Plant Biotechnology and Tissue Culture

Plant Biotechnology

• Plant biotechnology involves using science and technology to alter plants or their parts for knowledge, goods, and services
• It encompasses techniques for screening and genetic manipulation of plants
• Traditional breeding techniques were used in the past: selection, hybridization (crossing)
• Plant tissue culture techniques are frequently used today

Plant Tissue Culture

• Uses isolated parts of plants called explants
• Explants are cultured on a nutrient medium, which replaces the environment they were originally in
• Cultures are usually maintained in aseptic conditions. Exceptions include experiments on phytopathology and co-culture studies
• The concept of plant tissue culture is based on totipotency and plasticity
  • Totipotency: any plant cell can become a whole plant with nourishment
  • Plasticity: the ability of an organism to change its phenotype in response to different environments

Brief History of Plant Tissue Culture

• 1756: Henri Louis observed that cells form at wound sites in elm plants
• 1878: Vöchting observed that the upper part of a shoot produces buds and the lower part produces callus and roots
• 1902: Gottlieb Haberlandt proposed the principle of totipotency
• 1922: Kotte and Robbins cultured root and stem tips
• 1926: Fritz Went discovered the first plant growth hormone, indole acetic acid
• 1939: Gautheret and Nobecourt worked independently on callus cultures
• 1946: Ernest Ball produced plants from shoot tip culture
• 1962: Murashige and Skoog optimized a medium for plant growth in vitro
• 1964: Guha and Maheshwari produced haploid plants from anther culture
• 1970: Power et. al. fused isolated plant protoplasts

Importance of Plant Tissue Culture

• Rapid Clonal Propagation: Produces many genetically identical plants from a single parent plant. Useful for valuable or rare species
• Year-Round Propagation: Tissue culture is not affected by seasons, unlike traditional methods
• Disease-Free Plants: Starts with sterile explants, which are free from diseases, pests, and pathogens
• Preservation of Rare or Endangered Species: Helps conserve and grow threatened species
• Genetic Modification: Introduces desired traits such as pest and disease resistance, environmental stress tolerance
• Production of Secondary Metabolites: Produces pharmaceuticals, essential oils, and other valuable plant compounds
• Storage and Banking of Genetic Material: Long-term storage of seeds, embryos, and meristems to preserve genetic diversity

Disadvantages of Plant Tissue Culture

• Labor-Intensive: Requires technical expertise and labor, making it expensive
• Genetic Uniformity: Can lead to lack of diversity, making plants susceptible to new pests and diseases
• Risk of Somaclonal Variation: Genetic variations that can occur in tissue-cultured plants, resulting in unexpected traits or mutations

Rules for Explant Selection

• Select superior-quality, disease-free plants and explant types

• Young leaves (in vitro leaves) are used for direct or indirect organogenesis or somatic embryogenesis

• Other explants, except seeds, shoot tips, or nodal segments, are avoided, as the tissue is highly differentiated. Forcing it to dedifferentiate and redifferentiate can cause physiological stress.

Types of Plant Tissue Cultures

• Organized Structure Culture:
  • Meristem Culture: Excised shoot apices with apical meristematic dome, with or without leaf primordia
  • Shoot Tip Culture: Excised shoot tips or buds larger than shoot apices. Used to establish meristem cultures, typically with several leaf primordia
  • Node Culture: Separate lateral buds with a small piece of stem tissue. Can have single or multiple nodes
  • Isolated Root Culture: Growth of roots unconnected to shoots. Might obtain a branched root system
  • Embryo Culture: Fertilized or unfertilized zygotic (seed) embryos are dissected out of seeds or fruits and cultured until they become seedlings
• Unorganized Structure Culture
  • Callus Culture: Growth of unorganized cell masses from plant organs, tissues, or previously cultured cells
  • Suspension Cell Culture: Populations of plant cells and small cell clumps dispersed in an agitated, aerated, liquid medium
  • Protoplast Culture: Cultures of plant cells without a cell wall
  • Anther Culture: Cultures of complete anthers containing immature pollen microspores. Aim is to obtain haploid plants through somatic embryo formation

Explore the fascinating world of plant biotechnology, focusing on the techniques and history of plant tissue culture. Learn about the critical concepts of totipotency and plasticity that are fundamental to the manipulation of plant cells. This quiz will challenge your understanding of how science shapes our interaction with plants.