Plant Structure and Function

• Plants

  • Mosses, ferns, flowering plants, trees, conifers
  • have unique properties that distinguish them from other organisms
• Viridiplantae or Chlorobionta - monophyletic group of eukaryotic organisms which includes green algae and land plants (embryophytes) (green plants)
• APOMORPHY is a specialized trait or character that is unique to a group or species
• Cellulosic cell wall - encloses the plant cell protoplast, cellulose rigidity to the cells, acts like a cellular exoskeleton
• Specialized type of chloroplast - chlorophyll b as additional pigment, thylakoids stacked in grana o true starch storage compound.
• Green algae are a paraphyletic group, consists of:

  • Chlorophytes
  • Streptophytes
  • Charophytes
• Chlorophytes – “green algae”, exhibit a wide range of forms. Flagellated unicells with or without flagella, thalloid forms, motile and nonmotile colonies, and nonmotile filaments, sexual reproduction through the fertilization of flagellate, haploid isomorphic gametes.
• Streptophytes – non-land plant streptophytes, gave rise to land plants ▪ evolved to have a type of sexual reproduction (oogamy) where the egg becomes larger and non-flagellate
• Charophytes – “green algae”that resemble land plants
• Plasmodesmata: pores in the primary cell wall through which membranes traverse between cells.
• Embryophyta (land plants):

  • sporophyte/embryo (alternation of generation)
  • cuticle
  • parenchyma
  • antheridium
  • archegonium
• Plant Tissues - is a collection of similar cells performing an organized function for the plant
• Meristematic Tissues - a type of tissue system in plants, composed of a mass of undifferentiated cells and their primary function is to take part in the growth of plants
• Cellular characteristics (Meristem)

  • Cells usually isodiametric
  • Cells relatively smaller than in permanent tissues
  • Nucleus is darkly staining
  • Intercellular space generally absent
  • Of primary cell wall only
  • Vacuole usually absent or very small (less dense protoplasm)
  • Low metabolic activity
• Types of meristematic tissues according to origin and development:

  1. Promeristem
  2. Primary Meristem
  3. Secondary Meristem
• Promeristem: Exhibit no evidence of tissue differentiation and are presumed to be in the same physiological state as the initials
• Primary Meristem: Give rise to the mature primary tissues of the shoot and root or to the tissues of the mature organ
• Protoderm gives rise to the epidermis

  Procambium gives rise to primary vascular tissue

  Ground Meristem is the precursor of the fundamental or ground tissue system
• Secondary Meristem: initials originate from cells that have differentiated, then resumed meristematic activity
• Types of meristematic tissues according to location:

  1. Apical Meristem
  2. Lateral Meristem
  3. Intercalary Meristem
• Apical meristem: meristems that are located in the apices of main and lateral shoots and roots
• Lateral meristem: meristem arranged parallel with the sides of the axis
• Intercalary meristem: inserted or intercalated between tissues that are not meristematic
• Meristematic Tissue Types: Protoderm (epidermis), procambium (vessel elements), Ground Meristem (palisade mesophyll)
• Types of meristematic tissues according to function:

  1. Those giving rise to primary growth: primary meristem
  2. Those giving rise to secondary growth: secondary meristem
• Those giving rise to primary growth: primary meristem - initials are direct descendants of embryonic cells that never ceased to be concerned with meristematic activity
• Those giving rise to secondary growth: secondary meristem - initials originate from cells that have differentiated, then resumed meristematic activit
• Permanent Tissues - Plant tissues that are not mitotically active as they are already differentiated with specific functions such as conduction, providing mechanical support or carrying out photosynthesis etc.
• Simple permanent tissue: Composed of a single type of cell: parenchyma, collenchyma, sclerenchyma
• Complex permanent tissue: Composed of different types of cells - xylem tissue, phloem tissue
• Tissue Systems: All three basic vascular plant organs—roots, stems, and leaves— are composed of three fundamental tissue types: dermal, vascular, and ground tissue.
• Dermal Tissue System - The dermal tissue system serves as the outer protective covering of the plant.
• Dermal tissue - It forms the first line of defense against physical damage and pathogens.
• In nonwoody plants, it is usually a single tissue called the epidermis

  In woody plants, the periderm replaces the epidermis in older regions of stems and roots.
• Vascular Tissue System - The chief functions of the vascular tissue system are to facilitate the transport of materials through the plant and to provide mechanical support

  • The two types of vascular tissues are xylem and phloem.
  • The vascular tissue of a root or stem is collectively called the stele (the Greek word for “pillar”)
• Ground Tissue System - Tissues that are neither dermal nor vascular are part of the ground tissue system.
• Ground tissue is not just filler: It includes cells specialized for functions such as storage, photosynthesis, support, and short-distance transport