Transport in plants Flashcards
How does transport occur in small organism of aquatic plants?
Movement of water circulates materials past the body of these plants/algae.
Diffusion of substances in/out of the body as in algae etc.
Large SA:Vol ratio allows this to occur.
No internal transport system.
How does transport occur in large organisms of aquatic plants?
If flattened in shape they have no need for internal transport system.
Diffusion of materials in/out will occur.
A high SA:Vol ratio due to flattened, thin shape.
More complex plants (such as sea grasses) have an internal transport system of xylem and phloem.
How does transport occur in small organisms of terrestrial plants?
Live in moist environments or are able to become metabolically active at times when the environment is moist.
Diffusion of substances in/out of the body e.g. mosses and other bryophytes.
No internal transport system.
Large SA:Vol ratio.
How does transport occur in large organisms of terrestrial plants?
Internal transport system
Xylem and phloem – series of tube like structures that transport water, sugars and salts around the plant from the roots to the leaves.
Angiosperms or flowering plants.
Describe the process of transport in large organisms of terrestrial plants. (Xylem and phloem)
The transport of water into the leaf takes place in the xylem.
This evaporates through the stomata.
As water molecules leave the stomata more is drawn up to replace it – a process called transpiration.
Phloem takes away sugars made by the leaf to supply other parts of the plant.
What are 7 structures of a cross section stem?
Epidermis
Cork
Phloem
Vascular bundle
Cambium
Pith
Xylem vessels
What is a vascular bundle in a stem?
Vascular bundle = Xylem + Phloem +Cambium
What does xylem do in the stem?
Xylem carries water and minerals upwards from the roots.
What does phloem do in the stem?
Phloem carries mainly sucrose down from the leaves.
What does Cambium do in the stem?
Cambium is meristematic tissue that actively divides to form new xylem and phloem cells, making the stem thicker and stronger and increasing transport capacity.
What do the cortex and pith to in the stem?
Cortex and Pith are simple parenchyma (packing) cells. They store food and let air circulate.
What does the epidermis do in the stem?
Epidermis is the protective skin of the stem.
What does the epidermal hairs do in the roots?
Epidermis with root hairs, absorbs water and nutrients from the soil. Water enters via osmosis and dissolved ions move in by diffusion and active transport.
What does the cortex do in the roots?
Cortex is made of simple parenchyma cells, stores food and lets air circulate.
What does the Endodermis do in the roots?
Endodermis is the innermost layer of the cortex and controls substances passing into the vascular tissue.
What does the Xylem do in the roots?
Xylem takes water from the surrounding cells and conducts it upwards.
What does the Phloem do in the roots?
Phloem passes sucrose made in the leaves on to the root cells.
What are the 6 structures in a root cross section?
Epidermis
Endodermis
Cortex
Phloem
Xylem
Epidermal hair
What does the Xylem?
Water carrying ‘pipes’ of the plant.
Formed from the empty remains of dead cells.
The end walls of the cells wither away and water passes from one cell to another.
Walls are coated with a woody substance called lignin, which helps support the stem. Lignin is laid down in various patterns.
What is the Transpiration stream?
Water flows through a plant in an unbroken stream from the roots up to the leaves.
The transpiration stream supplies cells with water and minerals from the soil.
Plants can control the rate of transpiration.
What are the 2 things that cause the transpiration stream?
Root pressure
Transpiration
How does Root pressure cause the transpiration stream?
Water from the soil enters the roots by osmosis. This steady inward flow generates a pressure, called root pressure. This pressure can push water a short way up the stem
How does Transpiration cause the transpiration stream?
Transpiration- as the leaf cells lose water by evaporation into the air, more water is drawn out of the xylem vessels to replace it, by osmosis to replace it.
So, a continuous stream of water is drawn through the plant.
What are 4 factors increasing transpiration?
Light – opens stomata;
Heat – causes water to evaporate from the stomata;
Wind – can increase evaporation of water from the stomata;
Dry air (low humidity) – allows water to evaporate from the stomata more quickly.
