Plant Developmental Biology: Endosymbiosis and Evolution

Endosymbiosis Theory

• Eukaryotic cell engulfs bacterium, providing protection and carbon compounds, while bacterium supplies ATP.
• This relationship led to the evolution of mitochondria and chloroplasts.

Evolution of Plant Development

• Multi-cellular green organisms developed from eukaryotic plants' ancestors.
• Examples of endosymbiosis in nature include secondary endosymbiosis and serial ingestion of photosynthetic bacteria.
• Gene transfer among genomes and evolution of plastids like chloroplasts occurred.
• Evidence of bacterial descent is seen in the position of mitochondria and plastid DNA in phylogenetic trees and DNA sequences.
• Evolution of plants from green algae as plant ancestors, adapting to life on land with challenges and advantages.

Plant Structure and Function

• Different plant structures, such as vascular spores, have unique functions.
• Evolutionary timeline of plant types on land include key developments.

Growth and Development

• Plant growth, development, and differentiation are influenced by factors like cell number and weight.
• Parameters to measure plant growth include cell number and weight.
• Types of growth:
  • Primary Growth: Length increase from mitotic division at root and shoot apex.
  • Secondary Growth: Diameter increase from secondary meristem.
  • Unlimited/Indeterminate Growth: Continuous growth of root and shoot system.
  • Limited/Determinate Growth: Leaves, fruits, and flowers stop growing after a certain size.

Meristematic Tissues

• Shoot apical meristem and root apical meristem are types of meristematic tissues.
• Meristems are regions with unspecialized cells for continuous division.
• Characteristics of meristematic tissues include self-renewal quality, small and few vacuoles, dense protoplasm, and healing wounded plant tissues.

Classification of Meristem

• Classification based on origin and position include apical, intercalary, and lateral meristem.
• Secondary meristem is derived from primary meristem, with vascular cambium and cork cambium forming meristematic tissues.

Cell Types and Functions

• Examples include sclerenchyma, phloem, collenchyma, parenchyma, transfer cells, etc., which have roles in support, transport, and metabolism.

Meristem Position

• Apical meristem is located at root and shoot tips for primary growth.
• Lateral meristems are responsible for secondary growth in stems, with vascular cambium and cork cambium contributing to width and girth.

Differentiation and Redifferentiation

• Differentiation involves qualitative changes in plants for specialized functions.
• Process where genetically identical cells become specialized.
• Redifferentiation/transdifferentiation involves dedifferentiation, stem cell-like state, and differentiation, with factors like auxin, cellulase, and cell death playing roles.