium to promote root growth. Plants with large or mature stems - Don't easily bend - Do not sucker proficiently (a) A girdling cut is made in the stem to be layered. (b) Treat with auxin (optional) and wrap with moist sphagnum moss. (c) Seal with a poly bag. (d) Once rooting occurs the layered stem can be cut from the mother plant.

What are mallet cuttings?

A hardwood cutting of the current season's growth with a heel of the previous season's growth. A cutting consisting of a segment of the current season's growth with a leaf, axillary bud, and a small section of the stem used in the propagation of various plants.

What is a chimera?

A plant with two or more genetically dissimilar tissues growing side by side: some mutations genetically change only a portion rather than the entire shoot.

What is layering?

A propagation method that encourages adventitious root formation on stems remaining attached to parent plant. The rooted stem (layer) is then detached, transplanted, and become a separate plant on its own roots.

Know the structure of a seed.

A seed is consists of an embryo, a food supply (usually endosperm or cotyledon) and a protective covering (seed coat or pericarp). Intact seed on the left and half seed on the right exposing the embryo.

What is an advantage and disadvantage of air layering?

Advantage- This technique results in a good-sized plant in a matter of weeks instead of months or years. There is a minimum of disturbance and no adverse effect to the mother plant. During propagation, both the mother plant and the new plant continue to develop. Disadvantage- This method is laborious and therefore expensive. Only a small number of layers can be produced from a parent plant than when the same plant is used as source of cuttings, buds, or scions.

What are the advantages and disadvantages of leaf cuttings?

Advantages Leaf cuttings can have new plants regenerate from a) petiole or the cut surface of b) leaf blade. Very little expertise needed •Number of plants is determined by cutting •Separated from the parent plant at the petiole •Leaf can be subdivided into 3-5 cm squares containing a portion of the vein. Disadvantages Plants vary regarding adventitious root and shoot formation - Must have both to be successful •Rubber plant only grows roots •Chimeral plants will not propagate with the desired appearance (may have albinism).

What are the advantages and disadvantages of plant tissue culture?

Advantages- •Produce many plants that are clones of each other. •Many more plants can be produced in a smaller area with less mother stock. •Produce disease-free plants by eliminating pathogens. •Used to maintain germplasm: useful in multiplying plants which produce few or no seeds, or when plants are sterile or seeds can't be stored. •Produce rooted plantlets ready for growth, saving time for the growers when seeds or cuttings are slow. •It is the only viable method of regenerating genetically modifi ed cells. Disadvantages- •It is very expensive (lab + traditional propagation facilities + specialized labor). •Some plants are very hard to disinfest. •Not all plants can be successfully cultured because the proper media is not yet known or the plants produce chemicals that affect growth. •Sometimes plants are not true to type, depending on the type of explant materials used. •Floods market with genetically identical plants decreasing potential genetic diversity.

What is the primary regenerative process required in cutting propagation?

Adventitious root formation

What is an adventitious root?

Adventitious roots are plant roots that form from any non-root tissue and are produced both during normal development and in response to stress conditions, such as flooding, nutrient deprivation, and wounding.

Know the five main plant hormones and their commercial use in plant propagation.

Auxin- a plant hormone that causes the elongation of cells in shoots and is involved in regulating plant growth. Gibberellin- any of a group of plant hormones that stimulate stem elongation, germination, and flowering. Cytokinin- promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in cell growth and differentiation, but also affect apical dominance, axillary bud growth, and leaf senescence. Ethylene- influences diverse processes in plant growth, development, and stress responses throughout the plant life cycle. Responses to ethylene, such as fruit ripening, are significant to agriculture. Abscisic Acid- a plant hormone that promotes leaf detachment, induces seed and bud dormancy and inhibits germination.

Know the plant hormone used for cutting propagation. What are the functions of cytokinin and auxin in the formation of roots and shoots?

