Introduction: (Initial Observation)
There are many plants that grow, reproduce and cover a large area, forming forests and savanna. However there are other plants that do not easily reproduce and need human intervention. Knowing how do the plants reproduce can help us to manage our natural environment by increasing helpful plants and preventing reproduction of weeds and undesirable, unattractive, or troublesome plants.
Information Gathering:
See the information in the green section, at the bottom of this page.
Find out about different methods of plants reproduction. Read books, magazines or ask professionals who might know in order to learn about these methods. Keep track of where you got your information from. A local nursery may be a good place to start.
Question/ Purpose:
The purpose of this project is to find out how do plants reproduce and perform some experiments showing the reproduction process.
Identify Variables:
Variables that may affect the reproduction of plants are the same variables that affect the plant growth. Temperature, light, water and nutrition are among such variables.
In this project we will not study the effect of these variables on plant growth, however for higher grades this may be required.
Hypothesis:
Based on your gathered information, make an educated guess about how do certain plants reproduce. Your hypothesis can be about a tree, a house plant or any other type of vegetation.
Experiment Design:
Design an experiment to test plants reproduction.
Experiment 1:
(To identify the plants that can be reproduced by their seeds?)
Collect samples of beans that you might have at home. Use 5 small pots and grow 2 identical beans in each pot. You may purchase small ceramic pots from nurseries or craft stores (a few cents each) or you can use small paper cups or plastic cups instead. Pots or cups must have a small hole at the bottom for excess water to exit. You can use soil, wood dust or even paper towels as a media to grow beans. These material will hold water or moisture needed by the plant. Soil will also have some nutrition that paper towel does not have. If you use paper towel, first cut it in small pieces and then use it as growth media.
In each pot put some media (such as soil), place two beans and cover the beans with some additional soil. Make sure that you do it the same for all five samples. Name each pot with the name of beans in that pot. Now you need to start adding water. Water your pots once or twice a day for about 3 weeks.
Keep your pots in a warm place with enough light.
Experiment 2:
Which house plants can be reproduced by by cutting?
Cut and plant the stems of different house plants that you have access to. Record the date and the time for each sample and continue your daily observation and report.
For best results, cuttings are planted in rooting media. However for your experiment you can plant it in a clear jar so you can see the production of new roots and record it. Also instead of soil or rooting media use water and small amount of a fertilizer such as ammonium nitrite. You can also test jelly plus some fertilizer as your rooting media, it may create a nice display.
More Details on
Propagation of Plants by Stem Cuttings
If you want to do it in professional way
One inexpensive way to obtain new plants is by taking cuttings. Here we explain how to get good results from propagating stem cuttings using a rooting medium.
Rooting Media
It is important to use a good sterile rooting media to get your plants off to a healthy start. Soil or compost are not good choices to use since they may harbor diseases. You can purchase ready to use seed starting mixes from your local nursery and use it as rooting media.
You’ll also need sharp scissors or pruners, labels, pots and clear plastic bags. The plastic bag is used to cover the cuttings to keep humidity up around the plants while they are forming roots since they will have no way to replace water lost through transpiration. You can also purchase trays with clear plastic domes if your pots and cuttings are not too tall.
Softwood Cuttings
For beginners, softwood cuttings are good to start with since they are the easiest. Cut new growth from the plant in late spring or early summer. Many shrubs and trees root well using this method. Since plants are making most of their growth at this time of year it also follows that they will also make good root growth.
If you plan on taking cuttings in another location, bring a plastic bag so you can keep the cuttings sealed in the bag until you get it home. Cut the stems at an angle to give the cuttings more cut surface to form their roots.
Most cuttings root best if the cut is made ½ inch below the leaf node. Strip the leaves off the lower parts of the stems leaving only the top leaves. If the leaves are large on top cut them leaving only half a leaf.
With a spoon handle or pencil make a depression in the soil for the stem to fit into. If you use a rooting hormone first dip the stem in the powder then slip the stem into the hole you made in the soil. After placing the cuttings in the soil, firm the soil around the roots. You can place several cuttings in the same pot. After you plant the cuttings place the pot in a tray of water. Let it soak up the water until the top of the soil is visibly moistened. Remove the pot from the water and let it drain, then place in a plastic bag and seal it shut. Set it in a bright window without direct sun. Open the bag up for about ten minutes each day to let fresh air circulate.
Cuttings can vary in how long they take to grow their own roots. Some plants can set roots almost immediately, while others can take weeks before roots will form. After about a week start checking if the roots are growing by gently tugging the stem. If you meet resistance the roots are forming. At this point take them out of the bag and give them a weak solution of fertilizer. Most of the cuttings are placed in the ground by fall, excepting fuchsias and other fast growing plants.
