Asexual Propagation

Various Types

• Cuttings

• Micropropagation

• Separation/Division

• Grafting

• Budding

• Layering

Micropropagation

Known as tissue culture• Place a piece of terminal shoot/leaf

buds in a agar or gel.

Newest approach in plant propagation

Separation/Division

Plants are removed from parent plants and planted to grow new plants.

Division – Plants are cut into sections, each capable of developing new plants.

Division

Different forms include• Rhizomes – Snake Plant

• Tubers - Potato

• Tuberous Roots – Dahlia, Sweet Potato

Cuttings

Many forms and approaches

• Softwood/Herbaceous

• Semi-hardwood – Shrubs, Woody Stemmed

• Hardwood - Trees

Herbaceous Cuttings

Succulent greenhouse plants can make numerous cuttings

from parent plantcuttings 2-6 inches long

Herbaceous Cuttings

remove bottom leavesroots will grow from the node

where leaves were attachedUse rooting hormonenot requiredspeeds rooting process

Herbaceous Cuttings

high humiditybottom heat helps speed rootingLeaf CuttingsAfrican VioletUse leaf and petiole

Herbaceous Cuttings

Leaf-bud cuttingscut bud and leaf from stemcut leaf to a smaller sizerequires less moisture

GROWTH STIMULANTS,

RETARDANTS AND ROOTING

HORMONES

Growth Regulating Substances

Called hormones: organic chemicals which act and interact to affect growth rate

Auxins: accelerate growth by stimulating cell enlargement

Gibberellins: stimulate growth in stem and leaf by cell elongation

Cytokinins: stimulate cell division (only works with auxins present)

Inhibitors: inhibit seed germination, stem elongation and hasten ripening of fruit.

Growth Hormones

Organic chemicals principally produced by actively growing plant tissue such as short tips and young leaves.

They move throughout the plant and can be found in many parts.

They react with one another.

Apical Dominance The terminal bud secrets chemicals which inhibit

or prevent growth of lateral buds. This causes the plant to grow tall and not send

out side branches. Seems to be a genetic program directing the

plant to grow above competing plants. Once the plant reaches flowering age, the

terminal bud becomes a flower bud and the chemicals are no longer secreted.

Pinching the terminal bud has the same effect and side branching occurs sooner.

Major Discoveries

Chemical and natural stimulants that cause plants to grow taller or faster

Chemical retardants that cause plants to grow slower

Hormones that cause plants to root faster Dwarfing rootstock for fruit trees

Chemical Stimulants

Enables plants to grow taller. Most common is gibberellic acid Gibberellic acid causes the stems of

plants to stretch out The nodes (the joints at which bulbs,

leaves and branches) are further apart

Natural Stimulants

Chemical known as alcohol Triacontanol Stimulation is brought about by

mulching with alfalfa hay or by watering plants with an alfalfa tea

Chemical Retardants Used to retard the growth of plants making them

shorter and more compact and therefore more attractive.

One of the newest applications for growth retardants is on lawns, a chemical called “Limit” is used new and it restricts grass growth for 6 to 8 weeks.

A new plant regulator called “Sumagic” reduces the height of plants by inhibiting production of the hormone Gibberellic acid. (which cause stems to elongate)

Rooting Hormones

When propagating plants from cuttings, it is very important that they root as quickly as possible

Indoleacetic acid (IAA) is a natural plant hormone that causes roots to form

Chemical hormones, indolebutyric acid (IBA) or naphaleneacetic acid (NAA) are the most common used today.

Rooting Hormones

Rooting hormones are either mixed with talc and used as powders or mixed with liquid and used as a wet dip

All rooting hormones should contain a fungicide.