Definitions [2]
Define the following:
Meristematic tissue
Meristematic tissue is a group of cells that constantly divide and produce cells indefinitely throughout the life of the plant.
Define the following:
Permanent tissue
Permanent tissue refers to a group of cells which temporarily or permanently cease to divide and thus assume permanent form and function
Key Points
Key Points: Meristems or Meristematic Tissues
- Meristematic tissue consists of cells that can divide and is restricted to specialised regions of the plant.
- Apical meristem is found at the root and shoot tips, is a primary meristem and increases the length of the plant.
- Intercalary meristem is found between mature tissues, is a primary meristem and helps form branches and flowers.
- Lateral meristem is found in mature regions, is a secondary meristem and is responsible for secondary growth (e.g. vascular cambium, cork cambium).
- Axillary bud is present in the axils of leaves and is responsible for forming branches or flowers.
Key Points: Tissue System
- Tissue variation in plants depends on their location in the plant body, and the structure and function of each tissue is related to where it is found.
- Plants have three main tissue systems: epidermal tissue system, ground (fundamental) tissue system and vascular (conducting) tissue system.
- These three systems are classified based on their structure and location, and each serves a specific purpose in plant anatomy.
Key Points: Epidermal Tissue System
- Epidermal tissue is the outermost covering of the plant body, made up of epidermal cells, stomata, trichomes and root hairs.
- Epidermis is a single layer of compactly arranged parenchymatous cells covered with a waxy cuticle (absent in roots) to prevent water loss.
- Stomata regulate transpiration and gaseous exchange; each stoma has two bean-shaped guard cells (dumb-bell shaped in grasses).
- Stomatal apparatus = stomatal aperture + guard cells + subsidiary cells.
- Root hairs are unicellular extensions of epidermal cells that absorb water and minerals from the soil.
- Trichomes are stem hairs that may be branched, unbranched or secretory, and help prevent water loss.
Key Points: Vascular Tissue System
- Vascular bundles = Xylem + Phloem together, and they form the vascular tissue system.
- Open vascular bundles are found in dicot stems where cambium is present between xylem and phloem, allowing the formation of secondary tissues.
- Closed vascular bundles are found in monocot stems where cambium is absent, so no secondary growth takes place.
- Radial bundles have xylem and phloem placed on different radii (alternating with each other) and are found in roots.
- Conjoint bundles have xylem and phloem on the same radius, with phloem always on the outer side of xylem, and are found in stems and leaves.
