Movement Of Materials Through Plants
Aperçu
A maize plant standing in a dry field is moving water every second of the day. It pulls water from between the soil particles, lifts it metres up a hollow pipework of dead cells, and lets most of it escape as vapour from tiny pores under its leaves. At the same time it is building sugar out of air and sending that food down to its roots and grains. Nothing in the plant has a heart or a pump; the whole traffic is driven by diffusion, osmosis and the simple fact that water evaporates.
In this lesson you will follow materials all the way through a crop plant: in at the root hairs, up the xylem, into the leaf for photosynthesis, and back out through the phloem to the storage organs. You will see why a leaf is built the way it is, how the stomata trade gases, and why hot, dry, windy weather makes a crop wilt. These are the ideas a farmer uses every time they irrigate, space a crop or choose when to transplant.
Objectifs
- (a) describe the distribution and function of root tissues and the structure and function of root hairs.
- (b) explain the absorption of plant requirements from the soil, including the principles of diffusion, osmosis, the passage of water and dissolved mineral salts through vascular tissues.
- (c) explain how the structure of a leaf is related to function (cellular detail is not required).
- (d) outline gas exchange by diffusion through the stomata.
- (e) describe photosynthesis in terms of carbon dioxide, water, light and chlorophyll leading to the synthesis of carbohydrates and the production of oxygen.
- (f) describe the distribution and function of tissues in a stem (dicotyledon only).
- (g) define the term translocation as the movement of synthesised food to storage organs and explain the principles of modification of different parts of plants to form food storage organs and the types of food materials stored.
- (h) explain transpiration in terms of the transpiration stream, loss of water by evaporation and diffusion of water vapour through stomata.
- (i) describe the effects of temperature, humidity, wind and light intensity on the rate of transpiration.
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- Which process takes water into a root from the soil? A. Active uptake B. Osmosis C. Transpiration D. Translocation Answer: B
- In a leaf, gases are exchanged with the air mainly through the: A. Xylem B. Waxy cuticle C. Stomata D. Veins Answer: C
- Which tissue carries food made in the leaves to the storage organs? A. Xylem B. Phloem C. Epidermis D. Cortex Answer: B
- Which set of conditions would give the fastest rate of transpiration? A. Cool, humid and still B. Cool, dry and still C. Hot, humid and still D. Hot, dry and windy Answer: D
- Photosynthesis produces glucose and which gas? A. Carbon dioxide B. Nitrogen C. Oxygen D. Hydrogen Answer: C
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Section de manuel
Transport of Water and Solutes in Plants
Define water potential and explain how it is influenced by solutes, pressure, gravity, and the matric potential
"Biology: Transport of Water and Solutes in Plants" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/biology/pages/30-5-transport-of-water-and-solutes-in-plants. Access for free at https://openstax.org/books/biology/pages/1-introduction
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Section de manuel
Leaves
Identify the parts of a typical leaf
"Biology: Leaves" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/biology/pages/30-4-leaves. Access for free at https://openstax.org/books/biology/pages/1-introduction
Publiées par d'autres organisations sous licence libre, créditées comme elles le demandent. Les liens ouvrent leurs sites.
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