1-Find a leaf node
2-Remove extra leaves
3- Cut in angle
4- insert in hormone
5- Plant in rooting media
Materials and Equipment:
Extract the list from the experiments that you select.
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
Description
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
References:
List of References
Optional and additional information for this project.
SEXUAL PROPAGATION OF PLANTS
Sexual propagation involves the union of the pollen (male) with the egg (female) to produce a seed. The seed is made up of three parts: the outer seed coat, which protects the seed; the endosperm, which is a food reserve; and the embryo, which is the young plant itself. When a seed is mature and put in a favorable environment, it will germinate, or begin active growth. In the following section, seed germination and transplanting of seeds will be discussed.
Seed
To obtain quality plants, start with good quality seed from a reliable dealer. Select varieties to provide the size, color, and habit of growth desired. Choose varieties adapted to your area which will reach maturity before an early frost. Many new vegetable and flower varieties are hybrids, which cost a little more than open pollinated types. However, hybrid plants usually have more vigor, more uniformity, and better production than non-hybrids and sometimes have specific disease resistance or other unique cultural characteristics.
Although some seeds will keep for several years if stored properly, it is advisable to purchase only enough seed for the current year use. Good seed will not contain seed of any other crop, weeds, seeds, or other debris. Printing on the seed packet usually indicates essential information about the variety, the year for which the seeds were packaged, and germination percentage you may typically expect, and notes of any chemical seed treatment. If seeds are obtained well in advance of the actual sowing date or are stored surplus seeds, keep them in a cool, dry place. Laminated foil packets help ensure dry storage. Paper packets are best kept in tightly closed containers and maintained around 40° F in a low humidity.
Some gardeners save seed from their own gardens; however, such seed is the result of random pollination by insects or other natural agents, and may not produce plants typical of the parents. This is especially true of the many hybrid varieties. (See Vegetables chapter for information on saving vegetable seed.) Most seed companies take great care in handling seeds properly. Generally, do not expect more than 65% to 80% of the seeds to germinate. From those germinating, expect about 60% to 75% to produce satisfactory, vigorous, sturdy seedlings.
Germination
There are four environmental factors which affect germination: water, oxygen, light, and heat.
Water
The first step in the germination process is the imbibition or absorption of water. Even though seeds have great absorbing power due to the nature of the seed coat, the amount of available water in the germination medium affects the uptake of water. An adequate, continuous supply of water is important to ensure germination. Once the germination process has begun, a dry period will cause the death of the embryo.
Light
Light is known to stimulate or to inhibit germination of some seed. The light reaction involved here is a complex process. Some crops which have a requirement for light to assist seed germination are ageratum, begonia, browallia, impatiens, lettuce, and petunia. Conversely, calendula, centaurea, annual phlox, verbena, and vinca will germinate best in the dark. Other plants are not specific at all. Seed catalogs and seed packets often list germination or cultural tips for individual varieties. When sowing light-requiring seed, do as nature does, and leave them on the soil surface. If they are covered at all, cover them lightly with fine peat moss or fine vermiculite. These two materials, if not applied too heavily, will permit some light to reach the seed and will not limit germination. When starting seed in the home, supplemental light can be provided by fluorescent fixtures suspended 6 to12 inches above the seeds for 16 hours a day.
Oxygen
In all viable seed, respiration takes place. The respiration in dormant seed is low, but some oxygen is required. The respiration rate increases during germination, therefore, the medium in which the seeds are placed should be loose and well-aerated. If the oxygen supply during germination is limited or reduced, germination can be severely retarded or inhibited.
Heat
A favorable temperature is another important requirement of germination. It not only affects the germination percentage but also the rate of germination. Some seeds will germinate over a wide range of temperatures, whereas others require a narrow range. Many seed have minimum, maximum, and optimum temperatures at which they germinate. For example, tomato seed has a minimum germination temperature of 50oF and a maximum temperature of 95o, but an optimum germination temperature of about 80o. Where germination temperatures are listed, they are usually the optimum temperatures unless otherwise specified. Generally, 65o to 75oF is best for most plants. This often means the germination flats may have to be placed in special chambers or on radiators, heating cables, or heating mats to maintain optimum temperature. The importance of maintaining proper medium temperature to achieve maximum germination percentages cannot be over-emphasized.
Germination will begin when certain internal requirements have been met. A seed must have a mature embryo, contain a large enough endosperm to sustain the embryo during germination, and contain sufficient hormones or auxins to initiate the process.
