B4 Plant part Flashcards
What are plant tissues?
Collections of cells specialised to carry out specific functions.
What is the epidermal tissue?
It covers the surface of the plant and protects it. It often secretes a waxy tissue
What is the palisade mesophyll tissue?
Contains lots of chloroplasts, which carry out photosynthesis.
What is a spongy mesophyll tissue?
Contains some chloroplasts for photosynthesis but also has large air spaces and a large surface area to make the diffusion of gases easier.
What do the xylem and phloem cells do?
The xylem cell carries water and dissolved mineral ions from the roots and around the plant and into the leaves. The phloem carries dissolved food from the leaves and around the plant.
What do the plant organs do?
The specialised tissues are arranged to form organs, which carry out their own particular functions. The leaves, stems and roots are all plant organs which all have specific jobs.
Phloem in depth:
The phloem tissue transports the sugars made from photosynthesis from the leaves to the rest of the plant. This includes transport to the growing area of the plant. It is also transported for storage.
How does the phloem cell use translocation?
The phloem is a living tissue so the cells are alive. This means the movement of dissolved sugars from the leaves to the rest of the plant is called translocation.
Xylem in depth:
The second transport tissue in the plant, which carries water and mineral ions from the soil around the plant to the stem and the leaves. They are dead cells.
How can you test for xylem cells?
You can demonstrate the movement of water by putting celery into food colouring. After a few hours when you cut into the stem you will see coloured circles where the water and dye has moved through the xylem.
Why is transportation so important?
It is vital food is made by photosynthesis and transported, as it can cause areas to die. The mineral ions are also needed for the production of proteins and other molecules. The plant needs water for photosynthesis and to hold itself upright.
What are the stomata?
Small openings for air to be allowed in, carbon dioxide diffuses into the air spaces and into the cells. At the same time oxygen diffuses into the surrounding air, maintaining a concentration gradient. The size of the stomata is regulated by the guard cells.
What is transpiration and the transpiration stream?
This can cause a loss of water vapour which evaporates from the cells lining the air spaces and passes out of the leaf due to diffusion. The loss of water vapour is called transpiration. As water evaporates, more water is pulled up through the xylem to take its place, this movement is called the transpiration stream.
What can affect the rate of transpiration?
Different conditions, such as temperature, humidity, and the amount of air movement. An increase in the rate of photosynthesis due to the stomata opening for diffusion but then water vapour evaporating. Windy conditions can steepen the concentration gradient by removing water as it diffuses out.
How can plants maintain water loss?
Most plants have a waxy cuticle to prevent it, and the stomata is on the bottom so it protects the leaves from direct light and energy of the sun. The plant may wilt which reduces the surface area available for water loss by evaporation. The stomata also could close, which stops photosynthesis and may cause overheating.
