Propagation of Flowers and Ornamental Plants by Specialized Vegetative Structures

Transcription

1 Propagation of Flowers and Ornamental Plants by Specialized Vegetative Structures A. Vegetative Propagation Vegetative propagation is the perpetuation and multiplication of plants through different vegetative plant organs like sucker, tuber, corm, runner, rhizome etc. B. Specialized Vegetative Structures B.1. Bulb A bulb is a modified orthotropic underground stem consisting of basal plate (bottom of bulb from which roots grow), a terminal bud and numerous scale leaves (swollen bases of foliage leaves). Cluster of fibrous roots develops at the base and it has no distinct nodes or internodes. The terminal bud grows into the aerial shoot and lateral buds develop into bulblets. There are two types of bulbs. B.1.1. Tunicate bulb: This type of bulb consists of concentric layers of tightly arranged scales, the outermost layer being a dry, membranous protective layer. B.1.2 Scaly bulb: Scaly or non-tunicate, bulb lack an outer dry protective membrane. The scales are not tight but loose and can be removed individually from the bulb. Examples: Daffodil, Hyacinth, Iris, Lily, Tuberose, Tulip etc. Propagation: Each bulb consisting two or more bulblets where they are separated and planted from which a new plant grows up. B.2. Bulbil Bulbil is a modification of vegetative bud or floral bud that forms in an axil or in place of flowers. These appear at first as small nodule like buds, beginning near the bottom of the stem and continuing up. Examples: Lily, Agave, Wood sorrel etc. Propagation: Bulbils can be harvested once when they matured and planted as a normal bulb in the soil. In any case it sheds from the mother plant and grows up into a new independent one. B.3. Corm Corms are short, swollen underground stem growing in the vertical direction. It is more or less rounded in shape or often flattened from top to bottom. It bears one or more buds in the axils of scale leaves and an optical bud. The optical bud will develop a new leafy plant, while the buds in the scale leaves form new corms. The corm contains a basal plate, growing point and lateral bud develop into cormel. Examples: Amorphophallus, Colocasia, Crocus, Gladiolus etc. Compiled by: Md. Dulal Sarkar Lecturer, Department of Horticulture Sher-e-Bangla Agricultural University Page 1 of 7

2 Propagation: Each corm produces new corms and cormels on old ones, which are used for multiplication. B.4. Crown Crown is the part of a plant between stem and root from which new shoots arise and adventitious roots develop along the base of the new shoots. Examples: Bamboo, Lily, Sansevieria etc. Propagation: Cut back to the crown in the early summer that increases the production of shoots. It should be done at the beginning or end of the growing season. B.5. Offset An offset or offshoot is a short, more or less thickened, prostrate branch that develops from the base of the main stem usually starting from an axillary bud. Apex turns up and produces a tuft of leaves above and a cluster of roots below. Examples: Cymbidium, Dendrobium, Water lettuce, Water hyacinth, Salvinia etc. Propagation: Cutting the offset close to the main stem with a sharp knife which can be planted and grown as independent plants. If it is well rooted it can be potted, if not the shoot is placed in a favourable rooting medium. B.6. Rhizome Rhizomes are thickened, prostrate, swollen, underground modified stem, distinguished from the root by the presence of distinct nodes and internodes. It has scaly leaves at the nodes, a bud in the axil and a terminal bud. But it has no basal plate. The stem is branched and usually grow horizontally just below or at the soil surface. Examples: Anthurium, Calathea, Canna, Couch Grass, Ferns, Iris, Lily, Orchid etc. Propagation: Cutting the rhizomes into sections and each piece has at least one bud or eye. Each one will produce new plant. B.7. Runner Runner is a slender, elongated, prostrate, aerial stem with long internodes, creeping on the ground, and rooting at the nodes. Examples: Centella, Cynodon, Fern, Orchid, Marsilea, Spider plant, Wood sorrel etc. Propagation: Cutting the runner into pieces with adventitious roots from lower surface of nodal regions and each piece will produce new plant. B.8. Stolon Stolon is a slender, elongated, plagiotropic stem arise from the base of the underground stem. It bends down on or into the ground and, then strikes roots and develops a bud at each node which grows into a new plant. Examples: Colocasia, Dracaena, Tecoma, Water dropwort etc. Page 2 of 7

3 Propagation: The axillary branches that arise from the stem which is very close to the surface of the ground and break off from the parent plant that develops new plants. B.9. Sucker Sucker is a creeping, slender, short, lateral adventitious shoot arise from the underground part of stem. It grows obliquely upwards and gives rise to a leafy shoot or new plant. The internodes are short. The sucker strikes roots at the base either before it separates from the mother plant. Examples: Dagger plant, Cherry blossom, Creeping thistle, Chrysanthemum, Ligustrum, Peppermint, Rose, Tree of Heaven etc. Propagation: Suckers are usually dug during the dormant season and detached from the mother plants for multiplication. B.10. Tuber A much enlarged portion of an underground stem provided with buds on the sides and tip. It grows horizontally and swells up at the apex due to accumulation of food. They do not have basal plate but they have nodes and internodes. Eyes present at the nodes consist of scaly leaf with an axillary bud. Examples: Caladium, Jerusalem artichoke,wood sorrel etc. Propagation: Propagation can be done either by planting the whole tuber or cutting them into pieces containing one or more eyes. Each piece with eye is able to form new plant. B.11. Tuberous root Tuberous root is a thick, fleshy underground modified root that stored food. Roots are swollen at the centre and tapered towards the both ends. They do not have nodes, internodes and axillary buds. It produces a number of adventitious shoot called slips. Examples: Asparagus, Begonia, Dahlia, Mirabilis, Ruellia etc. Propagation: The tuberous root should not be divided in storage but should be divided into sections with eyes during planting. Page 3 of 7

4 Fig. Bulb of Tuberose Axil Bulbil Fig. Bulbil of Tiger lily Page 4 of 7

5 Flowering shoot New bud Leaf base Basal plate Node Roots Fig. Corm of Gladiolus Crown Fig. Crown of Day lily Offshoot Fig. Offshoot of Dendrobium Page 5 of 7

6 Fig. Rhizome of Iris Leaf Runner Node Roots Fig. Runner of Wood sorrel Stolon Aerial leaf Fig. Stolon of Colocasia Page 6 of 7

7 Fig. Sucker of Chrysanthemum Fig. Preparation of Caladium tuber for planting Distal end Portion of crown Proximal end Fig. Tuberous root of Dahlia Page 7 of 7