Lecture 12: Vascular Plants and Vascular Tissue Flashcards
What four major innovations correspond to the four major land plant groups?
- The embryophyte nourishes the developing embryo. This, along with the cuticle layer and stomata made colonzation of land successful. Mosses still need water for fertilization.
- Seedless vascular plants (as well as gymnosperms and angiosperms) have vascular tissue
3.Evolution of the seed, in both gymnosperms and angiosperms
4.Evolution of the flower in angiosperms
What is vascular tissue?
Tissue that transports water, nutrients, and organic compounds like sugars throughout the plant
What is the function of these land plant structures?
Roots
Leaves
Shoots
Roots: are subterranean. They anchor the plant and absorb water and minerals
Leaves: are aerial portions of the plant, and the cite of most photosynthesis
Shoots: functions to support the plant and are also important in transport
What are the two functions of vascular tissue?
- Moves water nutrients and food up and down the plant
- Supports the plant so they can grow larger
What is a xylem and what are the two types of xylem cells?
Xylem conducts water and minerals from the roots to the leaves (upward).
The 2 types of xylem cells are tracheids and vessels.
What are tracheids?
Tracheids are xylem cells that are thin with tapered ends. Water travels up these cells like a straw from the roots to the leaves.
What are vessels in the xylem?
Vessels are wider and more open than tracheids. They transport water more efficiently, and is a reason why angiosperms are so successful.
What is lignin? and what does it mean when we say that xylem is dead tissue?
Lignin is a hard material that provides support for the plant. It forms long hollow tubes that act as support for the plant.
Xylem is dead tissue because the cells are empty. The water and nutrients are free to move without the hindrance of cellular cytoplasm.
How does xylem sap move up the xylem and what are its features? (7)
Xylem sap moves up the xylem by transpiration-cohesion.
1. Transpiration is evaporation of water from leaves into the air through stomata. This moves water towards the leaves to a less concentrated area.
2. Water is cohesive, so it stays together
3. Net effect is like a straw. Water is sucked out the top and shoot is analogous to a straw.
4. Process requires no energy from the plant
5. Enormous of water can be transported up shoots into leaves
6. More than 90% of water is transported up the xylem sap and is lost to evaporation so it is very inefficient
7. Water column itself acts as a support mechanism for the plant.
What is phloem?
Phloem is the vascular tissue that conducts organic compounds from the leaves to the roots and to other structures that need a lot of sugar.
What are sieve elements?
Sieve elements conduct nutrients and are alive.
- They lack nuclei
- Their cell walls have pores in their end walls, so sugars can go between them (sieve plates)
- When the sieve elements are laid end-to-end organic compounds make their way along the sieve tube
- Sieve element cells are fragile and therefore short-lived
What are companion cells?
Companion cells help regulate the movement of sugars through the sieve tube and help keep sieve tube cells alive.
What gets transported in the phloem?
Sugars, amino acids, hormones, even viruses
What is the process by which compounds get moved in the phloem?
First, energy is used to load organic compounds into the sieve tube members. This stimulates the movement of water towards the phloem sap, forcing the organic compounds down the tube. At the end of the tube, the compounds are “unloaded” to be used by needy cells.
What are the three uses of water that is taken up by roots and transferred by transpiration?
- Most of it is lost to evaporation. Column of water does, however, provide support.
- Some water is used for photosynthesis and other cellular processes
- Some of the water enters the sieve elements and contributes to the phloem sap. Can be returned to the leaves via the xylem.