Auxins can enhance rooting but are not required in easy-to-root plants such as chrysanthemum. Auxins are needed to enhance rooting in moderately ready-to-root plants such as camellia. In difficult-to-root (recalcitrant) plants such as paw paw (Asimina), auxin has little effect on rooting. IBA (Indole-3-butyric acid) is a plant hormone belonging to the auxin family and assists in initiating root formation; the in vitro process is called micropropagation. Aside from accelerating root formation, it is used on various crops to stimulate flower development and the growth of fruits. Cytokinin Adventitious Bud and Shoot Formation in leaf and root cuttings Used in tissue culture systems in Stage II Shoot Proliferation ð High Cytokinin : Low Auxin ratio stimulates adventitious bud formation & overcomes apical dominance

What are chip budding and T-budding?

Chip budding is a grafting technique. A chip of wood containing a bud is cut out of scion with desirable properties. A similarly shaped chip is cut out of the rootstock, and the scion bud is placed in the cut, in such a way that the cambium layers match. T budding or shield budding is a special grafting technique in which the scion piece is reduced to a single bud. As with other techniques of asexual propagation, the resulting plants are clones (genetically identical plants reproduced from one individual entirely by vegetative means).

What are the major environmental factors that are important for successful stem cutting propagation?

Cutting position (whether cutting occurs above or below a node, as well as the relative proximity of the cut to the node) Length of cutting (including how many nodes remain on the cutting) Growth medium (whether left in the soil, water, potting mix, compost, or open-air) The use and concentration of growth hormones (e.g. IAA, IBA, and NAA promote the formation of adventitious roots) Temperature conditions (most cuttings grow optimally at temperatures common to spring and summer) Availability of water (either in the form of groundwater or humidity) Other environmental conditions (including pH of the soil and light exposure)

Know the binomial name for plants.

Each plant has a two-word—binomial—Latin name, which is international, and understood universally. - The first word refers to the genus; the second refers to species. - Genus: capitalized, italicized; species: lower case, italicized

Define explants.

Explants - used to regenerate new shoot systems that can be separated for rooting and growing into full-size plants. •Different parts of the plant can be used (seed, shoot-tip, poll en, anther, petal, leaf, meristem, root, etc.) •Materials must be surface sterilized to prevent fungal and bacterial contamination before placing on growth media. •Vary in results based on rate of growth, age of plant, and disinfestation success

Know the forms of genetic transformation.

Flower Dip Biolistics

What are the possible contaminations of plant tissue culture?

Fungi, bacteria, or viral organisms. • Contaminations grow much faster than most plant material. • Typical (a) fungal or (b) yeast microbial growth in contaminated tissue cultures and (c) internal bacterial contamination.

Mericlinal Chimeras

Genetically different tissue occurs in the part of one meristem layer •Common type of chimera •Central cell zone in one layer of meristem mutates •Division of that central cell forms a streak of mutant tissue extending the length of the shoot Normal or mutated cells do not extend through all layers within the bud or meristem. Usually one genotype (whether green or white) occupies a small portion of the meristem's outer layers

Know the terms "genus" "species" "botanical variety", and "cultivar".

Genus and species: Cercis canadensis L. Subspecies: Cercis canadensis subsp. Texensis Botanical variety: Cercis canadensis var. alba Cultivar: Cercis canadensis "Forest Pansy"

What are some of the more popular covering materials for propagation houses?

Glass Polyethylene covered high tunnel Polycarbonate sidewalls with a polyethylene cover Fiberglass sidewalls with a polyethylene cover

Discuss the advantages and disadvantages of different types of plant propagation structures.

Gutter-connected propagation greenhouses. (a) The basic types of gutter-connected greenhouses: bow or truss. Bows are less expensive, but offer less structural strength. Trusses make for a stronger house, while giving the ability to hang plants and equipment. (b) Non—load-carrying bow propagation house. (c) Load-bearing, gutter-connected truss house.

