asexual propagation. two types of reproduction in plants sexual reproduction –development of new...

Asexual Propagation

Two Types of Reproduction in Plants• Sexual Reproduction

– development of new plants by the process of meiosis and fertilization in the flower to produce a viable embryo in a seed

• Asexual Reproduction– The production of new plants by

any vegetative means not involving meiosis and the union of gametes

Advantages of Asexual (Vegetative)

Reproduction– Maintain clone– Uniform results– Faster (cut production time)– May be cheaper– “Custom Design” a plant– Can use it for experimental

purposes•Virus Indexing -Bud and graft to

diagnose plant diseases

Disadvantages of Vegetative Reproduction• Diseases

– Propagate disease with plant– (seeds occasionally spread disease also,

cruciferous seeds are dropped in boiling water to stop disease)

– Certified plants – use virus indexing or tissue culture to get disease free plants

• Costly– Sometimes more expensive vegetatively– e.g. tomatoes – easy by cuttings,

cheaper buy seed

Disadvantages of Vegetative reproduction• No Variation – no rearranging

genetics, no new cultivars– Couldn’t breed..

• Disease resistant plants• Plants that use less fertilizer• Insect resistance• No genetic variation• Plants with higher yields

Types of Vegetative Reproduction• Apomixis• Layering• Cuttings• Grafting• Tissue Culture• Specialized stems and

structures

Types of Vegetative Reproduction

Stigma surface

Pollen tube

Generative nuclei

Tube nucleus

Ovary wallChalazaAnitpodal cells

Two polar nucleiNucellusEggSynergid cellsIntegumentsMicropyleFuniculus

Embryo sac

• Apomixis– Vegetative

seed• Bluegrass• Citrus• onions

– Gen nuclei causes mitosis of cell membrane

– Clone of female

Types of Vegetative Reproduction• Layering

Types of Vegetative Reproduction• Layering

Air- Layering

Types of Vegetative Reproduction• Cuttings

– Stem cuttings• Herbaceous• Softwood• Deciduous hardwood• Narrow-leaved evergreen hardwood• Semi hardwood

– Whole leaf– Leaf sections– Leaf bud cuttings– Cane cuttings– Tip cuttings– Bulb leaf cuttings– Root cuttings

Grafting Tools and Terms• Stock• Scion• Interstock• Hand pruners• Grafting knife• Grafting wax• Budding rubbers

Grafting “Rules”• Close taxonomic relationship (family)

– Dif Genera only a few– Species (Plums onto Peaches)– Cultivars of species (almost always will

work)– Puzzles of incompatibility

• Pear on quince (sometimes)• Quince on pear never

• 2 parts secure• Protect from dessication• Polarity

Types of Grafting

• Grafting – joining parts of plants together to unite and grow as one– Budding – scion of one bud

• T-bud• Patch bud

– Grafting – scion of two or more buds• Side or stub graft• Side bark graft• Whip and tongue• Cleft graft• Approach graft• Bridge graft• Inarching• Top-working (changing cultivars)

Patch budding

Banana graftApple whip tongue grafting

Approach Graft – 2 methods

Whip and

Tongue Graft

Types of Vegetative Propagation

• Tissue Culture• Specialized Stems and Structures

– Divisions– Stolons– Rhizomes– Suckers– Crowns– Corms – Bulbs– Tubers– Tuberous roots

Tissue Culture/Micropopagation• Tissue culture is a process

where tiny plantlets are maintained on sterile artificial media containing nutrients.

• Totipotency describes the capacity of certain cells to regenerate a whole plant. Meristems are considered to be totipotent.

Tissue Culture/Micropopagation

• Advantages– Takes less room– quicker

• Method– Undifferentiated cells

(explants) placed on agar with nutrients and hormones under sterile conditions

– Callus tissue generates cells in globs like jello

– dividing callus tissue is influenced with growth hormones

– Can get millions from a single plant

Stem structure

Other forms of Stems

• Chief characteristics are nodes and internodes

• The following structures also have nodes and internodes and are therefore stems– Rhizome– Stolon– Corms– Bulb– tuber

Node

Internode

Corm

Cormels

Bulbs

Bulbils

Tuber

Sweet potato - YamStem or Root?

Root Types

• Fibrous• Tap roots• Adventitious roots

– Secondary roots– Aerial roots

Root Functions

• Absorb water and nutrients– autotrophic

• Anchorage• Storage• Propagation • Photosynthesis• Aerial roots help plant cling or

climb