Class notes

• Atom Molecule Cells Traces Organs Systems

  • Ecosystem
  • Community
  • Population
  • aganiam
• Menstematic

  Cells that can divide
• Merisicmatic

  Cell division, growth
• Epidermal

  Protect, absorb H₂O, change gases
• Parenchyma

  Store, package
• Selerenchyma

  Strengthen, Support, shape
• Collenchyma

  Strengthen, protect
• Chlorenchyma

  Photosynthesis, has chloroplasts
• Xylem

  Transport H₂O + minerals, strengthen, support
• Phloem

  Transport manufactured food
• Companion Cells

  Help sieve tubes
• Location of Meristematic Tissue

  • Tips of roots & stems (apical meristem)
  • Stems of woody trees (lateral meristem)
• Meristematic Tissue

  • Thin walled, tightly packed, no intercellular spaces, single large nucleus, dense cytoplasm, small/no vacuole, undifferentiated cells that are dividing cells, can then differentiate continuously
• Function of Meristematic Tissue

  Makes new cells for growth by cell division, some remain meristematic while others differentiate into permanent tissue
• Epidermis

  First layer on the outside of plants, single layer of tightly packed cells with no intercellular spaces, often box shaped with thick outer wall to protect
• Epidermis

  • Protects inner tissues, root hairs increase surface area for absorption, cuticle prevents excess water loss, stomata allow gas exchange, guard cells control opening and closing of stomata
• Parenchyma

  Forms bulk of plant tissues, scattered throughout, stores food and water, allows gases/water/minerals to move, contains chloroplasts for photosynthesis
• Parenchyma

  • Thin-walled, large vacuoles, intercellular air spaces
• Collenchyma

  On the perimeter of stem and root, provides protection, strengthening, flexible support
• Collenchyma

  • Unevenly thickened with cellulose, mainly in the corners
• Sclerenchyma

  Around the vascular bundles, provides protection, strength and support
• Sclerenchyma

  • Made up of fibres and stone cells, cell walls unevenly thickened with lignin, narrow lumen
• Xylem

  Consists of elongated, non-living cells with lignin-strengthened walls, forms long continuous tubes for transport of water and dissolved solutes
• Phloem

  Consists of sieve tubes and companion cells, transports dissolved organic nutrients like glucose
• Meristematic cells are small, spherical or polygonal in shape, have very small or no vacuoles, and have a large amount of cytoplasm and a large nucleus
• The epidermis is a layer of cells covering the entire surface of the plant, it is thin and transparent
• Epidermal tissues have abundant trichomes (tiny hairs) projecting from the surface, root hairs are elongations of epidermal cells in the root
• Epidermal tissues in leaves are covered with a waxy cuticle, and contain guard cells with chloroplasts
• Some plant epidermal cells can secrete poisonous or bad-tasting substances
• Parenchyma cells have thin walls, intercellular spaces, and large central vacuoles
• Specialised parenchyma cells called chlorenchyma in plant leaves contain chloroplasts and perform photosynthesis
• Some parenchyma cells retain the ability to divide
• Collenchyma cells are spherical, oval or polygonal in shape with no intercellular spaces, the corners of the cell walls are thickened with cellulose and pectin
• Collenchyma provides mechanical strength and flexibility to allow the plant to bend in the wind
• Sclerenchyma cells are dead, with lignified secondary cell walls, sclereids have strong walls filling nearly the entire cell volume
• Sclerenchyma provides mechanical strength and structural support, the lignin gives 'wire-like' strength to prevent tearing
• Sclerenchyma structures are used to protect other cells, and provide the hardness of fruits like pears
• Xylem consists of elongated, non-living cells with lignin-strengthened walls, forming long continuous tubes to transport water and dissolved solutes
• Phloem consists of sieve tubes and companion cells, transporting dissolved organic nutrients like glucose
• Companion cells contain nuclei and control the functions of the sieve tubes, which lack organelles