Some plants can be artificially propagated by using their vegetative parts and this is called artificial vegetative propagation. Following are a few types of artificial vegetative propagation by stem, in plants.
1. Cuttings: These are short pieces of stem with 2 or 3 nodes and buds, which are cut obliquely below a node from a plant. The cuttings are embedded in soil bed with at least one node. The adventitious roots and shoots grow from buds of the portion below the soil and above the soil respectively, forming a new plant, e.g. Sugar cane, balsam, sweet potato, Hibiscus and rose. In Raspberry and black berries, root cutting are also used for artificial vegetative propagation. [Fig. 16.6]
2. Grafting: This is a technique whereby a branch from a desired variety of plant is joined to another plant with well established root system. The plant from which the branch is taken is called scion and the plant to which it is joined is called stock. The two plants involved are normally the varieties of same species e.g. oranges, lime, lemon and mango. [Fig.16.6 (b)]
Fig. 16.6 artificial vegetative propagation in plants: (A) by stem cutting, (B) by stem grafting
Take one stem cutting of rose plant with at least 6-8 inches in length and having 4-5 nods with buds.
Plant it obliquely in the soil in one pot. The pot should by well watered.
Take leaf cuttings of Bryophyllum leaf. Put 2 or3 of these cuttings on the surface of soil in the other pot. The pot should by watered regularly.
Observe after a few days and answer the following questions.
1. How long does it take for the stem cutting to develop shoots from the bud?
2. How long does it take for the adventitious bud in leaf cutting to cevelop a shoot?
3. Cloning: It is also a type of asexual reproduction in which populations of genetically identical individuals are produced from a single parent using the parent’s tissues of vegetative cell under proper laboratory conditions.
“A clone has the advantage that the good characteristics of the parent are passed as such to all the offspring. This is very useful quality of the next generation.”
There are certain plants with underground stems, which also reproduce by vegetative propagation using a small piece bearing buds, like onion bulb, corm of colocacia, rhizome of ginger or canna lily and potato tuber.
Fig. 16.7 some of the examples of underground stems