specialised cells and tissues

• meristems


  Where plants stem cells are
• Phloem is the tissue that carries the products of photosynthesis
• xylem is the tissue that carries water and mineral ions from the roots to all parts of the cell
• the phloem and xylem are vascular tissues in plants
• Plants have epidermal meristematic and vascular tissues
• epidermal tissue in plants


  Consists of flattened cells, lacks chloroplasts and forms of protective covering over leaves stems and roots and reduces water loss
• meristematic tissues divide into 3 types

  1. apical meristem
  2. lateral meristem
  3. intercalary meristem
• apical meristems are located in roots and shoots and help to increase length
• lateral meristems are located at the cambium and help increase girth
• intercalary meristems are located at the base of the leaves of internodes and helps to grow twigs into branches and help the tissue fill with cytoplasm
• dividing tissues are meristematic tissues
• non-dividing tissues are permanent tissues
• meristematic tissues grow and divide after maturity
• permanent tissues can be split into simple and complex tissues
• simple tissues

  • parenchyma
  • collenchyma
  • sclerenchyma
• parenchyma is a packaging tissue that fills spaces between other tissues they store more starch and in aquatic plants parenchyma keeps plants buoyant
• collenchyma cells have thick cell walls they strengthen vascular bundles and outer part of stems and are made of cellulose
• sclerenchyma cells have lignified walls and strengthen stems and leaf midribs
• palisade cells carry out the most photosynthesis by absorbing lots of light as they are packed with chloraplast
• palisade cells are packed together closely but with little space so air can circulate
• palisade cells have a large vacuole so that the chloroplast is positioned nearer the periphery reducing diffusion distance
• root hair cells are specialised to absorb water and mineral ions
• root hair cells have large surface area and thin surface layer