Asexual Propagation
Objective
The purpose of this lab is to look at important factors in asexual
propagation. Students will look at different methods of cuttings including tip,
stem, and leaf. Students will also explore the role certain hormones contribute to
asexual propagation.
Introduction
Asexual or vegetative propagation includes: propagation by stolons
(strawberry), suckers (blackberry), layering (grape, honeysuckle, etc.), separation
(bulbs), division (rhizomes), cuttings (root, stem, leaf) grafting (apple), and
budding (pecan).
Asexual propagation (vegetative) results in clones, which are genetically
identical to the parent. Asexual propagation is possible because plant cells are
totipotent. That is, each cell retains the potential (and genetic information) to
generate an entire plant.
Dedifferentiation is the capability of mature cells to return to a
meristematic condition and develop a new growing point.
During asexual propagation, the plant part is wounded and the wound
response causes cell division resulting in identical cells (mitosis). The goal of
asexual propagation is the development of adventitious roots and shoots,
generally in a location where they normally would not form. Adventitious roots
are those arising from aerial plant parts. Adventitious shoots are those arising
from roots or other plant parts where they do not normally originate.
Reasons for Asexual Propagation
Preserve genetic make-up and perpetuate unique characteristics
(appearance, insect or disease resistance, drought tolerance,etc…).
Propagation of seedless plants, i.e. bananas, figs, seedless oranges
and grapes.
Avoidance of long juvenile periods as in Citrus which can take 5 to 10
years to bloom. Vegetative cuttings retain flowering capacity of the parent
plant.
Disease control Meristematic regions in shoot tips can sometimes
outgrow virus infections because of rapid cell division. These regions can
be excised and placed into tissue culture to propagate virus-free plants.
Combination of clones: grafting or budding.
Rapid production of some plant materials, especially trees.
Potential Disadvantage of Asexual Propagation
Asexual propagation may increase disease and insect susceptibility.
Clones lack the genetic diversity found in seed produced plants.
Part I Propagation by Cuttings
We will look at three different types of cuttage propagation: tip, stem and
leaf. Tip cuttings consist of a stem segment with the terminal bud intact. The
terminal bud has been removed for stem cuttings. Leaf cuttings include the
petiole and blade.
We will also look at the effect hormones have on rooting using a synthetic
auxin, IBA.
Materials
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Flats filled with potting mix.
Assorted plant material.
Pruning shears
Plastic labels
Methods
A minimum of 6 tip cuttings, 6 stem cuttings, and 6 leaf cuttings should
be made from the plants provided by your lab instructor (Figures 26 and 27).
Divide each cutting type into two groups. Place group 1 into the flat. Treat group
2 with IBA (auxin). Place your cuttings in a prepared flat of planting media.
Figure 28. Rooted stem cutting (left). Rooted tip cutting (right).
Figure 29. Rooted Leaf Cutting.
Part II Polarity
Polarity describes the development of roots and shoots on the ends of
cuttings which is correlated with their orientation on the parent plant.
Materials and Methods
Prepare a leaf from the Snake Plant as shown in Figure 28. Try to get 6
sections from a single leaf. Place half of the leaf cuttings in soil with the correct
polarity (“arrow” pointing up) and the other half with reversed polarity (upside
down). Make weekly observations and record your final observation in the below
tables.
Figure 30. Snake Plant leaf (A). After sectioning
and orienting to test polarity effects (B).
Part III Preformed Plantlets
Take 3-5 plantlets from the leaves of the Mother of Thousands and 1
plantlet from the Spider plant. Place in your flat. Make weekly observations and
record your final observation in the below tables.
Observations
Weekly Observations
1. Make observations at least once a week on material such as internode
length, flowering or cutting death.
Date
Observation
Final Observations
2. After cuttings have rooted, carefully dig up all cuttings and rank the rooting
response of each cutting from 1 (worst) to 5 (best). Calculate an average
rank for each treatment. Also at this time, determine the % rooted using
the below calculation:
# of Rooted Cuttings
x 100
# of Cuttings Originally Planted
Fill in the table below.
Containers will be provided for potting up your rooted cuttings.
Treatment
Control
Tip cutting
Stem cutting
Leaf cutting
IBA Treated
Tip cutting
Stem cutting
Leaf cutting
Snake Plant
Correct Polarity
Reversed
Polarity
Preformed
Plantlets
Mother of
Thousands
Spider Plant
Individual
Ranking
Average
Ranking/Treatment
% Rooted
General Notes
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Excess leaves should be removed but leave a couple of sets of
leaves at the top to provide the needed photosynthates for the
plant.
Avoid leaves touching the media surface (except in the case of Leaf
cuttings) as they will rot. Pinch out all flowers as they cause
excessive loss of water and energy.
Label your section with name and date.
Return all tools to the appropriate area.
Clean your work area thoroughly before leaving.
Recommended Plants for Cuttings
Common Name
Scientific Name
Leaf Cuttings
Bryophyllum sp.
Crassula argentea
Peperomia obtusifolia
Sanseveria trilsciata
Mother of Thousands
Jade Plant
Peperomia
Snake Plant
(Mother-Inlaws-Tongue)
Tip Cuttings and Stem Cuttings
Coleus blumei
Pelargonium x hortorum
Plectranthus australis
Coleus
Geranium
Swedish Ivy
(Creeping Charlie)
Zebrina
Weeping Fig
Zebrina pendula
Ficus benjamina
Stolon with Plantlet
Spider Plant
Chlorophtum comosum
Name:_______________________________________Date:________________
Asexual Propagation Worksheet and
Questions
Answer the following questions.
1. Name and describe three types of asexual propagation.
2. What is the hormone used to help promote root growth in asexual
propagation?
3. What are the two parts (structures) that can arise from asexual
propagation and are these adventitious?
4. Is asexual propagation actually cloning?
5. Which treatment had the best response? (e.g., highest average)
6. Did polarity have any affect on rooting the Snake Plant leaf?