Plant Cells and Tissues

• Plant


  Any multicellular eukaryotic life-form characterized by: Photosynthetic nutrition, Cells with cellulose walls, Absence of organs of locomotion, Absence of nervous systems

  
• Plant Cell

  • Photosynthetic nutrition
  • Cellulose cell walls
  • Stationary existence
  • No nervous system
• Parenchyma Cells


  • Thin-walled cells that make up the inside tissues of non-woody parts of plants in stems, roots, and leaves
  • Typical plant cell as they are not specialized in function
  • Functions include storage, photosynthesis, and as bulk ground and vascular tissues
  • Plant metabolism primarily takes place in these cells
  • Remain alive at maturity
  • Compose middle layer of leaves and inner/outer layers of stems and roots
  • Soft tissues of fruits are also made from parenchyma cells

  
• Collenchyma Cells


  • Support the structure of plant tissues, especially in growing areas like shoots and leaves
  • Have thin primary cell wall with some secondary thickening
  • Elongated cells with thick walls, main functions are support and structure especially in young plants

  
• Sclerenchyma Cells


  • Principal cells that support the structure of plants
  • Cell walls composed of cellulose and lignin
  • Lignin is the hardening agent that gives them rigidity
  • Unlike collenchyma, sclerenchyma cells are dead at maturity
  • Have a support function but are much more rigid than collenchyma cells
  • Thick and come in many shapes

  
• Meristematic Cells


  • Plant cells that divide and create new cells
  • Their reproduction contributes to the physical growth of plants
• Plant Tissues


  • Vascular Tissues
  • Dermal Tissues
  • Ground Tissue
  • Meristematic Tissue

  
• Vascular Tissues


  • Primary tissues responsible for transporting nutrients and water
  • Found only in vascular plants (tracheophytes) due to lignified tissues
• Vascular Tissues


  • Xylem
  • Phloem

  
• Xylem


  • Transports water from roots to stem, leaves, and buds
  • Contains tracheids and vessel elements
• Tracheids


  Long, narrow cells whose ends overlap, with small holes between to allow vertical water movement and small pits for lateral water movement
• Vessel Elements


  Shorter but wider cells, stacked on top of each other, water passes through their cell walls
• Phloem


  Carries the plant's stored carbohydrates to where they are needed, contains sieve elements
• Sieve Elements


  Functional when living, different from tracheids or vessel elements
• Dermal Tissues


  Serve as the outer protective layer of plants, like the skin
• Dermal Tissues

  • Epidermis
  • Periderm

  
• Epidermis


  Single layer of tightly packed cells that covers and protects the plant
• Periderm


  Multi-layered dermal tissue also called bark, contains cork cells, phelloderm, and cork cambium

  
• Cork Cells (Phellem)


  Nonliving cells that cover the outside of stems and roots to protect and insulate
• Phelloderm


  Can contain chlorophyll and function in defense
• Cork Cambium (Phellogen)


  Produces cork, a tough protective material
• Ground Tissue


  Makes up the plant but is neither vascular nor dermal tissue, found inside and outside the vascular tissue ring in the plant stem

  
• Meristematic Tissue


  • Collection of young cells which continuously reproduce through division
  • Found at the apices of root and shoot, embedded in vascular tissues, contribute to increase in girth size of roots and stems
• Types of Meristematic Tissue

  • Apical Meristem
  • Lateral Meristem
  • Intercalary Meristem

  
• Apical Meristem


  Cells found at the growing regions of root and shoot, contribute to increase in length
• Lateral Meristem


  Cells found in the vascular tissues, contribute to increase in thickness of a plant part

  
• Intercalary Meristem


  Cells found in regions between mature tissues, such as at the base of leaves or internodes of grasses

  
• Some Specialized Cells in Plants

  • Guard Cells
  • Root Hairs
  • Tracheids
  • Palisade Cells (Leaf Cells)
• Guard Cells


  Found in leaves, surround and control the opening and closure of stomata in response to changes in temperature and water scarcity
• Root Hairs


  Part of the dermal tissue of roots, add to the surface area and increase absorptive capacity
• Tracheids


  Elongated cells in the xylem that aid in transporting water and nutrients from roots to other parts of the plant
• Palisade Cells (Leaf Cells)


  Cells designed for photosynthesis, contain chloroplasts with chlorophyll that absorb light energy from the sun