Plant Structure Flashcards
All 27 cards in this deck
What is a root hair cell?
A cell on the outside of a root with a long, thin hair-like extension that absorbs water and mineral ions from the soil.
Which feature of a root hair cell gives it a large surface area?
Its long, thin hair-like extension into the soil, which speeds up absorption of water and mineral ions.
Why does a root hair cell have a thin cell wall and membrane?
It gives a short distance for water and mineral ions to cross, so they are absorbed faster.
By which process does water enter a root hair cell?
Osmosis — from the dilute soil solution into the more concentrated cell.
By which process do mineral ions enter a root hair cell from dilute soil?
Active transport — against the concentration gradient, using energy from respiration.
True or false? Root hair cells contain many chloroplasts.
False. They are underground with no light, so they have no chloroplasts (they have many mitochondria instead).
What does xylem transport, and in which direction?
Water and dissolved mineral ions, upwards from the roots to the stem and leaves only.
What does phloem transport, and in which direction?
Sucrose (dissolved sugars), both up and down the plant to where it is needed.
Which substance strengthens and waterproofs the walls of xylem vessels?
Lignin — it supports the plant and stops the hollow vessel collapsing.
True or false? Xylem is made of living cells.
False. Xylem is made of dead, lignified cells with no end walls, forming hollow tubes; phloem cells are living.
What are sieve plates in phloem?
Perforated end walls between phloem cells that let the sucrose solution flow from cell to cell.
What is the function of companion cells in phloem?
They contain many mitochondria and release energy to actively transport sucrose into the phloem.
Name the tissues of a leaf in order from the upper surface to the lower surface.
Waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll (with vascular bundles), lower epidermis containing stomata and guard cells.
Which leaf cells contain the most chloroplasts, and why are they positioned there?
Palisade mesophyll cells — they are near the top of the leaf to absorb the most light for photosynthesis.
How is the spongy mesophyll adapted for gas exchange?
It has many air spaces, giving a large surface area for carbon dioxide and oxygen to diffuse quickly.
How do stomata open?
The guard cells take in water by osmosis, become turgid and change shape (bulge), opening the pore.
Why is it an advantage to a plant to have stomata on the lower leaf surface and none on the upper surface?
Stomata on the lower surface still allow gas exchange for photosynthesis, while having none on the upper surface reduces water loss by transpiration.
In a drawing of a leaf peel, how do you recognise one stoma?
A pore (gap) surrounded by two sausage-shaped guard cells.
What is a xerophyte?
A plant adapted to survive in very dry (arid) conditions where water is scarce.
How do the small spine-shaped leaves of a cactus help it survive in a desert?
They give a very small surface area, so much less water is lost by transpiration (and they deter herbivores).
How does a thick waxy cuticle help a plant survive in a dry environment?
It is waterproof, so it reduces water loss by evaporation from the leaf surface.
How do rolled leaves and surface hairs reduce water loss in marram grass?
They trap moist air next to the stomata, so less water vapour diffuses out of the leaf.
Why do many xerophytes have stomata sunken in pits?
Moist air is trapped in the pit, reducing the concentration gradient so less water vapour is lost.
True or false? Transport of sucrose in the phloem requires energy from the plant.
True. Phloem is made of living cells, which use energy to move sucrose around the plant.
True or false? The waxy cuticle of a leaf is a layer of living cells that carry out photosynthesis.
False. It is a non-living waxy layer secreted by the upper epidermis; it is transparent and reduces water loss.
Where are the stomata found on the leaves of a floating water plant such as a water lily?
On the upper surface only — this is the surface in contact with the air, so gas exchange can take place there.
How are plants living in cold, windy environments such as the tundra adapted to survive?
They grow low to the ground with small leaves, reducing exposure to wind and water loss.