植物繁殖（英文版）完整版

Plant

propagation•

Aims

and

purposes

of

session:–

To

outline

the

methods

of

propagating

plants

–

To

set

out

the

principles

of

seed

dormancy

andhow

to

overcome

it–

To

outline

the

principles

of

asexual

propagation

and

the

methods

used–

To

prepare

students

for

a

practical

session

on

propagationPlant

Propagation•

The

principles

of

plant

propagation1.

Totipotency

–

the

capability

of

a

single

cell

to

develop

into

a

full

plant

–

tissue

culturea.

Highly

specialised

skills

and

equipment2.

Sexual

reproduction

by

far

the

most

common

way

for

plants

to

reproduce

themselves

–

seeda.

Skills,

experience

and

some

specific

equipment

3.

Asexual

reproduction

occurs

naturally

–

but

othervegetative

techniques

developeda.

Skills,

experience

and

some

specific

equipmentMicro

propagation

–

totipotency•

Propagation

of

plants

from

very

small

portions

of

tissue

(tissue

culture)•

Grown

in

vitro

(under

glass)

•

Must

have

sterile

equipmentand

environment•

Work

done

in

a

laminar

flow

cabinet

passing

filtered

airacrosswork

place•

Grown

on

specially

formulated

gelatinous

or

liquid

mediumMicro

propagation•

Small

pieces

of

tissue

from

virus

free

shoottips•

Axillary

buds

stimulatedby

plant

growthregulators

in

growingmedium

gives

multiple-shoot

plantlets•

Plantlets

divided

andtransferred

to

freshgrowing

mediumMeconopsis

nepalensis

seedheadand

seedSeed

propagation•

Dormancya.

Survival

protectionmechanismb.

In

nature,

seed

dormancy

can

be

programmed

to

last

a

few

months

to

several

yearsc.

Different

strategiesrequired

to

breakdormancy

for

differentspeciesSeed

propagationCotoneaster

fruits

–

bird

dispersed

Taraxacum

–

wind

dispersedSeed

propagation•

Dormancy

–protected

by:1.

Chemical

inhibitors

present

in

the

seed2.

Hardened

seed

coatings3.

Requirement

for

specific

external

influences

–

e.g

extreme

heat

or

a

forest

fire•

Breaking

dormancy:

getting

moisture

inside

the

seed

coating1.

Warm

stratification

–

exposing

the

seed

to

warmth.

Artificial

heat

can

speed

up

germination

to

just

a

few

days

(seeds

which

are

designed

to

germinated

with

a

few

weeks

or

months

of

maturing

–

e.g.

annuals,

vegetables),

or

a

few

months

for

those

which

would

otherwise

take

a

year

or

more

to

germinate.

In

the

latter

case,

a

period

of

cold

stratification

may

be

required

as

well.2.

Cold

stratification–

this

involves

exposingthe

seed

to

a

period

of

cold,

such

as

in

a

refrigerator

to

mimic

a

winter

’s

weather.3.

Scarification

–

the

piercing

of

the

hard

seed

shell

by

abrasion

or

nicking

with

a

knife

to

allow

water

to

enter.

Sometimes

preceded

by

soaking

the

seed

for

up

to

24

hours

to

soften

the

coating.Broad

BeanSeed

propagation•

Germinationrequirements:a.

Oxygenb.

Waterc.

temperatureSeed

propagation•

Sowing1.

Fill

tray/pot

with

compost,

leaving

space

at

the

top,

level

the

compost

but

do

not

over

firm

it2.

Stand

in

water

to

allow

compost

to

soak3.

Allow

to

drain4.

Sow

seeds

at

the

required

depth

and

cover

as

necessary5.

If

seed

is

very

small

cover

with

e.g.

grit

or

vermiculite

to

ensure

contact

with

compost6.

Place

tray/pot

where

required7.

Place

in

the

light

when

germination

occurs

and

prick

out

as

soon

as

possibleSeed

propagationMeconopsis

nepalensis

germinating

after

2

weeks

warm

stratification

–

small

seed

placed

on

top

of

compost

and

covered

with

vermiculiteLigularia

japonica

seedcovered

with

gritSeed

propagation•

Calendula

officinalis‘Daisy

Mix

’•

Seed

quite

large

so

sown

direct

intomodules•

Will

be

potted

on

into

9cm

pots

for

plantingout

late

spring

forannual

beddingSeed

propagation•

Collecting

seed1.

Collect

as

soon

as

ripe1.

Watch

for

seed

pods

splitting2.

Catch

seeds

which

would

be

wind

blown

in

a

bag3.

Soak

fleshy

seeds

and

remove

seeds

from

the

flesh

and

dry

them.

Some

e.g

Prunus

or

Berberis

and

Cotoneaster

should

be

stratified

before

completely

dry.•

Storing

seed

(which

is

to

be

sown

not

saved

for

a

seed

bank)

1.

Collect

and

store

dry

seed

in

paper

bags2.

Store

in

dark,

dry,

airy

place3.

Keep

temperature

at

1

–

5°C

(34

-

41°F)Asexual

reproduction•

Exposing

the

cells

in

the

cambium

layer

to

encourage

them

to

divide

and

differentiate

leading

to

rooting

in

the

case

of

cuttings

and

layering,

and

in

the

case

of

budding

and

grafting,

a

union

between

the

scion

and

stock•

Cuttings:

woody,

soft

wood,

rootand

leaf•

Layering:

air,

simple,

natural,

serpentine,

tip,

trench•

Stooling•

Grafting:

budding,

T

budding,

Whip

and

tongue,

whip,

crown

(or

rind)CuttingsSalvia

involucrata

cuttingsSalvia

cuttings

taken

in

Octobertaken

in

AugustS.

involucrata

rootedCuttingsThermostatically

controlledpropagatorLayeringGrafting•

Cambium

layer

justbeneath

the

bark•

Ability

of

the

cells

here

to

divide

anddifferentiate

allows

buds

or

scions

of

other

plants

to

be

grafted

on

to

a

root

stock•

Whip

grafting

the