Lecture 12 Vascular Plants and Vascular Tissue Flashcards
Roots
Leaves
Shoots
Roots: are subterranean (under the terrain). They anchor the plant and absorb water and minerals
Leaves: aerial portions (in the air) of the plant and the sight of most photosynthesis
Shoots: function to support the plant and important in transport
What type of transport is the xylem responsible for?
Water, essential nutrients, and minerals like nitrogen need to be transported from the soil to other parts of the plant
Besides transport, what is another important function of xylem?
Support as land plants could not grow more than a few centimeters without it
Phloem
A type of vascular tissue that conduct organic compounds downwards from the leaves into the roots and other structures that need sugar (fruits ie)
Xylem
Definition, types
Conducts water and minerals from the roots to the leaves
1. Tracheids: thin with tapered ends. Have holes on ends and sides and cells are laid end to end so that cells can form a long tube so water can travel up from the roots to the leaves
2. Vessels: wider and their ends are more open. Transport water more efficiently
What is evidence that vessels have originated more than once
They are found in angiosperms (which are more successful than other plants) which is evidence that vasculae tissue has evolved over time
What are two important features of xylem?
NOT functions!
- Contains lingin- hard material that provided support for the plant
- It is dead tissue so the cells are empty soo water and nutrients (aka xylem sap) are free to move without hindrance of cellular cytoplasm
What are the 7 features of transpiration-cohesion of the xylem
- Transpiration is the evaporation from leaves into the air through the stomata (Water moves towards cells when it is lost from leaves and begins a chain reaction)
- Water is cohesive meaning it tries to stay together
- The net effect is like a straw where water is sucked out of the top of the straw
- Requires no energy
- An enormous amount of water can be translated up shoots into leaves
- More than 90% of the water transported up xylem sap is lost to evaportation (INEFFICIENT!)
- Water column acts as a support mechanism in addition to lingin
Sieve elements
- Cells that conduct nutrients
- They are alive but lack a nucleus.
- Cell walls have pores in their end walls so sugars can go between cells called “sieve plates”
- Fragile and short lives
- associated with (next to) companion cells which loads nutrients and tranfers them into sieve elements
What gets transpported in the phloem
Sugar, amino acids, hormones, even viruses
What is the process by which compounds get moved
Organic compounds are looaded into the sieve tube members which requires the expenditure of energy. Once they are loaded, the organic compounds are at very high concentration in the phloem sap. Because water moves from high to low concentrations, organic concentrations move from low to high and the pressure forces the organic compounds down the tube and unloaded from sieve tubes to be used by needy cells.
The water is taken up by roots and is transferred by transpiration to leaves has three uses:
- Most of it is lost to evaporation (column of water in the shoots provide support for plants, however)
- Some of it used for photosynthesis and other processes (photosynthesis requires water)
- Some of it enters the sieve elements and contributes to the phloem sap (water goes to any “sink”)
Life cycle of seedless vascular plants/ ferns
- Like all plants they are embryophytes
- Sporophyte is dominant and represents a major evolutionary trend. (Speculation that evolution on land facors having two copies of genes due to harmful effects of UV radiation)
- Although the sporophyte is dominant, there is still a seperate gametophyte
- Sperm still needs water so sexual reproduction is still dependent on water (need to reproduce in wet environments)
