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plant structure and function ch22sec1,2,3 MASHAEL ALHAIDAR - Coggle…

- - - - Action : stimulate cell division and affect seed growth and elongation
      - Pathway : transport through vascular tissue to reach the target tissue
      - Dwarf plants lack gibberellins production or gibberellins receptor proteins.
      - Human use gibberellins by spraying it on plants to increase plant height
  - - - It is the only gas hormone
      - Action: affects the ripening of fruit, senescence of leaves ( aging of leaves leading to color change )
      - Mechanism : weakening cell walls of unripe fruits and causing the break down of complex carbs into simpler ones giving sweetness to the fruit.
      - Path way : travels through the phloem as well as the space between the cells
  - - - -Cytokinins : induce growth in rapidly dividing cells
      - Pathway : travel to other cells through the xylem
      - Promote cell division
      - Influenced by the presence of auxin
      - Mechanism ; stimulating the production of proteins needed for mitosis and cytokinins
- - - - The vascular cambium is a thin cylinder of meristematic tissue . can run the entire length of roots or stem.
      - 1-the crock cambium . Produces cells that form a protective outside layer on stems and roots
      - Dermal tissue ( skin) the epidermis is the outer layer.
      - 2-Epidermal cells resemble pieces of a jisaw puzzle with interlocking ridges and dips. Epidermis has several adaptations to protect the plant and prevent water loss. It changes in the shape of guard cells ( 2 cells that form stomata) that result in the opening and closing of stomata to prevent water loss. There is also root hairs that increases area of absorption
      - 3-Vascular tissue
        
        1- Xylem carries water and dissolved minerals up hem stem to the leaves
        2-Phloem transports materials such as sugars and amino acids up and down the plant
        phloem is consist of 2 types pf cells , 1- Sieve tube members contain cytoplasm but lack nuclei and ribosomes when mature. 2-Companion ells occur next to sieve tube cells and have a nucleus.
      - 4- Ground tissue , plants tissues that are not meristematic , dermal or vascular tissue.
        consists parenchyma , collenchyma and sclerenchyma cells.
        Functions include photosynthesis , storage and support.
- - - - .
        
        Phototropism : growth to light
        
        Gravitropism: growth to gravity
        
        Thigmotropism : growth to mechanical stimuli , such as contact with an object organism or wind.
- - - - The inner boundary of the context is a layer called the endodermis
      - Each endoderm is encircled by a waterproof strip called Casparian strip
      - The Caspariam strip forces water and substances to pass through the endodermal cells instead of around them
      - Next to the endodermis theres a root called pericycle , which produces lateral roots.
  - - - Herbaceous stems are soft , flexible and capable of photosynthesis
      - Woody stems are, rigid and fibrous and NOT able to make photosynthesis
      - Bark stems are , tough , cocky tissue that can protect the stem rom physical damage and insect invasion
    - - Main functions
      - 1support plan leaves and reproductive structures.
      - 2- Transport water and nutrients
    - - Apical meristem produces cells that increase the length of a stem.
      - Vascular cambium produces additional cells to increase stem diameter
      - Apical meristem and the vascular cambium form annual grown rings in some plants especially trees which can be used to know the age of the tree
    - - Stems adaptations that helps a plant to survive , stores excess food , withstand drought cold , or heat. Some plants have underground stems ( tubers , bulbs, rhizomes)
        
        Rhizome , ex : Iris , its function as a food storage and Asexual reproduction
        
        Runner ( stolons) , ex : spider plant , it function Asexual reproduction
        
        tuber , ex : potato , functions as food storage
- - - - -In cacti , leaves have been modified into spines to prevent predation by animals.
      - -Pitcher plants modify leaves into cylinders that fill with water and trap insects
      - Some leaves produce toxic chemicals to prevent predation