Biology
- Phloem & Xylem
Are Phloem and Xylem Similar? What are the Differences? Similarities: Phloem and xylem are tissues in a plant that transport food and water. Both are vascular tissues and when they work together to effectively transport food, water and minerals they form...
- #42 Summary Of Transport In Multicellular Plants
1. Multicellular organisms with small surface area to volume ratios need transport systems. 2. Water and mineral salts are transported through a plant in xylem vessels. Movement of water is a passive process in which the water moves down a water...
- #41 Transport In Phloem
The movement of substances in phloem tissue is called translocation. The main substances that are moved are sucrose and amino acids, which are in solution in water. These substances have been made by the plant and are called assimilates. Phloem...
- #40 Movement Of Water And Minerals In The Xylem
Most plants secure the water and minerals they need from their roots. The path taken is: soil -> roots -> stems -> leaves. The minerals (e.g., K+, Ca2+) travel dissolved in the water. Water and minerals enter the root by separate paths which...
- #39 Structure Of Transport Tissues In Plants
Plants have 2 transport systems: xylem: transports water and inorganic ions from the roots to the leaves.phloem: transports food made in the plant (sucrose and amino acids) from the leaves to the rest of the plant. Both of...
Biology
#38.2 Transport in multicellular plants - Syllabus 2016
7.1 Structure of transport tissues
7.2 Transport mechanisms
Flowering plants do not have compact bodies like those of animals. Leaves and extensive root systems spread out to obtain the light energy, water, mineral ions and carbon dioxide that plants gain from their environment to make organic molecules, such as sugars and amino acids. Transport systems in plants move substances from where they are absorbed or produced to where they are stored or used. Plants do not have systems for transporting oxygen and carbon dioxide; instead these gases diffuse through air spaces within stems, roots and leaves.
7.1 Structure of transport tissues
Plants have two transport tissues: xylem and phloem.
a) draw and label from prepared slides plan diagrams of transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants using an eyepiece graticule to show tissues in correct proportions (see 1.1c)
b) draw and label from prepared slides the cells in the different tissues in roots, stems and leaves of herbaceous dicotyledonous plants using transverse and longitudinal sections
c) draw and label from prepared slides the structure of xylem vessel elements, phloem sieve tube elements and companion cells and be able to recognise these using the light microscope
d) relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions
7.2 Transport mechanisms
Movement of xylem sap and phloem sap is by mass flow. Movement in the xylem is passive as it is driven by evaporation from the leaves; plants use energy to move substances in the phloem.
Xylem sap moves in one direction from the roots to the rest of the plant. The phloem sap in a phloem sieve tube moves in one direction from the location where it is made to the location where it is used or stored. At any one time phloem sap can be moving in different directions in different sieve tubes.
a) explain the movement of water between plant cells, and between them and their environment, in terms of water potential (see 4.2. No calculations involving water potential will be set)
b) explain how hydrogen bonding of water molecules is involved with movement in the xylem by cohesion-tension in transpiration pull and adhesion to cellulose cell walls
c) describe the pathways and explain the mechanisms by which water and mineral ions are transported from soil to xylem and from roots to leaves (include reference to the symplastic pathway and apoplastic pathway and Casparian strip)
d) define the term transpiration and explain that it is an inevitable consequence of gas exchange in plants
e) investigate experimentally and explain the factors that affect transpiration rate using simple potometers, leaf impressions, epidermal peels, and grids for determining surface area
f) make annotated drawings, using prepared slides of cross-sections, to show how leaves of xerophytic plants are adapted to reduce water loss by transpiration
g) state that assimilates, such as sucrose and amino acids, move between sources (e.g. leaves and storage organs) and sinks (e.g. buds, flowers, fruits, roots and storage organs) in phloem sieve tubes
h) explain how sucrose is loaded into phloem sieve tubes by companion cells using proton pumping and the co-transporter mechanism in their cell surface membranes
i) explain mass flow in phloem sap down a hydrostatic pressure gradient from source to sink
7.2 Transport mechanisms
Flowering plants do not have compact bodies like those of animals. Leaves and extensive root systems spread out to obtain the light energy, water, mineral ions and carbon dioxide that plants gain from their environment to make organic molecules, such as sugars and amino acids. Transport systems in plants move substances from where they are absorbed or produced to where they are stored or used. Plants do not have systems for transporting oxygen and carbon dioxide; instead these gases diffuse through air spaces within stems, roots and leaves.
