Module 1 : APPLICATIONS OF PLANT BIOTECHNOLOGY IN CROP IMPROVEMENT

Lecture 4 : Plant Tissue Culture Techniques

 

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I. Quantitative Improvement

II. Qualitative Improvement

The above techniques are discussed in detail in subsequent chapters.

 

2.  Micropropagation

Growing any part of the plant (explants) like, cells, tissues and organs, in an artificial medium under controlled conditions (aseptic conditions) for obtaining large scale plant propagation is called micropropagation. The basic concept of micropropagation is the plasticity, totipotency, differentiation, dedifferentiation and redifferentiation, which provide the better understanding of the plant cell culture and regeneration. Plants, due to their long life span, have the ability to withhold the extremes of conditions unlike animals. The plasticity allows plants to alter their metabolism, growth and development to best suit their environment. When plant cells and tissues are cultured in vitro , they generally exhibit a very high degree of plasticity, which allows one type of tissue or organ to be initiated from another type. Hence, whole plants can be subsequently regenerated and this regenerated whole plant has the capability to express the total genetic potential of the parent plant. This is unique feature of plant cells and is not seen in animals. Unlike animals, where differentiation is generally irreversible, in plants even highly mature and differentiated cells retain the ability to regress to a meristematic state as long as they have an intact membrane system and a viable nucleus. However, sieve tube elements and xylem elements do not divide any more where the nuclei have started to disintegrate, According to Gautheret (1966) the degree of regression a cell can undergo would depend on the cytological and physiological state of the cell. The meristematic tissues are differentiated into simple or complex tissues called differentiation. Reversion of mature tissues into meristematic state leading to the formation of callus is called dedifferentiation. The ability of callus to develop into shoots or roots or embryoid is called redifferentiation. The inherent potentiality of a plant cell to give rise to entire plant and its capacity is often retained even after the cell has undergone final differentiation in the plant system is described as cellular totipotency.