ASEXUAL PROPAGATION OF PLANTS
Asexual propagation does not involve exchange of genetic material, so it almost always produces plants that are identical to a single parent. Delicious apple and Bartlett pear are two examples of species that have been asexually propagated for decades. Asexual propagation methods include cuttings, layering, division, grafting, budding and tissue culture.
CUTTINGS
Cuttings involve removing a piece from the parent plant and that piece then regrows the lost parts or tissues. Both woody and herbaceous plants are asexually propagated by cuttings of stems, leaves and roots. New plants can be grown from parts of plants because each living plant cell contains the ability to duplicate all plant parts and functions. Mature cells can change into MERISTEMATIC (mare-ah-ste-MAT-ick) cells that are found at rapid growth sites like buds.
There are many types of cuttings. Often, a plant can be propagated by more than one method of cutting. Some plants will reproduce readily from cuttings and others take a considerable amount of time and care.
STOCK PLANTS are the parent plants used in asexual propagation. Stock plants must be in excellent health and should possess characteristics desirable for production of new plants. Herbaceous cuttings are those taken from nonwoody plants, such as perennials and houseplants.
Softwood cuttings are pieces of new growth taken from woody stock plants. These cuttings must be taken before the new growth starts to harden. Hardwood cuttings are taken from tissue which has become woody. Other forms of cuttings are leaf cuttings and root cuttings.
The gardener must try to duplicate the conditions needed for a plant to root from a cutting. High humidity, indirect light and soil temperatures of 70 to 80 degrees F are best for most cuttings. These conditions may be created by keeping cuttings enclosed under glass or in plastic bags in dappled shade. Cuttings must be shielded from direct sunlight, especially if they are under glass or plastic.
STEM CUTTINGS
When a cutting is made, injured xylem and phloem cells plug the tubes so that precious fluids are not lost. Usually a CALLUS forms at the cut. Cells near the callus area reorganize to form adventitious roots.
Stem cuttings are the most commonly used method to produce houseplants. Select vigorous, new growth with no flower buds. Stem sections should be free of diseases and insects. Each cutting should be 2 to 4 inches long and have 2 or 3 leaves attached.
Make a cut 1/4 inch below a leaf node and pull off the leaves that are at the nodes that will be below the surface of the rooting medium. ROOTING HORMONE helps to stimulate rooting, but is optional. Pour a small amount of the rooting hormone into a clean container to prevent contamination of all of your rooting hormone. Dip the base of the stem, including the node area, into the rooting powder. The stem should be dry when dipped.
Commercial rooting products often include a fungicide. This is a good idea given the damp conditions required for rooting success. Tap off excess powder, since too much hormone can inhibit rooting.
Poke a hole in the medium before inserting the cutting to avoid loss of the rooting hormone. Insert treated cutting in a moist rooting medium. A suitable rooting medium is half perlite and half sphagnum peat moss. Any disinfested container with drainage is acceptable for use.
Cover container and cutting with a plastic bag tent to maintain high humidity. Place unit in a warm area with indirect light. Check the rooting medium every few days to make sure it remains moist. Rooting can take from a few days up to several months.
After a few weeks, test for rooting by gently tugging at the cutting. If there is resistance, rooting has started and the plastic cover may be removed. More detailed instructions on stem cuttings are provided in Fact Sheet 1226, Reference Prop.1.
LEAF CUTTINGS
In this method, a leaf blade or leaf with petiole is used to propagate new plants. The same steps are followed as for stem cuttings. Choose a healthy leaf from a vigorously growing plant. Cut it close to the stem with a sharp, disinfested razor or knife. Trim off 1/4 of the leaf and dip into rooting hormone, if desired. Insert the leaf into rooting medium so that 1/3 of the leaf is below the surface.
One or many new small plants form at the base of the leaf. African violet leaves will produce many new plants. Begonia leaves can be divided into segments for propagation; however each leaf piece must contain a major vein. With leaf cuttings, the original leaf is not a part of the new plant and is usually discarded.
Many succulent plants, such as sedum, jade, and peperomia, can be propagated by leaf cutting. Some plants such as Kalanchoe pinnata or K. bryophyllum, piggy-back or air plants, form their own new plantlets in this fashion. See Fact Sheet 571 on leaf cuttings, Reference Prop.2.
ROOT CUTTINGS
Cultivation of root cuttings probably started after gardeners observed new plants growing from pieces of root accidentally left behind in the soil. Take cuttings from newer root growth. Make cuttings 1 to 4 inches long from roots that are 1/4 to 1/2 inch in diameter. Be sure that the roots collected are from the chosen plant and not neighboring plants.
