Plant Physiology Notes - Completed.docx

**Plant Physiology Chapter 9** Plants are divided into underground root systems for anchorage and absorption of water and minerals and over ground shoots systems which consist of the stem, leaves, flowers and fruits. A plant cell structure looks like: ![ultrastructure of a plant cell](media/image...

**Plant Physiology Chapter 9** Plants are divided into underground root systems for anchorage and absorption of water and minerals and over ground shoots systems which consist of the stem, leaves, flowers and fruits. A plant cell structure looks like:  **\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_** **Roots** can be: 1. 2. Nutrients are dissolved in the soil solution. Root hairs, with their small size and thin walls, increase the surface area for nutrient absorption from the soil. Nutrients are absorbed from the soil solution through active transport. Active Transport is the movement of a substance from an area of low concentration to a high concentration which needs energy. The energy is got from the mitochondria through a process of respiration. Symbiotic relationships between roots and microorganisms also enhance nutrient uptake. Mycorrhizae, a type of fungus, increase the root surface area, facilitating greater nutrient absorption. Rhizobium, a bacterium, converts atmospheric nitrogen into soluble nitrates usable by the plant. Both microorganisms benefit by receiving sugars from the plant. There are three main categories of plant tissue: 1. 2. 3. Xylem -- Transport water and minerals from the roots up to the leaves. Phloem -- Transports sugars produced by photosynthesis from the leaves to other parts of the plant for storage and use. **Xylem:** All xylem tissue is dead (there is no nucleus or cytoplasm). Lignin reinforces the cell walls. Lignin is strong, water resistant and a durable organic compound. They are found in roots, shoots, leaves and flowers. There are two types: 1. Xylem vessels have no end walls 2. **Phloem:** Composed of sieve tubes and companion cells. Phloem tissue is living. As companion cell are alive, phloem is a living tissue. Sieve tubes are long tubes that form when individual sieve elements join end to end. The end walls are called sieve plates.  Sieve tubes transport food made by photosynthesis to all parts of the plant. Companion cells control the activities of the sieve tube. **Photosynthesis** Plants = Autotrophic -- make their own food. Function of leaves = Photosynthesis (method of producing own food). The leaves are flat. This allows them to absorb as much light as possible to carry out photosynthesis. Chloroplasts contain a pigment called chlorophyll which is located within the thylakoid membrane of the chloroplast. Chlorophyll molecule absorbs light energy from the sun which is the main source of energy on earth.  Photosynthesis is important because: 1. 2. 3. 4. **Respiration** Plant + Animal cells get their energy through aerobic respiration in the form of ATP (Adenosine Triphosphate). *Aerobic Respiration -- the controlled release of energy from glucose in the presence of oxygen.*  Respiration occurs in 2 parts -- Stage 1 = Glycolysis and Stage 2 = Krebs cycle Glycolysis does not require oxygen. Glycolysis occurs in the cytosol. Glucose is broken into two molecules called pyruvic acid.  The pyruvic acid enters into the mitochondria. It is broken down further by releasing a carbon into acetyl coenzyme A. This product enters into the Second stage of aerobic respiration called Krebs Cycle. In the Krebs cycle NADH is produced. Diagram Description automatically generated **Structure of a Leaf:**  **Cuticle:** Is often waxy in nature and prevent water loss from the surface of th leaf. **Upper Epidermis:** Is made of dermal tissue. Its main function is to protect the leaf. **Ground Tissue:** Is made of palisade mesophyll and the spongy mesophyll. The palisade mesophyll contains plant cells which undergo the majority of photosynthesis. The Spongy mesophyll contains cell and vascular tissue. **Lower Epidermis:** Contains the guard cells and the stomata. The guard cells regulate the opening and closing of the stomata. The stomata are the holes/openings on the underside of the leaf which allow oxygen, water and carbon dioxide to diffuse in and out of the plant. **Transpiration** is the loss of water from the surface of the leaves: Leaves control the rate of transpiration by: 1. 2. 3. **Water Transport** Xylem is responsible for the transport of water + minerals from the roots to the leaves. Water is essential for photosynthesis. Water moves from the roots to the leaves by:\ 1. Root pressure 2\. Cohesion -- tension model 3\. Transpiration +-----------------------+-----------------------+-----------------------+ | **1. Root Pressure** | **2. Cohesion -- | **Transpiration** | | | Tension model** | | +=======================+=======================+=======================+ | Caused by the | Water molecules stick | Transpiration is the | | continuous movement | together by a force | loss of water vapour | | of water by osmosis | known as cohesion. | due to evaporation | | from the soil into | | | | the root hairs. | As water is lost by | from the leaves of a | | | transpiration it | plant. | | Osmosis -- the | creates tension, so | | | movement of water | the water is pulled | Transpiration takes | | from an area of high | up the plant. | place through the | | concentration to an | | stomata (openings on | | area of low | Adhesion: When | the | | concentration across | different molecules | | | a semipermeable | stick together. Water | under side of a | | membrane. Osmosis | sticks to the walls | leaf). | | does not require | of the xylem. | | | energy. | | As each water | | | | molecule is pulled | |  | | through the xylem | | | | cells by | | | | | | | | osmosis, the next | | | | water molecule is | | | | pulled also. | | | | | | | | Water is pulled | | | | through the plant by | | | | transpiration | +-----------------------+-----------------------+-----------------------+