Learning Outcomes
Candidates should be able to:
Candidates should be able to:
7.1 Structure of transport tissues
Plants have two transport tissues: xylem and phloem.
a) draw and label from prepared slides plan diagrams of transverse sections of stems, roots and leaves of herbaceous dicotyledonous plants using an eyepiece graticule to show tissues in correct proportions (see 1.1c)
b) draw and label from prepared slides the cells in the different tissues in roots, stems and leaves of herbaceous dicotyledonous plants using transverse and longitudinal sections
c) draw and label from prepared slides the structure of xylem vessel elements, phloem sieve tube elements and companion cells and be able to recognise these using the light microscope
d) relate the structure of xylem vessel elements, phloem sieve tube elements and companion cells to their functions
7.2 Transport mechanisms
Movement of xylem sap and phloem sap is by mass flow. Movement in the xylem is passive as it is driven by evaporation from the leaves; plants use energy to move substances in the phloem.
Xylem sap moves in one direction from the roots to the rest of the plant. The phloem sap in a phloem sieve tube moves in one direction from the location where it is made to the location where it is used or stored. At any one time phloem sap can be moving in different directions in different sieve tubes.
a) explain the movement of water between plant cells, and between them and their environment, in terms of water potential (see 4.2. No calculations involving water potential will be set)
b) explain how hydrogen bonding of water molecules is involved with movement in the xylem by cohesion-tension in transpiration pull and adhesion to cellulose cell walls
c) describe the pathways and explain the mechanisms by which water and mineral ions are transported from soil to xylem and from roots to leaves (include reference to the symplastic pathway and apoplastic pathway and Casparian strip)
d) define the term transpiration and explain that it is an inevitable consequence of gas exchange in plants
e) investigate experimentally and explain the factors that affect transpiration rate using simple potometers, leaf impressions, epidermal peels, and grids for determining surface area
f) make annotated drawings, using prepared slides of cross-sections, to show how leaves of xerophytic plants are adapted to reduce water loss by transpiration
g) state that assimilates, such as sucrose and amino acids, move between sources (e.g. leaves and storage organs) and sinks (e.g. buds, flowers, fruits, roots and storage organs) in phloem sieve tubes
h) explain how sucrose is loaded into phloem sieve tubes by companion cells using proton pumping and the co-transporter mechanism in their cell surface membranes
i) explain mass flow in phloem sap down a hydrostatic pressure gradient from source to sink
- Phloem & Xylem
Are Phloem and Xylem Similar? What are the Differences? Similarities: Phloem and xylem are tissues in a plant that transport food and water. Both are vascular tissues and when they work together to effectively transport food, water and minerals they form...
- #42 Summary Of Transport In Multicellular Plants
1. Multicellular organisms with small surface area to volume ratios need transport systems. 2. Water and mineral salts are transported through a plant in xylem vessels. Movement of water is a passive process in which the water moves down a water...
- #41 Transport In Phloem
The movement of substances in phloem tissue is called translocation. The main substances that are moved are sucrose and amino acids, which are in solution in water. These substances have been made by the plant and are called assimilates. Phloem...
- #40 Movement Of Water And Minerals In The Xylem
Most plants secure the water and minerals they need from their roots. The path taken is: soil -> roots -> stems -> leaves. The minerals (e.g., K+, Ca2+) travel dissolved in the water. Water and minerals enter the root by separate paths which...
- #39 Structure Of Transport Tissues In Plants
Plants have 2 transport systems: xylem: transports water and inorganic ions from the roots to the leaves.phloem: transports food made in the plant (sucrose and amino acids) from the leaves to the rest of the plant. Both of...