Topic 9 Plants Unit Flashcards
Review for Biology Exam
Describe xylem’s structure and how it allows water transport. [2 marks]
- Dead, hollow cells stacked ends to ends allows water movement.
- Lignin-impregnated walls allows it to withstand low pressure for water transport.
Describe how water’s properties relates to its transport in xylem. [ 2 marks]
- Its adhesion to the mesophyl cell walls, allows tension force to exert on the water column in the xylem when water evaporates.
- Its cohesion allows the tension force to be transmitted from shoot to root without caviation.
Describe water’s movement in leaves during gas exchange. [2 marks]
- Water evaporates when stomata opens for gas exchanges, causing transpiration.
- New water molecules replaced the evaporated one from the xylem water column due to water adhesion to mesophyl cell wall.
Describe the process whereby water enter the roots and xylem. [4 marks]
- Active transport of ions into root cells causes water to enter the roots via osmosis.
- Water might reach the Caspian strip through plasmodaeta symplastically or between cell walls apoplastically.
- All pathways of water is absorbed into the Caspian strip before being moved into the xylem.
- This is called mass flow.
Define halophytes and state how they conserves water. [3 marks]
- Halophytes are plants living in saline conditions.
- They have specialized tissues to remove salt.
- They uses stems to photosynthesize.
Define xerophytes and describe how they converved water. [5 marks]
- Xerophytes are plants living in dry habitats.
- Ephemeral ones conserves water by being active only in rainy seasons.
- Perrenials ones hoards water in specialized tissues.
- Some other plants restrict transpiration by shielding stomata with needled-sized or closed, sunken leaves.
- Some plants transform carbon dioxide into malic acid at night to limits gas exchange during the day. This is called the Crusselean acid metobolism, and occurs in C4 physiology.
What effect does increased soil salinity have on water transport in the plant roots?
A. Decreases movement of water from soil into the root
B. Absorption of water with a higher solute concentration
C. Increases movement of water from soil into the root
D. Absorption of water with a lower solute concentration
A
Which process and cause are responsible for water uptake by the roots?
A. Simple Diffusion
B. Osmosis since [roots solute] is greater than [soil]
C. Osmosis since [roots solute] is less than [soil]
D. Cohesion
B
Outline active transport in phloem tissue. [2 marks]
- Proteins pumps employs ATP to move protons out. When the protons diffuse back in through protons channels, sucrose is co-transport into the companion cell from apoplastic pathway.
- Proteins pumps then moved the sucrose into the sieve tube cell actively.
- Loading and unloading at sources and sinks.
Explain how a plant replaces the water it loses in transpiration. [3 marks]
[Any 3 of 5]
1. Water evaporating due to transpiration causes another one to take its place from the xylem.
2. Its adhesion property causing tension the xylem water column causing water to be drawn out.
3. The tension is transmitted down to the roots with water’s cohesion.
4. To avoid caviation root pressure causes water to enter the cell.
5. These waters entered the roots via osmosis when ions are actively transport into the roots.
Explain gas exchange in plants and its contribution to repsiration. [2 marks]
- Gas exchange is neccesary to supply photosyntheis with CO2 and replace O2.
- It also allows substance to exit the leaves through stomata.
Outline roots absorption of water. [3 marks]
- A 100x higher solute concentration is established in roots by protein pumps.
- Water osmosis into the cells, either apoplastically or symblasticly through the plasmodeta.
- Water is absorbed by the Caspian strip then moved to the xylem.
Outline how plants absorbed ions attached to soil’s surface using fungi. [2 marks]
[Any 2 out of 3]
1. Some plants allows fungi to grow over or into the roots cells.
2. The fungi collects ions like phosphate, in exchange for sugars and nurtrients.
3. Plants are able to grow in minerally deficit soils.
Which plants store water in specialized tissues to conserve water in dry climates?
Perrenial Xerophytes
Which plants only become active in short rainy seasons to conserve water in dry habitats?
Ephemeral Xerophytes
Which plants process allows plants to conserve water by being active at night to limit respiration during the day? [2 marks]
What substance is involved? [1 mark]
- Crusselean Acid Metabolism
- C4 physiology
- Malic Acid
States all adaptions that conserve waters employed by xerophytes. [4 marks]
- Being active only during rainy seasons.
- Store water only in specialised tissues.
- Convert CO2 into malic acid at night so that no respiration and thus transpiration occured during the day.
- Curled up leaves with stomata at the curl bottom reduce opening OR hair around stomata stop air movement and prevent respiration.
States halophytic adaptions to conserve water in salty conditions. [4 marks]
- Scaly leaves and stem
- Internal water storage
- Thickened cuticles & epidermis
- Salt removing structure.
Draw a xylem structure.
Check textbook.
States components of a phloem sieve tubes cells. [3 marks]
- Sieve tube
- Peforated sieve tube plates between each sieve tubes.
- Companion Cell
State functions of phloem. [2 marks]
What it transports, and from where to where?
- Phloem transport sugars and amino acids, called translocation.
- Phloem transport them from source to sink.
Differientiate source and sink. [2 marks]
- Sources is where there is a suplus of amino acids and sugars. Sink is where there is a deficite.
- Souces is where substance is loaded, sink is where it is unloaded.
Explain how phloem maintain flow in any direction. [1 marks]
- Phloem actively expend energy to maintain a pressure gradient that allows translocation to occured.
Define translocation. [1 marks]
- It is the transport of organic solutes from sources to sink.
