·         1.2.  Terms commonly used in plant tissue culture

Plasticity and totipotency: Plants due to their long-life cycle and lack of mobility have developed greater capacity to survive extreme conditions. Many of the processes involved in plant growth and development adapt to environmental conditions. This plasticity allows plants to alter their metabolism, growth and development to best suit their environment. Plants also have, in many cases, the ability to regenerate lost organs (roots, shoots etc.). Cell division can be induced from almost all plant tissues. When plant cells and tissues are cultured in vitro, they generally exhibit a very high degree of plasticity, which allows one type of tissues or organs to be initiated from another type under the influence of chemical stimuli. In this way, whole plants can be subsequently regenerated. For example, embryos may be developed in vitro from somatic cells and haploid cells, as well as from normal zygote and all these, in turn, could develop into whole plants.

Totipotency is the potentiality or property of a cell to produce a whole organism or whole parent plant in the presence of correct physical and chemical stimulus.

Recalcitrant: The opposite of totipotency is recalcitrant. An explant is said to be recalcitrant if it is difficult to give rise to organism or plant.

Explant: A plant organ or piece of tissue used to initiate a culture.

Culture: Growing cells, tissues, plant organs, or whole plants in nutrient medium, under aseptic conditions e.g. cell culture, embryo culture, shoot-tip culture, anther culture.

Contaminants: In tissue culture it refers to the micro-organisms (Bacteria, Fungi), which may inhibit the growth of cells or tissues in culture.

Node: A region on the stem from which a leaf bearing an axillary bud arises.

Morphogenesis: The anatomical and physiological events involved in the growth and development of an organism resulting in the formation of its characteristic organ and structures, or in regeneration.

Meristem: A localized group of actively dividing cells, from which permanent tissue system i.e. root, shoot, leaf and flower are derived. Apical meristem is located at the apices of main and lateral shoots.

Meristematic: having the characteristics of a meristem, especially high mitotic activity.

Meristemoid: A localized group of meristematic cells that arise in the callus and may give rise to roots and or shoots.

Regeneration: In tissue culture, a morphogenetic response that results in the formation of new organs, embryos or whole plants from cultured explants.

Dedifferentiation: The phenomenon of mature cells reverting to meristematic state to produce callus is dedifferentiation. Dedifferentition is possible because the non-dividing quiescent cells of the explant, when grown in a suitable culture medium revert to meristematic state.

Redifferentiation: The ability of the callus cells to differentiate into a plant organ or a whole plant is regarded as redifferentiation.