Topic 7 Transport In Plants. Flashcards
What is a dicotyledon?
A dicotyledon, or dicot, is a flowering plant with two cotyledons that emerge during seed germination.
Key features of dicots include:
- Dicot leaves have a broad, flattened shape with a network of veins.
- The floral organs usually occur in multiples of 4 or 5.
- They have a taproot system, with a main central root that grows deeper into the soil.
What are the two functions of transport in plants?
- Transporting water, mineral ions and nutrients such as sugars produced during photosynthesis.
- Facilitating the uptake of carbon dioxide and the release of oxygen.
What is ground tissue?
Ground tissue is a plant tissue that functions in photosynthesis, storage, and support. It is is categorized into three main types:
- Parenchyma: A type of ground tissue with thin-walled cells that are involved in storage, photosynthesis, and tissue repair e.g. cortical cells, pith cells and mesophyll cells.
- Collenchyma: Provides flexible support, particularly in young stems and leaves, with thicker cell walls e.g. outer cortical cells.
- Sclerenchyma: Consists of rigid cells that offer structural support, often having thick, lignified walls and usually being dead at maturity e.g. tree branches and cortical cells of harder stems.
What is vascular tissue?
What are the two vessels/tissues of the vascular system?
Vascular tissue is a tissue in plants consisting of mainly xylem and phloem but also containing scelerenchyma and parenchyma cells.
The two main types of vessels in the vascular system of plants are:
- Xylem vessels.
- Phloem vessels.
What is xylem?
Xylem is a non-living lignified plant vascular tissue containing tubes called vessels that transports water and dissolved mineral salts (inorganic compounds) from the roots to the rest of the plant in a transport process called transpiration while providing physical support to the plant.
Xylem tissue consists of several types of cells, primarily:
- Fibres.
- Vessel elements.
- Parenchyma cells.
What are the five adaptations of the xylem?
- Cells are joined end to end with no cross walls to form a long continuous tube to allow free passage of water.
- Cells are dead, without cell contents, to allow free passage of water.
- Outer walls are thickened with a substance called lignin, strengthening the tubes, which help support the plant and allows adhesion of water.
- Pits in the walls formed from plasmodesmata allow water in and out of the tubes.
- Large lumen which allows for the transport of large volumes of water at once.
What is phloem?
Phloem is the living tissue in vascular plants containing tubes called sieve tubes that transports the soluble organic compounds called assimilates (e.g. sucrose and amino acids) made during photosynthesis from the source to the sink. This transport process is called translocation.
Phloem tissue consists of several types of cells, primarily:
- Sieve tube elements: They are arranged end-to-end to form long sieve tubes and lack a nucleus at maturity.
- Companion cells: Support sieve tube elements by facilitating the loading and unloading of sugars and nutrients, while also aiding in communication and metabolic processes.
Sources as the parts of plants that release sucrose or amino acids.
Sinks as the part of plants that use or store sucrose or amino acids.
What are the adaptations of phloem vessels?
- The cells are joined end to end to form long sieve tubes and contain holes in the end cell walls (called sieve plates) which allow easy flow of substances from one cell to the next.
- Phloem tubes are made of living cells that transport sap containing sugars produced during photosynthesis to non-photosynthetic parts of the plant or storage structures.
Structure and how its related to its function:
- Sieve tube elements have many plasmodesmata to allow efficient communication and nutrient transfer with companion cells.
- Sieve tubes in the phloem have cellulose in their cell walls, which provides some structural support.
- Sieve tube elements have few organelles which allow for more efficient transport of nutrients, as there is more space for the flow of sap. They have a cellulose cell wall, plasma membrane, few mitochondria and endoplamic reticulum, however, they have no nucleus, ribosomes, vacuole or tonoplast.
What are the adaptations and functions of companion cells?
- Companion cells have numerous organelles such as many mitochondria for ATP production via aerobic respiration for use in active transport during translocation and many ribosomes and rough endoplasmic reticulum for polypeptide production. They also have a nucleus, vacuole, tonoplast and mitochondrion.
- Companion cells have numerous plasmodesmata connections across cell walls which allow for direct communication and transfer of substances between companion cells and sieve tube elements.
What is the direction of movement in the xylem and phloem?
Movement in the xylem only takes place in one upwards direction (from roots to leaves) unlike phloem where movement takes place in different directions.
What is the pathway of water from the soil to the atmosphere?
Soil → Root hair cell → Root cortex cells → Endodermis → Xylem → Leaf mesophyll cells → Stomata → Atmosphere.
Describe the structure of root caps and root hairs?
Structure of Root Caps:
- Found at the tip of the root, and is tough providing protection against mechanical damage as the root grows.
- It is impermeable to water, preventing excessive absorption.
Structure of Root Hairs:
- Thin, single-celled, hair-like extensions of root epidermal cells.
- Composed of a permeable cell wall that facilitates water and nutrient uptake.
- The large surface area of root hairs increases the uptake of water and mineral ions.
Describe the pathway of water from the soil to the root hair cells.
Water enters the root hairs by osmosis where water moves from the surrounding soil (higher water potential) into the root hairs (lower water potential because of the high concentration of ions and organic substances) through a partially permeable cell surface membrane down the water potential gradient into the vacuole and cytoplasm of root hair cells.
ψ is the symbol for water potential.