Know when these types of cutting are usually taken: hardwood, narrow leaf evergreens, semi-hardwood, and herbaceous cuttings.

Hardwood- Previous season's growth -Late fall to early spring -taken from midpoint of stem -15-30 cm (6 -12 in) in length -Diameter equal to or greater than a pencil -Contain at least 3 vegetative buds -Direct stick into raised beds -Examples are figs, roses, mulberry, pomegranates, grapes Narrow-leaf evergreens -Late fall to late winter •Many take several months to root •10-20 cm (4-8 in) in length •Less than pencil thickness •Bottom Branches removed •May be: -Tip cuttings -Heel cuttings -Mallet cuttings Semi-hardwood cutting -Late spring to late summer •Wood matured, but not woody •8 to 16 cm (3-6 in) •Basal thickness will vary •Lower 1/3 of leaves are removed •Large leaves can be cut back -Ex. Holly, boxwood, citrus, olive, evergreen Rhododendron,etc. Softwood Cuttings -Tip cuttings from new growth •Spring to early summer •7.5-12.5 cm (3-5 inch) •Same procedure as semi -hardwood except: -Flower buds should be removed as they appear -Terminal growth should be removed Herbaceous -Can be taken throughout the year •8-13 cm (3-5 in) •Same procedures as Semi-hardwood

What are heel cuttings?

Heel cuttings are made using side shoots taken off of woody stems that are at least 2 years old and contain a piece of the main wood stem at the base. Heel cuttings are often used to propagate plants that are otherwise fairly difficult to root.

How can humidity affect rooting cuttings? (which environmental condition is better, high humidity or low humidity?)

Humidity control: minimizing transpirational water loss from cutting Polyethylene-covered beds used to maintain high humidity during rooting.

Know the scientists who contributed to American Horticulture and the Green Revolution.

Liberty Hyde Bailey is considered the Father of American Horticulture Malpighi was a keen observer of plants, he wrote Anatome Plantarum, 1675 The Wardian case was invented by N. B. Ward in the early 19th Century to use when transporting plants over long ocean voyages. The first established nursery in the United States was begun in New York in 1730 by William Prince.

Compare the different methods of irrigation used in greenhouse.

Micro-irrigation 1. Drip-tube irrigation 2. Drip-tube emitter 3. Drip stake emitter system Microsprinkler irrigation Subirrigation 1. Ebb and floor system 2. Capillary mat system

Compare and contrast mitosis and meiosis, and discuss how they function during sexual and asexual (vegetative) propagation.

Mitosis produces two diploid (2n) somatic cells that are genetically identical to each other and the original parent cell, whereas meiosis produces four haploid (n) gametes that are genetically unique from each other and the original parent (germ) cell.

Preference of non-flowering versus flowering plant as stock plant.

Non-flowering.

What are the reasons for grafting?

Perpetuating clones desired for their fruiting, flowering, or growth characteristics that cannot be readily maintained or economically propagated by other asexual means. Combining different cultivars into a composite plant as scion, rootstock, and interstock—each part providing a special characteristic. - Obtaining the benefits of certain scions- Obtaining the benefits of certain rootstocks- Obtaining the benefits of certain interstocks (Double-Working) Repairs for injuries Study of plant developmental and physiological processes

How are the seeds treated to break dormancy?

Physical Dormancy- Scarification: Process of weakening or removing seed coat -Concentrated sulfuric acid -Sandpaper -Files -Hot water Physiological Dormancy- Stratification: mimic this winter effect by placing seeds in a moist environment in the refrigerator.

What is the importance of polarity in grafting? What happens if polarity of the scion is reversed?

Plant polarity refers to the asymmetric distribution of cellular components along a particular axis within a cell, and is essential for processes such as intercellular communication, cell division, cell morphogenesis and differentiation.

What special container is used for tree production?

Pot-in-pot

What role do plant hormones play in tissue culture?

