Plant Structure and Function A Meridian Biology AP Study Guide by John Ho and Tim Qi Plant Terms Growth: Growth Types Type Location Description Primary Primary Vertical growth (up-down), dominant direction in most plants. Meristem Secondary Lateral Meristem Horizontal growth (left-right), adds layers to the plant thickening stems and roots. Meristem: Unspecialized embryonic plant tissue found in areas of growth Apical Meristem: Type of primary meristem located at the tip of stems or roots where cell division occurs. Vascular Cambium: Lateral meristem found in stems that develops into secondary xylem (inwards) and secondary phloem (outwards). Plant Growth Primary Growth Secondary Growth Primary Meristem Apical Meristem Lateral Meristem Vascular Cambium Ground Tissue Secondary Xylem (wood) Procambium Vascular Tissue Secondary Phloem (bark) Periderm Cork Cambium Copyright 2006 (March 2 nd ) All rights reserved. Study Guide v1.6 by Meridian notes. Do not distribute or reproduce without replicating this copyright
Plant Tissue: Primary Growth Types Type Region Description Dermal Outer Outer region made up of dead cells that act as a protective covering aginst the environment and water loss. Ground Contains parenchyma, collenchyma, and sclerenchyma. Performs photosynthesis and adds to structural support. Parenchyma Thin-walled cells found in mostly in younger sections of (Youngest) plants. Most of photosynthesis occurs in these cells Collenchyma Mid Supporting cells with thicker walls that make up much of the (Mid-aged) stem. Sclerenchyma (Oldest) Rigid dead support cells with a secondary cell wall. The pith and bark are made up of these cells Vascular Inner Center tissue responsible for transporting water and other minerals. Transportation Structures Water Potential: Determines direction of osmosis (high to low) Water Potential (Ψ) Value (Ψ) Solute Level Description (-) Negative Higher Water is absorbed from surrounding environment (0) Zero Same Potential of pure water, no amount is lost or gained (+) Positive Lower Water is lost to surrounding environment Transpiration Pull: Accounts for water movement up the xylem. Water lost from evaporation causes extremely low (negative) water potential towards the top of the plant. Water diffuses upwards, providing the necessary reactant for photosynthesis without expending energy. Translocation: (Pressure Flow Hypothesis) Movement of sugar from sources to sinks during the build-up of pressure when a high concentration of sugar draws in water. 2. Active transport into phloem 3. Osmosis of water into the phloem 1. Build-up of sugar 4. Build-up of pressure 5. Movement towards lower pressure
Sources and Sinks Type Plant Part Description Spring Winter Source Leaves Root Leaves undergo photosynthesis, producing sugar which is stored in the roots. Sink Root Leaves Roots send stored sugar into the upper portions of the plant, which now act as the sink. Xylem and Phloem: Xylem and Phloem Type Transports Description Xylem Hollow, dead cells that act as a funnel through which water is transported via transpiration pull. Tracheids Water Found in gymnosperms, long thin tubes for water transport. Vessel Elements Found in angiosperms, thicker tubes than tracheids and more efficient at transporting material. Phloem Living tissue that carries organic nutrients Sieve tube elements Sugar Forms a tube of cells joined end to end, lack many organelles and rely upon companion cells for survival. Companion cells Linked to sieve tube element (through plasmodesmata), metabolically active and provided sieve tube cells with nutrients. Tracheophytes: All vascular plants with specialized tissue for transporting water (xylem and phloem). Includes ferns, gymnosperms and angiosperms. Vascular Tissue Xylem: Water Phloem: Sugar Tracheids Vessel Elements Sieve Tube Elements Companion Cells Plant Miscellaneous Components Plant Cell Organelles Tonoplasts Large membrane bound compartments that maintain turgor pressure (stiffness). Leucoplasts Plant organelle for bulk storage (such as sugar), found in roots. Ligin A polymer that binds cellulose together to form cell walls. Suberin Waxy, water-resistant substance found in the Casparian Strip and the cork.
Root Structure and Types Root Systems: Root Types Taproot One main, vertical root from which thinner, horizontal roots (lateral roots) grow from. Fibrous Root Dense mat of thin roots that are typically shallow. Adventitious Root System where the stem lays horizontal, allowing roots to grow from the stem downwards. Root Function: 1) Anchor plant, 2) Absorb nutrients, and 3)Store nutrients Root Growth : Root (ground level to root cap) Zone of Maturation Zone of Elongation Zone of Cell Division Root Transportation: Apoplastic route Symplastic route Transportation Routes Pathway in between cells (through gaps in between cell walls) water molecules diffuse through to reach the vascular cylinder Pathway within cells (through the cytoplasm) water molecules diffuse through to reach the vascular cylinder Root Structure: Stele: Also vascular cylinder, it is the innermost vascular tissue, located in the center in roots and around the pith (if present) in the stem. Casparian Strip: Waterproof strip between the cortex and stele (within endodermis) which controls water entry in the vascular tissue.
Leaf Structure and Functions Leaf Structure: Cross-Section: Blade: A fully mature plant leaf, including all parts up to the stem. Petiole: Stalk attaching the blade to the plant s stem. Stoma and Guard Cells: Located in the underside of the leaf, responsible for gas exchange. Regulation of Stoma Type Turgor K+ Ion Description Pressure Amount Closed Low Low Loss of K+ ions from the guard cells causes water to flow out, relaxing the pressure and causing the stoma to close. Open High High Influx of K+ ions into the guard cells causes water to flow in, raising the pressure and opening the stoma.