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| Frage | Antworten |
| How is a leaf structured? | |
| What does the waxy cuticle do? | It is a thin waxy layer that is transparent to allow light through to the chloroplasts in the cells of a leaf, it also acts as a barrier to water loss through evaporation and entry of disease by microorganisms - like bacteria |
| How are palisade cells structured? | |
| What is the purpose of palisade cells? | This is the main site of photosynthesis because this the the uppermost layer that contains chloroplasts and is the layer which has the most number of chlroplasts |
| What are the advantages of palisade cells being long and closely packed? | There is more chlorophyll in a small space |
| Where are chloroplasts found? | Found in palisade, spongy and guard cells. |
| What is the mesophyll layer? | It is the middle of the leaf - contains the palisade and spongy layer. |
| Describe the spongy layer. | It is more rounded and less closely packed than the palisade layer. It can photosynthesise but has fewer chloroplasts than the palisade layer. Main site of gas exchange in the leaf. |
| What is the lower epidermis? | It contains the guard cells and stomata |
| Why do leaves have stomata? | To allow the exchange of gases depending on the condition |
| Purpose of guard cells. | Help the stomata to regulate the rate of transpiration by opening or closing. |
| What are the veins in a leaf and why do leaves have them? | They are the xylem and phloem and transport food and water within the plant. |
| Explain the function of xylem. | Water and mineral ions are supplied to the leaf by the xylem, it is part of a continuous transport system. |
| Explain the function of the phloem. | Carries the products of photosynthesis - sugars, from the mesophyll cells to parts of the plant that cannot produce their own food, such as the roots. |
| Which gases are involved in diffusion? | Mainly carbon dioxide and oxygen. |
| How do the cuticle and stomata reduce water loss? | The shiny surface on the cuticle reflects heat and stomata open at night when it is less humid, so less water will evaporate. |
| What are the different parts of a leaf? | |
| What are the purposes for each part of a leaf? | Network of veins - transport system for the plant Petiole - holds the leaf so it can face the sun Lamina (leaf surface) - absorbs light to create nutrients Midrib - supports the leaf and is the main part of the transport system Stem - keeps the leaves in the light |
| How are leaves adapted for efficient photosynthesis? | They are: Broad -to absorb as much light as possible Thin - to speed uo diffusion - \(CO_2\) can easily reach the mesophyll Light - so they are able to grow in a certain angle to recieve as much light possible They have veins to transport water and food Upper epidermis - prevent water loss |
| How does water from the soil reach the leaf? | It is absorbed by the roots and carried upwards by the xylem into the midrib, then into the network of veins |
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