Primarily used as growth regulators. • Auxins: cell enlargement and root growth (IAA, IBA, NAA) • Cytokinins: cell division and shoot initiation (BA, Kinetin, 2i P) • Gibberellins: cell enlargement and stem elongation (GA3) • Used at very low concentrations (0.001 - 10 μM) but yield dramatic results.

What is seed priming and what is the advantage?

Priming -Seeds hydrated to allow germination to begin -Germination process stopped before radicle emergence -Seed can be immediately planted or redried -Germination rate and uniformity are enhance Seed priming is a process of regulating the germination process by managing the temperature and seed moisture content, the seed is taken through the first biochemical processes within the initial stages of germination. Seed priming improves stand establishment, crop growth, and yield under optimal conditions. as well as under suboptimal conditions, such as salinity, drought, and temperature extremes.

What is rootstock, interstock, scion, stion, graft union, callus, callus bridge, etc.?

Rootstock- the plant that receives the fusion and has an established root system. Interstock- a piece inserted between scion and stock in grafting (as to allow the union of incompatible varieties or to induce dwarfing) Scion- a detached living portion of a plant (such as a bud or shoot) joined to a stock in grafting and usually supplying solely aerial parts to a graft. Stion- a combination of stock and scion. Graft Union- the anatomy which is formed when grafting a rootstock to a scion. Callus Bridge

Sectorial Chimeras

Similar to mericlinal •Except mutation occurs in the part of each meristematic layer •Results in a wedge of mutated tissue extending from axis to epidermis •Often occurs in embryonic tissues before meristem layering has developed -mutated cells extend through all cell layers, but only in a sector of the stem -rare in plants with layered meristems -unstable and tends to revert to periclinal or mericlinal or loss of chimera Sectorial chimeras result from mutations that affect sections of the apical meristem, the altered genotype extending through all the cell layers. This chimeral type is unstable and can give rise to shoots and leaves which are not chimeras.

What are the four main stages of plant tissue culture?

Stage 0 -Donor plant selection Stage I -Initiation or Establishment Stage II -Multiplication (shoot development) Stage III -Rooting Stage IV-Acclimatization (Hardening Off)

What are the three stages of adventitious root formation after taking a cutting?

Stage I - Dedifferentiation. Stage II - Root initial formation. Stage III - Root primordia formation. Stage IV - Root primordia elongation.

Know the rejuvenation and etiolation of stock plant for maximize cutting propagation.

Stock plant etiolation is a technique which involves excluding light during new shoot growth. Stem banding during stem development is an additional stock plant treatment which excludes light from that section of stem which will become the cutting base.

Periclinal Chimeras

The most stable form of chimera •All central zone cells in a single layer are mutated •"hand in glove" chimera: cells of one genotype completely surround another. The phenotype of the glove can mask the phenotype of the hand. A mutation produces a periclinal chimera if the affected cell is positioned near the apical dome so that the cells produced by subsequent divisions form an entire layer of the mutated type. The resulting meristem contains one layer which is genetically different from the remainder of the meristem.

What are the good characteristics of a substrate for stem cutting propagation?

The rooting substrate should retain moisture but remain well-drained. Flats that hold containers should have open bottoms to allow drainage from the excess mist. Various rooting media used by propagators (a) Sand (b) Bark (c) Peat -perlite mix (d) Perlite (e) Coconut coir (f) Pumice (g) Oasis foam block (h and i) Stabilized peat (j) Peat -perlite in a paper sleeve.

What are plagiotropic cuttings?

The situation where the vegetative propagule does not assume a normal tree form but continues to grow like a branch. When the scion or propagule grows in the same branchlike way, it is called plagiotropic growth. •lateral growth habit •cuttings from a lateral branch

Know the phases of seed germination and the events in each phase.

