Flashcards in CH-08 TRANSPORT IN PLANTS Deck (16)
What do xylem vessels carry?
water and inorganic ions such as nitrate
What substance makes up the cell walls of xylem vessels?
lignin (and cellulose )
What do phloem tubes carry?
sucrose and amino acids
Give three ways in which phloem tubes differ from xylem vessels.
phloem tubes are alive but xylem is dead; phloem tubes have cellulose cell walls, while xylem vessels contain lignin; phloem tubes end in sieve plates, but xylem vessels are open-ended.
What is a vascular bundle?
a collection of xylem vessels and phloem tubes.
What is the function of the root cap?
it protects the tip of the root as it grows through the soil
Explain how water goes into root hairs. How does this process differs from the way in which minerals enter?
water moves into root hairs by osmosis, down its water potential gradient
(or from less concentrated solution to a more concentrated solution one), through the partially permeable cell membrane of the root hair cell. Minerals enter by diffusion or active transport.
What is transpiration?
evaporation of water from the surfaces of mesophyll cells followed by loss of water vapour from plant leaves, through the stomata.
What are stomata?
small holes, mostly on the lower surface of a leaf, surrounded by a pair of guard cells, through which gases can diffuse into and out of the leaf.
What is photometer used for?
measuring the rate at which a shoot takes up water.
Explain how a.temperature,
b. light intensity affects the rate of transpiration.
a. an increase in temperature increases the rate of transpiration. (this happens because, at high temperatures, water molecules have more kinetic energy. They are more likely to turn from liquid to gas, and will diffuse more rapidly out of the leaf)
b. An increase in light intensity increases the rate of transpiration. ( this happens because the plant is more likely to open its stomata when it is light, so allow carbon dioxide to enter for photosynthesis. If stomata are open, more water vapour can diffuse out of the leaf.)
What is the function of the upper epidermis?
Is protects the plant whilst letting the sunshine in as it is thin and transparent
What is the palisade mesophyll?
A layer of palisade cells which absorb light. They are near the surface so light can get to them easily and palisade cells are filled with chloroplasts
What is the spongy mesophyll?
It is filled with air spaces to allow CO2 to diffuse from the stomata tot he photosynthesising cells. It provides a large internal sa:v
What is the lower epidermis?
The lower epidermis is at the bottom of the leaf. It contains guard cells that open and close the stomata where gas exchange happens, water vapour is also lost through the stomata during transpiration