Bio notes 4 - Notes Week 4 Biology 103 Spring 2008 Dr Karen...

Week 4
Topic: Plant transport systems
Reading: Chapter 42, sections 4-6
Note: If you have not taken Bi 102, use the links under “Useful Websites” to learn about osmosis, diffusion, and
active transport, processes which are part of plant transport systems.. These concepts are sometimes difficult, but
the animations on the websites help students learn them more quickly and easily.
Main concepts :
• Vascular tissue forms the pipelines of a plant, and is used to transport water, dissolved minerals, and
dissolved sugars.
• Xylem tissue transports water and dissolved minerals from roots to leaves, using some active transport, but
mostly passive processes.
• Phloem tissue transports dissolved sugars up or down a plant, using active transport and osmosis.
• Plants require large amounts of eight nutrients: carbon, hydrogen, oxygen, nitrogen, phosphorous,
potassium, magnesium, and calcium. Other nutrients, such as manganese, copper, sulfur, selenium, and
boron are required in very small amounts.
• Carbon and oxygen are obtained from the air. The rest of the required nutrients are from water and minerals
dissolved in the water.
• Microbes in the soil form symbiotic relationships with root cells which benefit plants by helping them acquire
scarce nutrients.
• Fungal mycorrhizae help plants absorb minerals, especially phosphorous.
• Nitrogen-fixing bacteria convert nitrogen compounds into forms that plants can absorb.
•
Transpiration (water transport) involves three processes: absorption at the roots, capillary action in the
xylem, and evaporation at the leaves.
• Roots acquire dissolved minerals in a four-step process:
• Active transport into the root hairs, which moves minerals against their concentration gradient.