There are three phases to germination that can be described by the seeds increase in fresh weight (water uptake). These include the imbibition, lag, and radicle protrusion phases. Phase 1: Rapid uptake of water in response to matric forces of the seed. Phase 2: Membrane reorganization Enzyme activation RNA and protein synthesis Breakdown and transport of stored materials Phase 3: Radicle emergence due to cell elongation, embryonic shoot emergence, and seedling growth.

What kinds of containers are used for prevention of root circling? Why root circling is not desired in propagation?

Tiered or ridged containers Plastic (Rootainer) container made of preformed, hinged sheets for propagating seedling liners. Slits in the container side wall air prune circling roots Circling roots can mean unstable trees. Roots that circle next to or near the trunk were associated with numerous fallen trees.

What are tip cuttings?

Tip cuttings, which include the apex or plant tip and a small portion of the stem.

What are the major environmental factors that are important for successful stem cutting propagation?

Various rooting media used by propagators (a) Sand (b) Bark (c) Peat (d) Perlite (e) Coconut coir (f) Pumice (g) Oasis foam block(h and i) Stabilized peat (j) Peat The rooting substrate should retain moisture but remain well-drained. Flats that hold containers should have open bottoms to allow drainage from the excess mist. The importance of ergonomics and the efficiency of movement (a) Poor ergonomics with uncomfortable back posture. (b) Good ergonomics with correct posture, close proximity of materials and the economy of movement. (c) A two-person trolley where workers lay on pads to stick cuttings in-ground beds. (d) Ultimate efficiency with propagators "floating" above the containers sitting in a trellis system for direct sticking in a flood floor system.

Know what the vapor pressure deficit (VPD) is.

Water loss from cuttings during mist propagation is the difference of the vapor pressure between the leaf and the surrounding environment. This is vapor pressure deficit (VPD). For VPD models, sensors send data to a computer that calculates the VPD for the greenhouse environment. Crop models use VPD to estimate water loss from cuttings to initiate misting.

Understand the uses of whip grafting, cleft grafting, wedge grafting, bridge grafting, approach grafting, double working.

Whip Grafting- In whip and tongue grafting this is done when corresponding cuts through rootstock and scion material are joined end to end and then bound. The interlocking 'tongues' add structural support to the join as the cambium layers heal and fuse together, as well as giving a larger surface area of cambial contact. Cleft Grafting - a grafting technique that allows the union of a rootstock limb that is much larger in size than the scion piece. Wedge Grafting - cleft grafting is a method of propagating new limbs on plants such as fruit trees or bushes by removing a healthy branch, known as a scion, and physically connecting it to the stock of another tree at the desired location. Bridge Graft - is used to supplying nutrients to the rootstock of a woody perennial when the bark, and therefore the conductive tissues, have been removed from part of the trunk. Approach Grafting - It happens naturally in the wild when two branches rub against each other and eventually seal together. In the garden or greenhouse, you use it to join one whole living plant to another. Double Working - This involves placing an interstock between the scion and the rootstock. This may be done in certain fruit tree grafts where the scion and rootstock are incompatible, but the interstock is compatible with both the scion and rootstock.

What are the plants modifications resulting natural layering?

• Stolons Stolons are stems that grow horizontally above ground • Runners Runners are a specialized type of stolon that arises from the axil of a leaf at the crown. New plants arise at the tip as daughter plants. • Rhizomes Rhizomes are underground stems that grow horizontally.

Know the various methods used for leaf cutting (how you prepare the leaves).

•Perlite is a medium. Moistened vermiculite or moistened soilless media can be substituted for perlite, but the water holding capacity of either of these is significantly greater than that of perlite and may lead to a greater loss of leaves to disease unless the watering schedule is closely monitored. •Exogenous hormones are not usually used with leaf cuttings. The most reliable method for producing new plantlets from leaf cuttings is to use the entire leaf with the petiole still attached. Far more species have the ability to form both roots and shoot adventitiously from petiole tissue than from leaf blades or vein tissues.