Asexual Propagation l Various Types Cuttings Micropropagation Separation/Division Grafting Budding Layering

Micropropagation l Known as tissue culture Place a piece of terminal shoot/leaf buds in a agar or gel. Newest approach in plant propagation

Separation/Division l 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 l Different forms include Rhizomes – Snake Plant Tubers - Potato Tuberous Roots – Dahlia, Sweet Potato

Cuttings l Many forms and approaches Softwood/Herbaceous Semi-hardwood – Shrubs, Woody Stemmed Hardwood - Trees

Herbaceous Cuttings l Succulent greenhouse plants l can make numerous cuttings from parent plant l cuttings 2-6 inches long

Herbaceous Cuttings l remove bottom leaves l roots will grow from the node where leaves were attached l Use rooting hormone l not required l speeds rooting process

Herbaceous Cuttings l high humidity l bottom heat helps speed rooting l Leaf Cuttings l African Violet l Use leaf and petiole

Herbaceous Cuttings l Leaf-bud cuttings l cut bud and leaf from stem l cut leaf to a smaller size l requires less moisture

GROWTH STIMULANTS, RETARDANTS AND ROOTING HORMONES

Growth Regulating Substances l Called hormones: organic chemicals which act and interact to affect growth rate l Auxins : accelerate growth by stimulating cell enlargement l Gibberellins : stimulate growth in stem and leaf by cell elongation l Cytokinins : stimulate cell division (only works with auxins present) l Inhibitors : inhibit seed germination, stem elongation and hasten ripening of fruit.

Growth Hormones l Organic chemicals principally produced by actively growing plant tissue such as short tips and young leaves. l They move throughout the plant and can be found in many parts. l They react with one another.

Apical Dominance l The terminal bud secrets chemicals which inhibit or prevent growth of lateral buds. l This causes the plant to grow tall and not send out side branches. l Seems to be a genetic program directing the plant to grow above competing plants. l Once the plant reaches flowering age, the terminal bud becomes a flower bud and the chemicals are no longer secreted. l Pinching the terminal bud has the same effect and side branching occurs sooner.

Major Discoveries l Chemical and natural stimulants that cause plants to grow taller or faster l Chemical retardants that cause plants to grow slower l Hormones that cause plants to root faster l Dwarfing rootstock for fruit trees

Chemical Stimulants l Enables plants to grow taller. l Most common is gibberellic acid l Gibberellic acid causes the stems of plants to stretch out l The nodes (the joints at which bulbs, leaves and branches) are further apart

Natural Stimulants l Chemical known as alcohol Triacontanol l Stimulation is brought about by mulching with alfalfa hay or by watering plants with an alfalfa tea

Chemical Retardants l Used to retard the growth of plants making them shorter and more compact and therefore more attractive. l 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. l 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 l When propagating plants from cuttings, it is very important that they root as quickly as possible l Indoleacetic acid (IAA) is a natural plant hormone that causes roots to form l Chemical hormones, indolebutyric acid (IBA) or naphaleneacetic acid (NAA) are the most common used today.

Rooting Hormones l Rooting hormones are either mixed with talc and used as powders or mixed with liquid and used as a wet dip l All rooting hormones should contain a fungicide.