PLS 3221L Plant Propagation Lab Dr. Mack Thetford
Unit 1. Greenhouse Orientation - An introduction to propagation facilities, containers, substrates and fertilizers.
During this first laboratory period, you will be introduced to the University of Florida greenhouses and to the class areas in which you will work this semester. The following topics will be covered during the laboratory:
A. Greenhouse guidelines
B. Facilities, equipment and various supplies used in propagation
1. Greenhouse structures
2. Benches
3. Greenhouse cooling and heating systems
C. Components of an Intermittent Mist System
1. Systems controlled by short interval clocks or a Solid State controller.
2. Systems controlled by an electronic leaf
D. Containers
1. Propagation and liner production
2. Post-liner production growing containers
E. Propagation substrates
1. Characteristics of an ideal propagation substrate
2. Characteristics of commonly used propagation substrates
F. Fertilizer use in propagation
1. General recommendations for propagation
2. Recommended levels of slow release fertilizers for propagation
G. Sterilization procedures for propagation substrates
H. Laboratory Exercise Outline
A. Greenhouse guidelines
1. Safety and sanitary procedures should be strictly followed at all times. This includes honoring all pesticide application, warning signs and respecting posted reentry times. All students must wear shoes at all times in the greenhouse.
2. If possible, please notify your instructor prior to any absence. The greenhouse is open Monday through Friday from 8:00 a.m. to 5:00 p.m. Incomplete lab work may be completed during these times. Each student is expected to complete all laboratory exercises.
3. The space assigned to you on the mist benches is for your use. If after you have finished installing your class experiments you have room in your flat for more cuttings and you have something you would like to try and root please bring it in. However, you may not exceed the space allotted to you.
4. Please do not tamper with the "electronic misting controller" or any other greenhouse controls. See your instructor if problems arise. Do Not turn off the mist system at any time.
5. Rooted cuttings and plants propagated by other procedures can be taken home upon completion of the experiment. When transporting these plants, use the substrate from the flat assigned to you. Do Not remove the flat from the greenhouse. Check with your instructor before taking cuttings rooted as part of a group project.
6. Courtesy for other classes and research activities should be maintained at all times. Do Not take cuttings, seeds or divisions from plants in the greenhouse without prior permission of your instructor. Many plants are part of on-going research projects or belong to other classes.
7. Direct all questions concerning class procedures to your instructor. Do not interrupt the campus landscape personnel unless an emergency situation exists.
8. Additional rules will be presented as part of your greenhouse orientation.
B. Facilities, equipment and various supplies used in propagation:
1. Greenhouse structures
a. Humidity chambers
b. Cold frames
c. Glass greenhouses
d. Pipe and pipe/wood frame or ridge and furrowed greenhouses
e. Lath houses
2. Benches
a. No benches
b. Expanded metal
c. Wood
d. Concrete
e. Plastics
3. Greenhouse cooling and heating systems
C. Components of an Intermittent Mist System
A wide array of options are available to the propagator with regard to both equipment and systems for multiplying plant materials. Commercial plant propagators utilizing greenhouse facilities typically include propagation benches covered with clear or translucent plastic tents or intermittent mist systems. Intermittent mist is generally more widely used in climates such as Florida. This is the method you will be using to study rooting of cuttings. Your instructor will point out the components of an intermittent mist propagation system and the optional controls for control and distribution of water.
1. Systems where water delivery is regulated by short interval clocks or a Solid State controller.
a. 24 hour time clock & short interval time clock - or
b. Solid State controller
c. Solenoid valve
d. Shut-off valve
e. In-line screen
f. Mist nozzle
2. Systems where water delivery is regulated by an electronic leaf.
a. Electronic Leaf (mercury switch)
b. Solenoid valve
c. Shut-off valve
d. In-line screen
e. Mist nozzle
Mist systems where water delivery is regulated by a 24-hour and short-interval clock or a Solid State controller.
Mist System where water delivery is regulated by an Electronic Leaf.
D. Containers
1. Propagation and liner production
a. Flats
b. Clay pots
c. Plastic pots
d. Fiber pots
e. Paper pots
f. Peat, fiber, expanded foam and rockwool blocks
2. Post-liner production growing containers
a. Plastic pots
b. Fiber pots
c. Polyethylene bags
d. Wood containers
E. Propagation Substrates
Propagation substrates include both naturally occurring and soilless substances and are extremely variable for such characteristics as water holding capacity, pH, buffering capacity and drainage. The characteristics of an ideal substrate are listed in the following table. Some of the more widely utilized substrate components and their characteristics are also listed in a table that follows.
1. Characteristics of an Ideal Propagation Substrate[1]
a. The substrate must be sufficiently firm to hold the cuttings or seeds in place during rooting or germination. Its volume must be fairly constant when either wet or dry; excessive shrinkage after drying is undesirable.
b. It should be highly decomposed to prevent nitrogen immobilization, and excessive shrinkage during production.
c. It must be easy to wet and it must retain enough moisture so that watering does not have to be too frequent.
d. It must be sufficiently porous so that excess water drains away, permitting adequate penetration of oxygen to the roots.
e. It must be free from weeds and weed seeds, insects, nematodes and various pathogens (bacteria, fungi, viruses, etc.).
f. It must not have a high salinity level.
g. It should be capable of being pasteurized with steam or chemicals without harmful effects (without influencing the physical, chemical and biological properties of the substrate such that the changes would be harmful to the plants being propagated).
h. It should have a high cation exchange capacity (CEC) for retention of nutrients that may be applied preincorporated and/or in a supplementary soluble and/or slow-release fertilizer form.
i. It should be of consistent quality from batch to batch, and reproducible.
j. It should be readily available and of acceptable cost.
