Plant Tissues

• principal parts of a flowering plants ; root, stem, leaf, sexual reproductive structure
• root - part of plant axis, found beneath the surface of soil
• primary function of root is absorption of water and minerals
• secondary function of root is conduction and storage
• stem - continuation of plant's axis
• primary function of stem is conduction of water and minerals from root to other of the plants, or from leaves to the rest of the plant
• stem is involved in production and support of leaves
• stem stores food materials and may even make food if they are green (chlorophyllous)
• some stems are developed underground like white potato
• tuber, modified portion of underground stem
• leaves - outgrowth of stem, some may be flat, thin, needle-like, or scale-like
• chlorophyll is merely masked by an abundance of accessory pigments
• function of leaves is closely correlated w/ the presence of chlorophyll
• sexual reproductive structure is concerned w/ sexual reproduction and production of seeds
• flowers and cones are continuation of the stem
• growth and development are influenced by both envrionment and inherited characteristic
• annuals - grow for 1 season only, producing their seeds
• biennials - grow vegetatively during the 1st season and do not produce seeds until 2nd year
• perennials - grow for several years, producing crop of seeds each year after the first years
• Sequoiadendron giganteum - tree that is a hundred years old found in california. classified as perennials
• tissue - group of cells that perform essentially the same function
• tissues are organized into functional/structural unit
• tissues are subdivided into meristematic and permanent types
• meristematic is also known as embryonic tissue
• meristematic - cells are actively dividing and new cells are continually being produced. no differentiation of cells
• meristematic cells are destined to enlarge and develope into specialized cells. but some remains and divide repeatedly, these are initials and serve to perpetuate meristems
• meristematic is consist of apical meristem, lateral meristem, intercalary meristem
• apical meristem cells are isodiametric which means they are equal in terms of diameter
• apical meristem appears to be cubical
• apical meristem are located at tips of the roots and stems (shoots and roots)
• apical meristem are immature cells w/ thin walls, they have no 2ndary layers
• protoplast and vacuoles are non-existent or appears to be small in apical meristem
• root tip - used for observing mitosis in lab (10-15%)
• 3 primary meristems develope from each apical meristem

  • protoderm
  • ground meristem
  • procambium
• lateral meristem increase the girth/dm of plant
• lateral meristem are found along sides of some roots and stem
• 2 types of lateral meristems are found in dicot plants:

  • vascular cambium
  • cork cambium
• vascular cambium - thin cylindrical sheath between bark and wood
• 2 types of thin-walled, highly vacuolated cells in vascular cambium

  • fusiform initials
  • ray initials
• fusiform initials - vertically elongated cells w/ tapering ends