How does the structure of epidermal tissue aid its function?
Epidermal tissues cover the surfaces and protect the leaf. These cells often secrete a waxy substance that waterproofs the surface of the leaf.
How does the structure of palisade mesophyll aid its function?
Palisade mesophyll tissue contains lots of chloroplasts, which carry out photosynthesis.
How does the structure of spongy mesophyll aid its function?
Spongy mesophyll tissue contains some chloroplasts for photosynthesis but also has big air spaces and a large surface area to make the diffusion of gases easier.
How do the structures of xylem and phloem aid their function?
Xylem and phloem are the transport tissues in plants. Xylem carry water and dissolved mineral ions from the roots up to the leaves and phloem carry dissolved food from the leaves around the plant.
What is the meristem tissue?
The meristem tissue at the growing tips of roots and shoots is made up of rapidly dividing plant cells that grow and differentiate into all the other cell types needed.
What is the stomata
All over the leaf surface are small openings known as stomata. The stomata can be opened when the plant needs to allow air into the leaves. Carbon dioxide from the atmosphere diffuses into the air spaces and then into the cells down a concentration gradient. At the same time, oxygen produced by photosynthesis is removed from the leaf by diffusion into the surrounding air. This maintains a concentration gradient for oxygen to diffuse from the cells into the air spaces of the leaf.
What are the guard cells and what is their function
The size of the stomata and their opening and closing is controlled by the guard cells.
Define transpiration
transpiration the loss of water vapour from the leaves of plants through the stomata when they are opened to allow gas exchange for photosynthesis. It involves evaporation from the surface of the cells and diffusion through the stomata
How do you investigate the distribution of the stomata and the guard cells?
You apply a thin coat of nail varnish onto the surface of the leaf you want to conduct your investigation on. Then , when it dries, you peel it off with forceps and put upon a microscope slide to investigate.
How can you measure rate of transpiration?
An apparatus known as a potometer can help do so. A potometer can be used to show the uptake of water in different conditions. This helps you estimate how much water the plant has lost in transpiration as that is where most of it going, however a smalk amount is also used in the metabolism, such as photosynthesis
What is the effect of changing temperature on the rate of transpiration?
Temperature affects the rate of transpiration in several ways. The molecules move faster as the temperature increases, so diffusion occurs more rapidly. The rate of photosynthesis also increases as the temperature goes up, so more stomata will be open for gas exchange to take place, meaning that higher temperatures means more increased rate of transpiration
What is the effect of light intensity of changing on the rate of transpiration
When stomata are open, the rate at which water is lost by evaporation and diffusion increases. Therefore, an increase in light intensity will increase the rate of transpiration.
What is the effect of air movement on the rate of transpiration
Hot, dry, windy conditions increase the rate of transpiration because more water evaporates from the cells and diffusion happens quicker. Water vapour diffuses more rapidly into dry air than into humid air because the concentration gradient is steeper. Windy conditions both increase the rate of evaporation and also maintain a steep concentration gradient from the inside of the leaf to the outside by removing water vapour as it diffuses out.
What is the effect of humidity on the rate of transpiration
Water vapour diffuses more rapidly into dry air than into humid air because the concentration gradient is steeper, hence an increase in humidity will decrease the rate of transpiration
What organs make up the plant transport system
Plants have two different transport systems. One is for food, which is glucose and is transported via the phloem. The other is for water and mineral ions, which are transported via the xylem
3 Root hair cells adaptations
• They greatly increase the surface area available for water to move into the cell.
• They have a large permanent vacuole that speeds up the movement of water by osmosis from the soil across the root hair cell.
• They have many mitochondria that transfer the energy needed for the active transport of mineral ions into the root hair cells.
3 Xylem cell adaptations
- Alive when first formed, but soon die and are hollow tubes with lignin spirals that allow water and mineral ions to move with ease
- The spirals and rings of lignin in the plant make them very strong and capable of withstanding the pressure of the moving water within it
- support plant stem
3 Phloem adaptations
- form tubes of phloem cells, but the cell walls in between break down to form special sieve plates that allow water carrying dissolved food to move freely throughout the plant
- domt have a lot of their organelles, such as their nucleus to maximise space for nutrient transportation
- supported by companion cells that keep them alive. The mitochondria in these cells provide the phloem with energy to move the food up and down the plant
Define translocation
The movement of sugars from the leaves to the rest of the plant through the phloem
What is the word equation of photosynthesis
Carbon dioxide + Water — ( with chlorophyll and light) ——> Glucose + Oxygen
What is the symbol equation for photosynthesis
6CO2 + 6H2O ——— ( with light and chlorophyll)—-> C6H12O6 + 6O2
Why is photosynthesis an endothermic reaction
It is an endothermic reaction because it requires an input of energy from the environment, which is the sunlight
Give 6 leaf adaptations
1) contain chlorophyll in chloroplasts - absorb light for photosynthesis
2) very thin - convinient for diffusion of gases
3) broad - increased surface area for maximum absorption of sunlight
4) have veins - help bring water, remove photosynthesis products
5) they have air spaces that allow carbon dioxide to get to the cell/ oxygen to leave
6) have guard cells - open/ close stomata to regulate gas exchange
How is light intensity a limiting factor for photosynthesis
Light is needed for photosynthesis to occur as it’s an endothermic reaction. For most plants, the brighter the light, the higher the rate of photosynthesis if all other conditions are met
