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 controlMeristematic 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

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

Make observations at least once a week on material such as internode length, flowering or cutting death.

Date / Observation

Final Observations

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 / Individual Ranking / Average Ranking/Treatment / % Rooted
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

General Notes

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
Mother of Thousands / Bryophyllum sp.
Jade Plant / Crassula argentea
Peperomia / Peperomia obtusifolia
Snake Plant
(Mother-Inlaws-Tongue) / Sanseveria trilsciata
Tip Cuttings and Stem Cuttings
Coleus / Coleus blumei
Geranium / Pelargonium x hortorum
Swedish Ivy
(Creeping Charlie) / Plectranthus australis
Zebrina / Zebrina pendula
Weeping Fig / Ficusbenjamina
Stolon with Plantlet
Spider Plant / Chlorophtum comosum

Name:Date: