Stomatal count and the Vascular tissues

• Stoma


  A pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spaces of the leaf and the atmosphere

  
• Functions of the stomata

  • Gaseous exchange
  • Transpiration and removal of excess water
  • Stomatal closure at night prevents water from escaping
  • Maintains moisture balance
  • Facilitates carbon dioxide uptake and oxygen release during photosynthesis
• Subsidiary cells


  • Surround the guard cells
  • Accessory cells to guard cells
  • Found in the epidermis of plants
  • Protect epidermal cells when guard cells expand during stomatal opening
• Types of stomata


  • Anomocytic
  • Anisocytic
  • Diacytic
  • Paracytic
  • Gramineous
• Anomocytic stomata


  • Surrounded by epidermal cells, which have a fixed shape and size
  • Appear to be embedded in epidermal cells
  • No definite number and arrangement of cells surrounding the stomata

  
• Anisocytic stomata


  Surrounded by three subsidiary cells having unequal sizes, one is smaller compared to the other two

  
• Diacytic stomata


  Surrounded by a pair of subsidiary cells that are perpendicular to the guard cell
• Paracytic stomata


  Continuously surrounded by two subsidiaries, which are arranged parallel to the stomatal pore and the guard cells
• Gramineous stomata


  • Each stoma possesses two guard cells, which are shaped like dumbbells
  • Subsidiary cells are parallel to the guard cells
  • Guard cells are found narrow in the middle and wider at the ends
• The average number of stomata is about 300 per square mm of the leaf surface

  
• Dicots have more stomata on the lower surface, whereas monocots have stomata distributed equally on both the surfaces of leaves

  
• Vascular tissues


  • Complex conducting tissues in higher plants that are made up of different types of cells and elements
  • Two main components: Xylem and Phloem
  • Responsible for the transport of water and nutrients in the plants

  
• Vascular tissues in monocot stems

  • Vascular bundles are randomly scattered throughout the ground tissue
  • Vascular bundles are closed and they lack cambium
  • Cambium is the only meristematic tissue in the stem and the root that can trigger the secondary growth

  
• Vascular tissues in dicot stems

  • Vascular bundles are arranged in a ring toward the stem periphery
  • This arrangement is essential for a phenomenon called secondary growth
• Factors that stimulate stomatal closing and opening

  • Hormone, ABA and JA
  • Light quality and intensity
  • Air humidity
  • Atmospheric CO2 concentration
  • Biotic and abiotic stresses
• Light-mediated signaling and metabolic changes coordinate stomatal movements
• three surrounding cells differ in size. This arrangement aids in regulating gas exchange and water loss, contributing to plant adaptation to various environmental conditions.

  A) Anisocytic

  
• In this arrangement, the surrounding cells of the stomata are irregular in shape and size, lacking any specific pattern or arrangement.

  A) anomocytic

  
• refers to a specific type of stomatal complex found in plant leaves. In this stomata, two subsidiary cells surround each stoma, forming a distinct pattern. This arrangement aids in regulating gas exchange and controlling water loss through transpiration, contributing to the plant's adaptation to its environment.

  A) diacytic

  
• is a type of stomatal complex found in the epidermis of plant leaves. In this stomata, the guard cells are surrounded by two subsidiary cells parallel to the stomatal pore. This arrangement helps regulate gas exchange and water vapor loss from the leaf surface.

  A) paracytic

  
• the guard cells are surrounded by radial arrangements of subsidiary cells, resembling rays extending outward from the stomatal pore.

  A) Actinocytic

  
• such as grasses, typically have brachyparacytic stomata. These stomata feature guard cells surrounded by subsidiary cells parallel to the stomatal pore, with shorter subsidiary cells compared to typical paracytic stomata.

  A) Gramineous

  
• are a type of stomatal complex found in certain plant species. In this stomata, the guard cells are surrounded by four subsidiary cells, forming a distinctive pattern. This arrangement facilitates gas exchange and regulates water vapor loss from the leaf surface.

  A) tetracytic

  
• stoma

  • a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spaces of the leaf and the atmosphere
• functions of the stomata

  • gaseous exchange- stomatal opening and closure help in the gaseous exchange between the plant and surrounding
  • it helps in transpiration and removal of excess water in the form of water vapour
  • Stomatal closure at night prevents water from escaping through pores
  • It maintains the moisture balance according to weather by opening and closing
  • Stomata facilitate carbon dioxide uptake and release of oxygen during the process of photosynthesis
• abaxial (lower) leaf epidermis of a Tradescantia pallida leaf, showing stomata and guard cells

  
• stomata open

  A) epidermal cell

  B) chloroplast

  C) inner thick wall

  D) outer thick wall

  E) vacuole

  F) guard cells

  G) nucleus

  H) stomatal pore

  
• stomata closed

  A) nucleus

  B) guard cells

  C) vacuole

  D) chloroplast

  
• structure of stomata

  A) epidermal cell

  B) subsidiary cell

  C) stomatal pore

  D) guard cell

  
• • the subsidiary cells surround the guard cells
  • they are the accessory cells to guard cells and are found in the epidermis of plants
  • they are present between guard cells and epidermal cells and protect epidermal cells and protect epidermal cells when the guard cells expand during stomatal opening
• Anomocytic stomata

  • surrounded by epidermal cells, which have a fixed shape and size
  • appear to be embedded in epidermal cells
  • no definite number and arrangement of cells surrounding the stomata

  
• diacytic stomata

  • surrounded by a pair of subsidiary cells that are perpendicular to the guard cell

  
• paracytic stomata

  • continuously surrounded by two subsidiaries, which are arranged parallel to the stomatal pore and the guard cells

  
• Gramineous stomata

  • each stoma possesses two guard cells, which are shaped like dumbbells
  • subsidiary cells are parallel to the guard cells
  • guard cells are found narrow in the middle and wider at the ends

  
• maize belongs to the grass family (Gramineae) and the epidermis of these plants is characterized by elongated cells with undulating cell walls. The stomata are oriented parallel and have 2 subsidiary cells

  
• Phloem transports sugars produced through photosynthesis from leaves to other parts of the plant
• Xylem transports water from roots to leaves and other parts of the plant
• stomatal shapes in three different monocot plants with indication of guard cells (1) and subsidiary cells (2). A: anomocytic, Dracaena B: paracytic, maize. C: tetracytic, Tradescantia

  
• dicots have more stomata on the lower surface, whereas monocots have stomata distributed equally on both the surfaces of leaves
• vascular tissues

  • complex conducting tissues in higher plants that are made up of different types of cells and elements
  • two main components: xylem and phloem
  • these tissues are responsible for the transport of water and nutrients in the plants