22.1 plant cloning

What is natural plant cloning method 

Vegetative propagation

What is vegetative propagation 

When a parent plant produces genetically identical offspring (clones) from a non-reproductive tissue/ vegetative organ (e.g. from roots, stems, leaves rather than the seed) via asexual reproduction 

How do vegetative organs produce identical clones 

They contain meristematic tissue, undifferentiated stem cells, that undergo mitosis to differentiate into new roots, stems and leaves 

What are 4 parts of a plant that undergo vegetative propagation

Bulbs 

Runners (stolons)

Rhizomes 

Tubers

What is a node 

Point on a plants stem where buds (that develop into new roots, shoots, leaves, flowers) grow from

What are tubers and give an example 

e.g. potatoes (stem tubers), sweet potato (root tubers) 

underground swollen roots that form tubers which have ‘eyes’ which sprout into a new plant 

How does a tuber form a new plant 

during summer parent plant pumps excess sugars underground causing roots to swell up into tubers > stem tubers have small pits called eyes, inactive buds with meristematic tissue that uses uses starch inside the tuber for respiration during spring to fuel mitosis > new shoots sprout and grow upward out the soil and roots grow downward to establish new clone plant 

What are bulbs and give examples 

e.g. garlic, onion, daffodils 

underground swollen leaves with internal bud inside 

How does a bulb form a new plant 

fleshy leaf layers are packed with starch and at the very center sits the apical bud which uses the stored starch to form new leaves and flowers & lateral buds that split away from main parent plant and grow into separate identical plants 

What are rhizomes and give an example

e.g. marram grass, ginger 

Stems which grow horizontally beneath the soil from parent plant

There are nodes along the stem with vertical buds where new roots (grow further downward into soil) and shoots (grow upwards and emerges from soil) forming new plant 

What are runners (stolon) and give an example

e.g. strawberry plants 

Stems which grow horizontally above the soil from parent plant 

There are nodes along the stem with vertical buds where new roots (downward into soil) and shoots forming new plant 

What is the aim of runners and rhizomes 

Spread out sideways away from parent plant so a new independent and genetically identical clone grows at the nodes 

Why are bulbs and tubers referred to as perennating organs 

They act as storage organs (storing starch) found underground which enable the plant to survive ‘perennate’ during harsh winter conditions and to regrow from one season to the next

What are the 2 artificial plant cloning methods

Taking cuttings 

Microprogagation 

What is taking cuttings also referred to as 

Artificial vegetative propagation  

What is taking cuttings 

-cutting a section of a non flowering stem to produce a genetically identical clone

Outline process of taking cuttings 

1. Cut - Cut a non-flowering stem at a slant (increases SA and prevents xylem collapsing) between the nodes 

2. Rooting powder - Dip cut end in rooting powder with plant hormones e.g. auxins to stimulate cell division therefore root growth

3. Remove leaves - only leave 2-4 as this limits concentration of stomata which reduces transpiration 

4. Pot - pot into soil and add water (ensuring its controlled amount to not saturate soil)

5. Plastic bag - cover with a bag to increase humidity which reduces transpiration 

Why is cuttings taken from a nonflowering stem 

-to promote the growth of roots 

Why is cuttings taken between the nodes 

-because that means there will be a bud that will develop into a genetically identical clone of parent plant

What is micropropagation 

Producing large amount of genetically identical offspring plants from a single parent plant using tissue culture technique 

What is a tissue culture 

Growing plant tissues in a sterile and nutrient rich medium with minerals, sugars, vitamins and growth hormones e.g. auxins AND cytokinins to stimulate cell division (mitosis) and growth 

Outline process of micropropagation 

1. Collection - explant (small sample of meristem tissue) is taken from the shoot tip or apical bud of the parent plant 

2. Sterilisation - use aseptic techniques to sterilised explant to remove/ inhibit the growth of any contaminants e.g. bacteria 

3. Culture - explant cultured in nutrient rich medium containing minerals, sugars, vitamins and growth hormones for cell division and growth 

4. Development - cells in explant divide to form callus (undifferentiated mass of identical cells)

5. Transfer - callus cells are divided and placed in a new medium with specific conditions to encourage shoot and root formation enabling cells to differentiate and develop into genetically identical plantlets 

6. Pot - fully formed plantlets with shoots and roots are potted in compost to develop into mature plants identical to parent plant 

What important property do meristem cells have 

They are totipotent so can differentiate into any type of plant cell

State advantages of micropropagation 

:) fast production (than growing from a seed) and higher yield of genetically identical plants compared to vegetative propagation  

:) propagation of: rare plants, plants with desirable traits, seedless plants, pathogen-free plants 

State disadvantages of micropropagation 

:( lack of genetic variation as they are a monoculture (genetically identical) therefore greater risk/ more susceptible to disease and environmental changes

:( if parent plant is infected, the offspring plant will also be infected with those microorganisms 

:( expensive and requires skilled technicians