Cuttings should be taken during the dormant season when roots have large carbohydrate supplies. However, they also may be taken throughout the growing season. Cut straight through the end of the root closest to the stem. Cut the other end on a slant. This allows you to remember which end is the top (the straight cut) and which is the bottom (the diagonal cut).
Store cuttings from dormant roots for 3 weeks in moist rooting medium at 40 degrees F. Remove from storage and plant upright in the growing medium. Keep moist and warm, in a bright location until growth and weather permit acclimatizing to the outdoors.
If root cuttings are taken during active growth, skip the storage period and place cuttings directly in the rooting medium. For smaller plants, take 1- to 2-inch sections. Place cuttings horizontally a half inch below the surface of the rooting medium. These cuttings should be handled indoors or in a HOTBED. The fine roots of many perennials are used for propagation. Root cuttings of some variegated plants will lose their variegation.
SOFTWOOD AND HARDWOOD CUTTINGS
Softwood cuttings are taken from first-year branches that have not yet become woody. Flowering shrubs are often propagated by softwood cuttings. Late spring and early summer are the best times for success with this method. Take cuttings after it rains or water is applied in the cool morning. Make a diagonal cut. The larger diagonal cut gives more area to develop roots. Keep cuttings in water before moving them into rooting medium.
Make cuttings 2 to 10 inches long. Larger cuttings produce larger plants sooner. Make cuts slightly below a leaf node. Follow the same instructions for disinfested containers, rooting medium and light and moisture conditions used by other cutting methods. Rooting hormones may be used with this method. The base of the cutting should be dry before dipping it into rooting hormone powder.
Hardwood cuttings are taken once the tissue becomes woody and the plant is dormant. Cuttings can be taken anytime from late fall after a killing frost until late winter. Select healthy wood that was produced the previous summer. Several cuttings can be made from the same branch of some shrubs.
Make cuts at a slant, 5 to 12 inches long. Basal cuts should be just below a node, while the upper cut should be slightly above a bud. Dip the basal end in rooting hormone. Mark the most terminal end of each cutting with a tag.
Bury cuttings vertically in moist vermiculite or sand. Cuttings should not freeze, but must remain cool. A callus will form on the lower cut end during storage. Callus formation indicates that cuttings are ready to root.
In spring, remove the cuttings from storage. Plant in a hotbed or other protected site with morning sun exposure or filtered light. Leave 1 to 2 inches of cutting above ground. Keep cuttings moist until a root system forms. Transplant the cuttings the following spring while they are still dormant.
LAYERING
Layering causes roots to develop on shoots that are still attached to the parent plant. The stem is not cut from the main plant until it has rooted. Use this method when other propagation methods are unsuccessful. Layering is a good propagation choice when only a few plants are needed.
Simple layering is done by bending a branch to the ground and burying a portion of it. The tip remains uncovered. A light soil increases rooting success, as will wounding or girdling the buried section. Treatment with rooting hormone is helpful.
Hold the branch in place with a rock or peg. Layering is done in early spring while plants are still dormant or in late summer on wood that has not become woody. Plants with flexible branches are particularly suited to this method.
Other types of layering include serpentine or compound layering, continuous or trench layering, and mound or stool layering.
Fact sheet 1091, Reference Prop.3, is on air layering.
DIVISIONS
Division is the cutting or breaking up of a crown or clump of suckers into segments. Each segment must have a bud and some roots. These segments are replanted and grow into new plants identical to the parent. Most perennials should be lifted and divided when they become overgrown and begin to lose vigor. Vigorous growth in most perennials occurs on the outer segments of the clump. Old growth in the center of the clump is discarded.
Carefully dig the plant, loosening the roots and lifting the plant from the soil. Split apart the main clump with two spades or forks or chop with a shovel or hatchet if the clump is firmly massed. In some cases outside segments of the plant can be removed and replanted without disturbing the rest of the plant.
A good rule of thumb is to divide fall-flowering perennials in spring and spring- and summer-flowering perennials in fall.
Some shrubs that form clumps or crowns are suitable for division. Divide in early spring while dormant. Shrubs used for division should have several clumps that are two years old or older.
BULBS AND CORMS
Bulbs can be propagated by removing small bulblets or offsets that form at the base of the parent bulb. These small bulbs take 2 or 3 years to mature into plants that flower. Place offsets in rich, light soil for their development. This same procedure should be followed for plants which form from corms, such as gladiolus.
