Questions for Dirr 17-42
1) What is cutting propagation?
Cut off some plant part (usually vegetative e.g. leaf, stem, root) and manipulate it to produce roots and
shoots
2) Is cutting propagation asexual or sexual?
Asexual
3) What is another word for asexual?
Vegetative
4) List and explain the three main reasons why cuttings are a common method for plant propagation.
a) Integrity of characteristics – maintain some desired feature through cloning
b) Economics – its relatively cheap and can produce high numbers (unsophisticated)
c) Avoid bud/graft incompatibilities
5) List and briefly describe the 3 primary types of cuttings?
a) Leaf – mostly for tropicals, little value in temperate woody plants, leaf bud cuttings are similar to
single node cuttings
b) Stem – divided into…see next question, most common for woody plants
c) Root – rare because of time and cost, works with suckering plants, polarity is important
6) Compare and contrast the following three primary types of woody plant stem cuttings:
a) Softwood – emerging shoots, spring, sensitive to desiccation, need cool and moist, best processed
in spring, follow a physiological calendar not temporal one, 2-5 inches long, several nodes, low
hormone concentration.
b) Semi-hardwood – most common, mainstay of woody plant prop, broadleaf evergreens and
deciduous and some needle evergreens, July-September, 3-6 inches long, remove ½ leaves or more,
less sensitive, easier to handle and stick
c) Hardwood – relatively unsophisticated, deciduous plants mostly, but needle evergreens and some
broadleaf evergreens qualify too. Many methods. Keep tops cool and root area warm for callus/root
development, ban saw 6 – 20” long, 2000-5000 ppm IBA
7) What’s the deal with root cuttings?
Suckering plants, polarity matters (use proximal end up), closer to trunk usually better (juvenility
influence), time consuming and expensive, smaller diameter=longer cutting.
8) What is the cone of juvenility?
Zone in the middle of plant that is older chronologically, but younger physiologically. Lack of leaf
abscission is a sign. This is a guide and not an absolute. Stronger and more apparent in some plants
than in others.
9) Ideally, when should cuttings be taken (time of day)?
Morning = highest turgidity. The more likely they are to desiccate the more important it is.
10) How should cuttings be treated with regards to temperature and moisture? Provide some methods one
could employ to achieve this.
Keep cool and moist. Plastic bag with ice and water works well or a cooler.
11) How quickly should cuttings be prepared and stuck after being severed from the parent plant?
ASAP. Can be held longer if cool and moist. Depends on season and type of cutting e.g. hardwood
cutting go for months.
12) How can one insure that they are propagating true-to-name plants?
Collect (steal) from named sources – botanical gardens, labeled gardens, nursery stock. Stock block
maintained juvenile is best.
13) How can cuttings be treated to avoid loss from fungal pathogens?
Dipped prior to sticking or flats drenched after.
14) Describe how each of the following factors will affect the rooting of a stem cutting:
a) Moisture status of the cutting (turgidity)
Must be high and remain high (mist system). Roots are gone, so we have to hold it in a state of
suspended animation and reduce any demand for water.
b) Carbohydrate status of the cutting
Must bring enough with it to initiate roots. Consider cutting size. Is bigger better? Where’s the balance?
c) General nutrition status of the cutting
All essential elements are important to plant growth and metabolism. Without roots and the ability to
take up what is needed, the cutting must be nutritionally strong (no deficiencies) at the time it is collected.
Fertilizing rooting cuttings is ineffective – no roots!
15) What is juvenility? How does it affect cutting success?
Tissue that is not reproductive is considered juvenile = no flowers or fruit and sometimes leaves are
different too. Generality – juvenile tissue roots better than reproductive tissue.
16) How does the time of year (season) affect cutting success?
Hugely! Depends on the type of plant and type of cutting. Some can go year-round while other have a
narrow window. Follow a physiological calendar!
17) What is orthotropic? What is plagiotropic?
Topophysis - Orthotropic = upright growth, plagiotropic = lateral growth. Doesn’t display in most plants,
but its cool.
18) What is wounding? How does it affect rooting of stem cuttings? Is it necessary?
Scar the stem to promote callus, promote internal rooting response, open cells to hormone, removes
physical barriers to root emergence. Usually not necessary. takes time and money.
19) Dirr’s description of girdling is very similar to what other propagation practice?
Layering – we’ll do this in a few weeks.
20) What is etiolation? When would it be used?
Extreme light exclusion. Technically, etiolation means the plant or plant part has never “seen”
normal light whereas blanching means removing light from a plant or plant part that has “seen” light.
Used on very difficult to root taxa.
21) What is auxin?
A class of plant hormones.
22) What are the two primary chemical compounds used in modern plant propagation?
IBA – indole-3-butyric acid
NAA – naphthaleneacetic acid
Both are synthetic auxins.
23) What is the best concentration of IBA for achieving success with woody stem cuttings?
2,500 to 5,000 ppm IBA
24) Compare and contrast talcs versus liquid hormone treatments for the propagation of stem cuttings.
Evidence that quick dips (liquid) are more effective than talcs. Liquid is immediately absorbed where
talc has to be solubilized. Beware solvent (alcohol) burn.
25) What is a quick-dip?
5 second dip of cuttings
26) If Wood’s rooting hormone is 1.03% IBA, how many ppm IBA is it? (Hint: Convert parts per
hundred to parts per million)
1.03% = 1.03 pph = 10300 ppm
Just set up a ratio 1.03/100 as ?/1,000,000
27) How many ounces of water would I add to 1 ounce of Wood’s rooting hormone (1.03% IBA) to
arrive at a 3000 ppm IBA solution? (Hint: Use the following formula.)
Concentration (before) × Volume (before) = Concentration (after) × Volume (after)
10,300ppm × 1 oz. = 3000ppm × ???
??? = 3.433 oz
Soooo 3.433oz – 1oz = 2.43 oz