F. Fertilizer use in propagation
1. General recommendations for propagation
Commercial propagators often preincorporate a controlled slow-release fertilizer containing both macro- and micro-nutrients into their propagation substrate. Other growers may apply a controlled slow-release fertilizer after sticking cuttings or planting seeds. The fertilizer is applied as a topdress or broadcast application (over the top). Still other growers may choose to apply a liquid form of fertilizer in gradually increasing concentrations; a method known as fertigation. These supplementary nutrients do not promote root initiation, but improve root and shoot development after root initiation has occurred. Supplementary fertilization is generally delayed until after cutting root growth has begun.
2. Recommended levels of slow release fertilizers for propagation.
· 6 lbs/yd3 Osmocote 18-6-12 (or any comparable product)
§ Nutricote
§ Polyon
· 1 lbs/yd3 minor element mixture
§ Micromax
§ Esmigran
§ Perk
§ FTE 503
· For nonrooted cuttings, fast germinating seeds and tissue culture plantlets, slow release fertilizers are preincorporated in the propagation media. For slower rooting or seed germinating species, Osmocote 18-6-12 can be broadcast at 0.5 oz/yd3
· Slow release fertilizers are top dressed on the substrate after rooting or seed germination starts to occur. Determining optimum levels of fertilization for propagation depends on the propagule system, and needs to be determined on a species basis.
G. Sterilization procedures for propagation substrates
a. Steam pasteurization is the principal sanitizing procedure employed by many greenhouses. Such systems need a steam generator, an intake mechanism, a covered area or container into which the steam is forced, a pressure gauge, and an escape outlet. Many greenhouses use a large fixed autoclave type sterilizer, two smaller fixed generated steam cabinets, wagons or carts through which steam is forced under pressure, and portable pipes and hoses for sterilizing greenhouse benches.
b. Chemical sterilization is a widespread practice using sodium hypochlorite (bleach) for plastic or metal containers and greenhouse benches that do not contain plants or propagation substrate. In addition, copper sulfate solution is utilized for sterilizing tools such as spades or trowels prior to their being used to move or mix the steam-pasteurized growing substrate.
H. Laboratory Exercise Outline.
Determining the Effects of Propagation Substrate on Rooting of Coleus.
The composition of propagation media has a dramatic effect on water and oxygen availability. Optimum rooting responses of various plant species may require media of differing water holding capacity or oxygen availability so it may be advisable to initiate a small experiment to determine the appropriate media to compliment your water delivery system. The following is an example of an experiment that can be utilized to compare various media as a propagation substrate.
Methodology: Place the media (substrates) in the flats provided utilizing one flat per two substrates. Prepare 20 cuttings of Solanostemon scutellaroides (coleus) for each substrate. Cuttings should be a uniform 3 inches in length, the bottom inch of the cutting should be stripped of leaves, and the cutting treated with Hormodin #1 (rooting hormone) prior to sticking. Place the flats under mist in the propagation house and water lightly to insure good substrate/cutting contact.
Record rooting data next week. The class should evaluate 10 cuttings from each substrate. You should do this with all students present. All students are responsible for obtaining the rooting information for all substrates. Record your data on the data sheet provided and summarize. In your discussion be sure to discuss the relative degree of water holding capacity of the various media and how that may have influenced the overall root quality or timing of rooting.
A few notes on data calculations.
1. Rooting percentage is based on the total number of cuttings stuck so you will divide the number of cuttings with roots by ten.
2. Root number per cutting is based only on rooted cuttings. You would determine an average number of roots per rooted cutting.
3. Root length (length per root or root length per cutting) should only be based on rooted cuttings. You would determine an average length per root per rooted cutting for each treatment.
On the following data sheet, enter the data from your propagation study. From this data, summarize the results of your experiment and conclude if the propagation substrate influenced the success of rooting. In your final summary report comment on rooting percentages, root numbers and root lengths of the cuttings over the length of the study. You may need to make a copy of this data sheet to complete your data collection.
I. Laboratory Questions - Unit 1
Each laboratory exercise will include questions for you to answer. These questions are to be answered on a separate sheet(s) of paper and turned in at the beginning of the following week's lab. (30 points total)
1. What are three substrates used in the class propagation flats? (3 points)
2. What is the function of the solenoid valve in an intermittent mist system? (2 points) Explain how the solenoid valve (normally closed) operates. (2 points)
3. Excluding electrical power failure, briefly discuss 4 problems that may arise in the operation of an intermittent mist system. (4 points)
4. How might plastic pots be sterilized? (1 point)
5. Please list three reasons why soil is not a good greenhouse propagating substrate. (3 points)
6. What are the proper steps in utilization of trowels and spades for mixing substrates. (2 points) What precautions must be taken to insure that these tools do not become contaminated between uses during the laboratory period. (2 points)
7. Why is sterilization of substrate, tools, greenhouse benches and containers important. (4 points)
8. Explain how a "mechanical leaf" functions to regulate mist application. (2 points)
9. In place of a "mechanical leaf", the timing of mist application could be regulated by 2 time clocks. Explain how each of these two time clocks function in replacing a "mechanical leaf". (2 points)
10. List three types of containers suitable for direct propagation of plants by cuttings. (3 points)
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[1] Adapted from Plant Propagation principles and practices. Sixth Edition, 1997. Hartman, Kester, Davies, and Geneve, editors. page 68.