B4- [Part 4]- Organising plants 🌱🪴 Flashcards
TRUE OR FALSE: The leaf, is a plant organ?
True- the leaf is a plant organ. [and like any organ, it contains different tissues. ]
What are epidermal cells found ?
Hint: upper, lower
- the top and the bottom of the leaf, are covered with a thin layer of very thin calls- known as epidermal cells.
- epidermal cells, form epidermal tissue.
- the upper epidermis is the top of the leaf; the lower epidermis is at the bottom of the leaf
What is the role of the epidermis ?
Hint: surface
- the role of the epidermis, is to protect the surface of the leaf.
What is the role of the upper epidermis ?
Hint: 💡
- the upper epidermis is transparent, which allows light
- and the upper epidermis, is also covered with a thin layer of oily material. [known as the waxy cuticle]
What is the role of the waxy cuticle ?
Hint: reduce
- the role of the waxy cuticle, is to reduce the evaporation of water from the surface of the leaf.
- This helps to prevent the leaf from drying out
What are the role of stomata ?
Hint: water vapour
- found at the lower epidermis, which has tiny pores:
- stomata allow carbon dioxide to enter the leaf and allow oxygen to diffuse out of the leaf
- ; stomata also help to control the amount of water vapour, that can pass out of the leaf.
What is a second reason why transpiration an important process ? [3]
- the transpiration stream, transports dissolved mineral ions such as magnesium [which play important roles in the plant.]
What is the role of the palisade mesophyll ?
- found at the top of the leaf, the palisade mesophyll consists of palisade cells.
- Palisade cells are packed full of chloroplasts, containing chlorophyll- chlorophyll absorbs the light energy, needed for photosynthesis.
Where are spongy mesophyll located ?
Hint: air spaces
- located underneath the palisade mesophyll, the spongy mesophyll is full of air spaces.
What are spongy mesophyll ? 🧽 [3]
- underneath the palisade mesophyll, the spongy mesophyll is full of air spaces. [think spongy- spongebob- air spaces]
- These air spaces allow carbon dioxide to diffuse from the stomata, through the spongy mesophyll, to the palisade cells.
- [oxygen also diffuses from the palisade cells, through the spongy mesophyll, to the stomata.]
What does xylem tissue does ?
Hint: transports
- xylem tissue transports water from the roots, to the stem and leaves.
- some of the transported water, is them used in photosynthesis.
- the xylem also transports dissolved mineral ions: including magnesium- which is used to make chlorophyll.
What does phloem tissue do ?
Hint: from the leaves
- phloem tissue transports dissolved sugars produced by photosynthesis, from the leaves, to the rest of the plant.
- these dissolved sugars can be immediately used. [e.g- glucose is used in respiration]; the dissolved sugars can also be stored [e.g- starch]
What is translocation ?
Hint: other molcules
- translocation is, the movement of dissolved sugars and other molecules, through phloem tissue.
What is transpiration ?
- transpiration is, the process of water constantly evaporating from the surface of leaves.
What is the difference between translocation 🆚 transpiration ?
- translocation is, the movement of sugars and other molecules, through phloem tissue
- ; transpiration is, the process of water constantly evaporating from the surface of leaves.
What’s a key fact about meristems ?
- meristem tissue contains stem cells, which can differentiate into any type of plant tissue.
- and meristems are found at growing tips [of a plant]: the tips of shoots and the tips of roots
What is the process of the transpiration stream ? [4]
Hint: from cells, through, water passes, up the xyelm
- the process of transpiration begins with: the evaporation of water, from cells inside the leaf.
- water vapour then diffuses through the air spaces in the spongy mesophyll, and out of the leaf through the stomata.
- after that, water passes from the xylem, into the leaf- to replace the water that has been lost.
- and finally, water is drawn into the root hair cells, and up the xylem vessels to the leaf.
What is one reason why transpiration an important process ?
Hint: transports
- transpiration is an important process, because it transports water to the leaf- which is required for photosynthesis. [because it is a reactant of photosynthesis]
What is a third reason why transpiration an important process ?
Hint: weather
- a third reason why transpiration is important is because:
- the evaporation of water from the leaf cools the leaf down, especially in warm weather.
What are the factors that affect the rate of transpiration ?
- the factors which affect the rate of transpiration are:
- 1) light intensity
- 2) temperature
- 3) air flow
- 4) and humidity
How does temperature affect the rate of transpiration?
- temperature affects the rate of transpiration, because the rate of transpiration is greater at higher temperatures.
- This is because, evaporation is faster when temperatures are higher.
How does humidity affect the rate of transpiration ?
- humidity can affect the rate of transpiration, because transpiration is faster under dry conditions [when the air isn’t humid, meaning humidity decreases the rate of transpiration]
- This is because evaporation takes place more quickly, under dry conditions.
Explain how air flow affects the rate of transpiration
- air flow can affect the rate of transpiration, because the rate of transpiration increases in windy conditions.
- this is because wind removes any water vapour, therefore more water to evaporate.
Explain how light intensity increases the rate of transpiration
- light intensity can increase the rate of transpiration, because the rate of transpiration increases, when the light intensity increases.
- This is because, high light intensity increases the rate of photosynthesis.
- Therefore the stomata can open, allowing carbon dioxide to enter
- and once the stomata have opened, water vapour can pass out of the leaf.
What are the role of guard cells ?
- found on either side of the stomata, guard cells surround stomata and:
- the role of guard cells is to allow gas exchange, and control water loss within the leaf.
- this is because, when the light intensity is high [e.g- during the day], the guard cells swell and they change their shape.
- This then causes the stomata to open, allowing carbon dioxide to diffuse into the lead, which can be used in photosynthesis.
What happens to guard cells in hot conditions ?
- in hot conditions, the plant closes its stomata, reducing water loss by transpiration.
- this now means the plant can’t photosynthesise.
Why does the spongy mesophyll have air spaces ?
- the air spaces allow carbon dioxide to diffuse from the stomata, through the spongy mesophyll, to the palisade cells
