In angiosperms, the normal method of reproduction is by seed formation involving meiosis and fertilization. This kind of reproduction is referred to as sexual reproduction. In several instances, angiosperms plants manage to reproduce by methods which do not involve meiosis and fertilization.
Such a method of reproduction is called asexual reproduction or apomixis. In this method of reproduction, all divisions are mitotic and hence the offsprings produced are genetically similar to the parent plant.
Asexual reproduction can be divided into two types on the basis of the plant part involved in carrying out multiplication:
(i) Agamospermy:
Where a seed formed without involving meiosis and fertilization serves as a propagule.
(ii)Vegetative propagation:
Where a vegetative part of the plant such as stem, root, leaf etc. serves as a propagule. Vegetative Propagation can be defined as the formation of new individuals from any vegetative part of the plant body. In this method of reproduction, a portion of the vegetative part of the plant is separated or gets detached from the mother plant and develops into a new and independent plant.
Several plant species produce modified structures especially for their multiplication and perpetuation in nature. At the same time, man has developed several methods for multiplication of economically useful plants by artificial vegetative propagation.
1. Mound layering:
In this case, a branch near the ground is bent down, a ring of bark (2.5 – 5.0 cm) is removed and this portion is pushed in the soft moist soil. It is done in such a way that the tip of the branch remains above ground. In a few days or weeks, the covered part of a stem strikes adventitious roots. At this stage, the branch is cut off from the parent plant and grown separately. Common examples are jasmine, grape – wine, lemon, rose etc.
2. Air layering or Gootee:
This technique is employed in trees with thick branches and which can not be bent easily. During early rains, a healthy and woody branch is selected and is girdled (i.e. a ring of bark, 2.5 – 5 cm long is sliced off). The girdled part is covered with moist moss or cotton and then covered with polythene bag or jute piece. This covered part is known as Gootee. To keep the gootee wet, an earthen pot with a minute hole at the bottom may be hanging over the gootee as shown in the diagram. Roots develop, usually, within 1 – 3 months. It is then separated from the parent plant and planted in the soil.
