Transport, Food Storage And Gas Exchange In Flowering Plants Flashcards
Give examples of plant metabolisms
Reactions such as photosynthesis, respiration, and reasons that occur in other processes such as cell division, growth and reproduction
To allow processes/reactions to occur, what do plants need?
To acquire and transport water, carbon dioxide, oxygen and certain minerals
What are root hairs?
Extensions of root epidermis cells
Why are root hairs suited to absorption?
They have thin walls and are not covered by a cuticle [which prevents water loss]
Water uptake by roots
Water enters the root hair cells by osmosis. Large number of roots hairs increases the surface area over which absorption can take place. Roots are assisted by the presence of fungal hyphae which do not harm plants but increase the surface area for the absorption of water and minerals by osmosis.
How does water enter the roots by osmosis?
Soil particles enclosed by pure water known as capillary water. The cytoplasm of root hairs contains many dissolved solutes which means it is more concentrated than the water in the soil.
Movement of water into xylem
Water diffuses from root hair cells into ground tissue and it continue to diffuses across tissue until it reaches xylem in centre of root
Xylem vessels form a continuous hollow pipeline from the roots to all parts of the plant. Water can flow in xylem from roots up through stem, into the petiole and from there into the leaves
What two mechanisms cause the movement of water from the roots to the upper parts of the plant
Root pressure
Transpiration
Explain how root pressure causes the upward movement of water
When water is drawn into roots by osmosis, the build up of water causes pressure. Root pressure pushes water up through the xylem
What does root pressure not fully explain?
How water rises in stems, especially in very tall trees. Root pressure has been measured and it is not strong enough to push water to the top of very high plants
What is transpiration?
It’s the loss of water vapour [by evaporation] from the leaves and other aerial parts of the plant
Where does most transpiration take place?
Through openings called stomata on the underside of the leaf
How does transpiration occur?
Water evaporates from ground tissue in the leaf into the airspaces. Then it diffuses out into the atmosphere through stomata. When cells in ground tissue lose water they become less swollen, less turgid and more concentrated than the xylem cells water passes from xylem into ground tissue by osmosis.
How do plants prevent wilting?
Reducing their rate of transpiration
How do plants reduce. Their rate of transpiration?
Leaves have a waxy cuticle which prevents water loss usually thicker on upper surface [more water can evaporate], the cuticle does not cover stomata on the lower surface
Stomata normally located on the lower surface of a leaf which helps reduce water loss because the rate of evaporation is higher on the upper surface
Each stoma is surrounded by two guard cells. The guard cells can open or close the stoma by changing shape. Stomata are open by day which allows the leaf to exchange gases for photosynthesis during the day. At night, they close which helps to reduce water loss from leaves at night
What would cause stomata to close during day?
Plant looses too much water, high temperatures and high wind
Rate of transpiration is so great, by closing stomata it reduces water loss
Give an example of active transport in plants
Entry of minerals into root hair
Requires energy
How is the energy for the entry of minerals supplied?
Contains many mitochondria
Where does photosynthesis take place in the leaf?
Chloroplasts in mesophylls cells
What are the two sources of co2 in plants?
Comes in through stomata from atmosphere - diffuses into air spaces
Co2 produced by respiration may be used for photosynthesis
