4. Bioenergetics Flashcards
What is the epithelial tissue?
Tissue that covers the whole of the plant
What is the mesophyll tissue?
Tissue where photosynthesis is carried out
What is the vascular tissue?
Tissue where the xylem and phloem transport substances around the plant
What is the meristem tissue?
The tissue found at the growing tip of plants
What are some adaptations of plants and the purpose?
They have chlorophyll- to absorb sunlight
They have a large surface area- to let them absorb more light
They have stomata- to let carbon dioxide diffuse into the leaf
They are thin- there is a short distance for the carbon dioxide to diffuse into the leaf cells
They have a network of veins- to support the leaf and transport water and carbohydrates
What are some features of the xylem?
- they have VESSELS MADE OF DEAD CELLS
- the vessels have lignified cell walls
- the end walls disappear completely
- they have pits
- they TRANSPORT WATER THROUGH THE PLANT
What are some features of the phloem?
- the ELEMENTS ARE MADE FROM LIVING CELLS
- they don’t have lignified cell walls
- the end walls form sieve plates
- no pits (plasmodesmata)
- they are where the TRANSLOCATION OF GLUCOSE happens
How does the xylem work?
In the xylem, water is absorbed from the soil through root hair cells and transported through the xylem vessels up the stem to the leaves. Water then evaporates from the leaves (transpiration) sometimes.
How does the phloem work?
Phloem vessels are involved in translocation. This is the movement of food substances from the stems to growing tissues and storage tissues.
What is transpiration?
It explains how the water moves up and down a plant without gravity. Water evaporates and then diffuses out of the leaf. Xylem cells make a continuous tube and produce a flow of water and dissolved minerals from roots to leaves.
What do factors that speed up transpiration also increase?
The rate of water uptake from the soil. So, if water is scarce or the roots of a plant are damaged, it increases a plants chance of survival if the transpiration rate can be slowed down. Plants do this by wilting.
How and why is a plant adapted for transpiration? (6)
- A healthy plant must balance its water loss from leaves with uptake through roots. Water is used for cooling, photosynthesis, support and the movement of minerals
- The waxy cuticle on some leaves and small number of stomata on the upper surface so if a plant loses too much water they stop it from becoming flaccid. There are lots of root hair cells too.
- The guard cells provide a way to reduce excessive water loss
- The leaf is flat and thin to allow water loss
- If there is lots of light and water, the chloroplasts make sugars at a high rate, the water enters the guard cells by osmosis, guard cells become turgid and the stomata opening gets bigger
How does light affect the rate of transpiration?
In bright light, transpiration will increase. This leads to an increased rate of photosynthesis as the stomata open to allow more carbon dioxide in so that water diffuses out of the leaf.
How does temperature affect the rate of transpiration?
In higher temperatures, transpiration will increase. This is because the molecular movement increases so that more water molecules evaporate from the cell surface- the rate of diffusion and evaporation of water molecules from the leaf is increased.
How does wind affect the rate of transpiration?
When there is more wind, transpiration will increase. The wind removes water vapour from leaf surfaces so more water diffuses from the leaf.
How does humidity affect the rate of transpiration?
When it is more humid, transpiration will decrease. The humidity increases the concentration of water molecules outside the leaf so diffusion of water from the leaf slows down as the leaf is already surrounded by moist air.
What is the equation for photosynthesis?
Carbon dioxide + water = glucose + oxygen
6CO2 + 6H2O = C6H12O6 + 6O2
What is photosynthesis and how can we measure the rate of it?
Photosynthesis is an endothermic process. We can measure the rate of it by measuring how much sugar/ oxygen is produced over time.
Why would the rate of photosynthesis be important to a farmer?
The farmer would want to find out how they could get the highest rate of photosynthesis so their plants could grow the most and they could have the highest crop yield.
What are the 5 factors that affect the rate of photosynthesis?
- light intensity
- carbon dioxide concentration
- temperature
- amount of chlorophyll
- water supply
How does photosynthesis change with light intensity/ temperature and carbon dioxide concentration?
When a light gets brighter, photosynthesis increases by only up to a point. When a certain light intensity is reached, the rate of photosynthesis stays constant. Carbon dioxide and temperature follow a similar pattern. Carbon dioxide does not become a limiting factor until later than light intensity so light intensity is more often a limiting factor.
What is a limiting factor?
Any factor that slows down the rate of photosynthesis if there is not enough of it. It is a limiting factor as it limits the reaction from taking place even if the other reactants are in plentiful supply. If a factor like the amount of light or raw material is in short supply, photosynthesis will not happen as fast as it can.
How can you maximise plant growth in a greenhouse?
- add removable netting to dim down the intense light of summer
- add electric lighting to increase light in autumn and winter
- add ventilation vents and a heater to control temperature
What are the limiting factors of the amount of carbon dioxide in the air?
- competition from other plants
- how much respiration is occuring