Many lilies can be multiplied by removing scales from the mature bulb. Dust the scale with a fungicide and place, base end down, in a moist growing medium in a warm, protected area. Bulblets will form at the base of the scale. In 1 to 4 years these bulblets will grow and be ready to flower.
TUBERS AND RHIZOMES
Tuberous plants can be dug up and the TUBERS separated. In separating the tubers, each must have a segment of the crown that contains at least one eye or bud.
Rhizomes grow and develop buds along their length. The rhizomes can be dug and cut into sections that each contain at least one eye or bud.
GRAFTING
Grafting involves the joining of different segments of two different plants of the same species. A branch or bud is joined to an UNDERSTOCK. In grafting, the cambium layers of the two different segments are aligned and grow together. Some plants graft naturally. Ivy commonly grafts itself. Natural grafting occurs where two branches are in close contact over several years.
Grafting allows gardeners to produce plants identical to a parent plant. It also allows growers to control size and shape of a tree or shrub. Apples are grafted onto root stock that regulates the ultimate size of the tree.
Grafting can produce more vigorous, earlier fruiting, or two varieties can be grown on the same tree to provide pollination as with apples.
On the negative side, some grafting attempts will be rejected. This is called graft incompatibility. This might not occur in the first year, but may in successive years. Wind or winter cold can damage a GRAFT UNION. Some grafted trees or plants produce large numbers of SUCKERS. These can crowd out the desired plant or tree and are unsightly. If the graft union is planted below the soil surface, the SCION will root and the rootstock will die.
Grafting is usually done in the spring. It involves collecting small branches called scion wood. These branches are 1/4 to 1/2 inch in diameter. Gather them several weeks before grafting is to occur. Collect wood that grew the preceding year. Select only wood with leaf buds, not flower buds.
Scion wood should be gathered in winter when wood is dormant, but not frozen. Use sharp clippers so that wood is not crushed. New growth over 1 foot in length is usually best.
Discard the wood at both ends of the branch and use the middle section. End growth is too succulent for grafting and wood closer to the base will graft more slowly. Label the scion wood, wrap it in moist paper towels or sphagnum peat, enclose it in an airtight, plastic container and place it in the refrigerator.
Scion wood must be joined to the understock in spring when buds swell. It is critical that the two pieces are nearly the same size and that sap has begun to flow. The day before actually grafting, remove scions from the refrigerator and snip off the bottom ends. Place the clipped scions in a pail of water overnight.
It is critical that the cambium layer on the scion precisely matches that of the understock.
For precise directions on joining scion to understock, see Fact Sheet 760, Reference Prop.4. Grafts can be placed on a root or stem and be joined by any of several methods. The union is held firmly in place using wax, tape, plastic wrap, rubber bands or plastic tubing.
The grafted area must be protected from anything that will move the scion out of alignment. Bracing some grafts is advised. Side sprouts should be removed the first summer. Sucker shoots that sprout from below the graft also should be removed. If growth of new graft is satisfactory, do not fertilize the plant during the first year. There is danger that top growth will be very brittle and it could fail to harden off before the first frost.
BUDDING OR BUD GRAFTING (Click here to See details)
Bud grafting is faster, easier and less messy than other forms of grafting. Cambium layers do not need to be aligned. Bud grafting is done from early July through early August. This method uses a newly developed LATENT BUD, taken from under a live leaf.
Budwood is collected from healthy branches that grew since spring. Young trees offer good budwood because they produce a large amounts of new growth. Use buds from the middle section of the branch.
Remove leaves, but keep 1/4 inch of the leaf’s petiole for grasping. The bud is cut from the branch and inserted into a T-shaped slice made in the bark of the understock. Budding should only be done when the bark slips easily away from the tree. The bud is held in place with special tape or wrap.
MICROPROPAGATION OR TISSUE CULTURE
Each plant cell has the potential to grow into a new plant exactly like the parent. This fact coupled with technical advances, specialized equipment and sterile laboratory conditions has produced modern tissue culture.
In tissue culture, individual or small groups of plant cells are manipulated so they each produce a new plant. A tiny piece of bud, leaf or stem can produce incredible numbers of new plants in a small space in a short time.
The advantages of tissue culture, in addition to speed and efficiency of propagation, include production of disease-free plants. New plants can be made available to the public more quickly because of tissue culture.
However, there are some problems with spontaneous mutations which naturally occur. In tissue culture, the incidence of these mutations is greatly increased.
Conditions for tissue culture are very exacting. Absolutely sterile conditions must be maintained. Temperature, light, humidity and atmosphere are strictly controlled with electronic sensors and computerized controls. Such costly equipment rules this out for most home gardeners.
