PLSC 368 - Plant Propagation Name______Group______April 13, 2009 Lab Exercise 14
13. PLANT PROPAGATION BY BULBS AND CORMS
Note: The objective of this lab is to learn various types of underground organs that are used as plant propagules. Work as a team project.
1. INTRODUCTION
Bulbs and corms, although outwardly similar and functionally alike, differ in many aspects. Bulbs consist of a basal plate of stem tissue (containing apical bud and axillary buds) surrounded by either tunicate (as in onions and tulips) or non-tunicate (as in lily) bulb scales. These bulb scales compose the majority of the bulb and serve as food storage organs and in tunicate bulbs as a protective covering. On the other hand, corms consist mainly of stem tissue with an apical bud and several "axillary" buds on the corms surface that are protected by old leaf bases. In corms the swollen stem tissue acts as the food storage organ.
Bulbs reproduce by offsets that form from axillary buds between the scales of the bulb. Corms reproduce by the formation of corms and cormels, originating from apical and axillary buds, on the original corm which then dies. In many bulb or corm plants natural production of offsets or cormels is sufficient for commercial production. In others, bulb or corm production must be artificially stimulated by scooping, scoring, coring, sectioning or scaling.
2. PROCEDURES
A. Tunicate Bulbs (Laminate Bulbs): tulip, hyacinth, onion, daffodil, narcissus
a. Scooping
Remove the entire basal plate with cork borers or knife. Following scooping, dip the bulb in a fungicide to protect the cut surface. Place in a warm (21oC) dark location for approximately 2 weeks. When the scales begin to swell, move to a temperature of 30oC with a relative humidity of 85%. Plant new bulblets when new roots form.
b. Scoring
Scoring is accomplished by making 3 V-shaped cuts through the basal plate so that there are 6 pre-shaped sections. Cuts are made deep enough to destroy the main growing shoot and to reach just below the widest point of the bulb. Dip into a fungicide and bury upside down in clean, dry sand to 5 cm (2 in.). After wound tissues are formed on the cut surfaces, remove and treat as scooping.
c. Coring
Coring is accomplished by removing the center portion of the basal plate and the main growing point of the bulb. They are dipped in the fungicide and treated as scooped bulbs.
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d. Sectioning
Sectioning involves simply cutting into pre-shaped vertical sections, each with a piece of basal plate at its base . Treat with fungicide and as in scooping.
B. Nontunicate Bulbs (Scaly Bulbs): lilies
a. Use of bulb scales
Separate individual scales from the bulb and plant them in cell packs with peat-lite mix. Observe bulblet formation at the base of each scale.
b. Use of stem bulblets
Stem bulblets formed on mature plants grown in the greenhouse or in the field can be excised and used for propagation.
C. Corms: gladiolus, crocus
a. Use of cormels
Cormels naturally formed on the mother corms are separated and used as propagules. They are planted in the field and harvested as commercial corms in 2 years.
b. Sectioning of corms
Cut a corm into 3-4 vertical sections each containing at least one axillary bud. Dip them in fungicide. Follow the procedures used in bulb propagation.
3. OBSERVATION
Examine the formation of new bulblets on the mother bulbs which have been manipulated. Also examine cormel production on the sectioned corms in storage.
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