BIO 13- 1st LE- PLANT TISSUES

• 2 general types of Plant Tissue System: Meristematic Tissue, Permanent (0r non-meristematic) Tissue
• Meristematic Tissue- cells are found in the meristems. Cells are either undifferentiated or incompletely differentiated. They continue to divide and contribute to plant growth. Has three types: Apical Meristems, Lateral Meristems, Intercalary Meristems.

  **Meristems produce cells that quickly differentiate or specialize and become permanent tissue.**
• Apical Meristems- located at the tips of stems and roots. For length.
• Lateral Meristems- facilitate growth in thickness or girth.
• Intercalary Meristems- only in monocots, at base of leaf blades and at nodes.
• Permanent (or non-meristematic) Tissue- consists of plant cells that are no longer actively dividing.
• 2 types of Tissues: Simple Tissues and Complex Tissues
• • Simple Tissues- composed of only one type of cell.
  • Ground Tissue. 
• • Complex Tissues- composed of more than one type of cell. 
  • Dermal and Vascular Tissues.
• Three types of Tissue Systems: Ground Tissue, Dermal Tissue, and Vascular Tissue
• • Ground Tissue- includes the cortex and pith.
  • Store molecules (starch), photosynthesize (mesophyll cells), or support the plant.
• Three types of Simple Permanent Tissues under Ground Tissue Systems: Collenchyma, Parenchyma, and Sclerenchyma
• • Collenchyma- has axially elongated cells, and unevenly thickened primary cell wall (PLASTIC). Main function is the mechanical support of young stems and leaves via turgor. 
  • Frequently positioned immediately beneath the epidermis.
• Types of Collenchyma, based on pattern of thickening: Angular, Annular, Lamellar, and Lacunar
• • Angular- Collenchyma type where cell corners are differentially thickened.
• • Annular- Collenchyma type where it has uniformly thickened walls; common type.
• • Lamellar- Collenchyma type where it has a thickened inner and outer tangential wall.
• • Lacunar- Collenchyma type where it has thickening walls facing the cavity lumen.
• • Sclerenchyma- a dead supportive tissue. Consists of long sclerenchyma fibers, or short, crystal-like cells (sclereids). 
  • Has a thickened secondary wall that is rich in lignin (lignified). 
  • Main function: support of older plant organs, and also hardening different parts of plants. Mechanical support. 
  • Dead at maturity. 
  • Positioned near the perimeter, arises from protoderm, ground meristem, or procambium, vascular cambium, or cork cambium,
• Types of Sclerenchyma: Fibers and Sclereids
• • Fibers- Type of Sclerenchyma that's long, spindle-shaped. Thick secondary walls. Occur in strands. Support in non-elongating plant parts. With simple or slightly bordered pits that are scarce and slit-like. It has two types:

  1. Soft fibers
  2. Hard fibers
• Sclereids- spicular cells, or stone cells. More isodiametric than fibers. Short, strongly lignified. Thick secondary walls appear multi-layered. With numerous single pits. In epidermis, ground tissue, vascular tissue. Stems, leaves, fruits, seeds. Has 6 types: Brachysclereids, Osteosclereids, Macrosclereids, Astrosclereids, Trichosclereids, Filiform Sclereids
• Brachysclereids- type of sclereids in sclerenchyma that resemble parenchyma cells in shape, but are made almost entirely of secondary cell wall. These non-living cells are also called "stone cells" because they form the "grit" in pear fruits.
• Macrosclereids- type of sclereids in sclerenchyma. One of the columnar sclereids that often form an outer layer in various fruits and seeds, and occur also in the stems of some xerophytes. These are elongated sclereids, responsible for restricting water update by hard-seeded legumes. They are also called "rod cells".
• Osteosclereids- Type of sclereids in sclerenchyma which are also known as "Bone cells". It forms the hypodermal layer in seeds, fruits, and leaves of some plants (in dicots). These are columnar cells that are dilated at the ends.
• Astrosclereids- type of sclereid in sclerenchyma. These are branched, pointed, irregular (often star-shaped) sclereids that can be found in specialized tissues like the floating leaves of water lily.
• Trichosclereids- type of sclereids in sclerenchyma. These are long, slender, and hairlike sclereids.
• Filiform Sclereids- Type of sclereid in sclerenchyma. They are long, fibre-like cells. They are less branched and are not very common, found in the leaves of Olea, etc.
• • Parenchyma- spherical, elongated cells with a thin primary cell wall, no secondary walls.
  • Isodiametric or polyhedral.
  • Abundant intercellular space, and retains the ability to divide.
  • Main component of young plant organs. 
  • Basic functions: photosynthesis and storage. It is also important in regeneration because they are totipotent.
• Classification of Parenchyma cells: Synthetic, Structural, Boundary, Storage, Transport
• 1. Synthetic (Classification of Parenchyma Cells)
  2. Photosynthetic
  3. Meristematic 
  4. Secretory
• 1. Structural (Classification of Parenchyma Cells)
  2. Aerenchyma- soft plant tissues containing air spaces, found especially in many aquatic plants.
• 1. Boundary (Classification of Parenchyma Cells)
  2. Epidermis
  3. Endodermis
• 1. Transport (Classification of Parenchyma Cells)
  2. Transfer cells
  3. Sieve Elements
• 1. Storage (Classification of Parenchyma Cells), stores:
  2. Starches
  3. Proteins
  4. Oils
  5. Water
• • Dermal Tissue- includes the epidermis and the cork layer.
  • Covers the plant and can be found on the outer layer of roots, stems, and leaves. 
  • Main functions: transpiration, gas exchange, and defense. 
• • Root hairs (Dermal Tissue)- to increase surface area
• Trichomes (Dermal Tissue)- used in transpiration or defense.
• Periderm (Dermal Tissue)- found in woody plants. The first line of defense for the plant, protecting it from fire or heat injury, dehydration, freezing conditions, and/or disease. Gives rise to: Cork Cambium and Phelloderm.
• Cork cambium (Dermal Tissue)- produces phellem which is dead tissue that forms the periderm. It also produces phellogen which is living tissue that gives rise to the phelloderm.