**1. Introduction**

Plant tissue culture is a technique used to propagate plants in vitro (in test tube) under sterile conditions, often to produce clones of a plant. During the last three decades, plant cell, tissue, and organ culture have developed rapidly and become a major biotechnology tool in agriculture, horticulture, forestry, and industry. Many problems in conventional breeding techniques were solved via tissue culture techniques.

In nature, there are a variety forms of plants either seed plants for example, trees, herbs, grasses, or flowering plants for example, fruit-bearing trees. Plants exhibit the basic morphological for example, root, stem and leaves. However, they are vary with differences in cells and tissues, and their topography.

In tissue culture, the term 'culture' refers to the fragments of plants that are grown in nutrient media. There are several types of cultures, which are cell culture, tissue culture, organ culture, explant culture, and protoplast culture. Explant is the excised fragment of plants that is transferred into nutrient media. There are many types of explants, it can be roots, stems, leaves, seeds, fruits, and flowers.

The role of explant is to initiate culture in a nutrient media, provided that they must be able to de-differentiate into totipotent cells.

The term 'Tissue Culture' or micropropagation is the technique to propagate plants under sterile conditions, often to produce clones of a plant. The cultured of explant on a solid medium produces mass of protoplasmic cells which later be induced to become a complete plant. However, in organ culture, for example, excised roots, the cultured explant (plant material) maintains its morphology identity, more or less, similar with the same physiology as in vitro of the parent plants. Plant organs are referred to part of plants that possess vascular tissues such as root, shoot, and leaves. Embryo is an independent structure and does not have vascular supply, thus, embryo is not supposed to be the plant organ.
