Transport In Plants Flashcards
What are the three main reasons why multicellular plants need transport systems?
-metabolic demands
-Size-plants need effective transport systems to move substances both up and down from the top of the roots to the topmost leaves and stems.
-SA:V -plants cannot rely on diffusion alone to supply their cells with everything they need
Name the components of a stem cell?
-Epidermis
-cortex
-phloem
-xylem
-vascular bundle(xylem and phloem)
-parenchyma(packing and supporting tissues)
Vascular bundles are around the edge to give support and strength.
Name the Components of root hair?
-root hair
-exodermis (outer layer membrane)
-epidermis (inner layer membrane)
-endodermis(membrane around vascular bundles)
-xylem
-cortex
-phloem
Vascular bundles are in the middle to help the plant withstand the tugging strains that result as the stems and leaves are blown in the wind
Name the components of a leaf?
-xylem
-phloem
-midrib of leaf
-palisade mesophyll
In the leaves, the midrib of a dicot leaf is the main vein carrying the vascular tissue through the organ.
Structure and function of the xylem?
Function: non living tissue- transports water, mineral ions and supports the plant.
The xylems flows from the roots to the shoots and leaves.
Structure: long hollow tubes made by dead cells fused together- cell wall has been broken down.
Thick walled parenchyma packs around the xylem vessel- storing food and tanning deposits.
Lignified secondary walls that provide extra mechanical strength- is in the form of the rings, spirals or solid tubes with lots of small unlignified areas called bordered pits(where water leaves the xylem).
Structure and function of phloem?
Function: a living tissue- transports food as organic solutes around the plant from the leaves where they are made by photosynthesis.
Supplies the cells with sugars and amino acids needed for cellular respiration.
The phloem flows both up and down the plant.
Structure: sieve tube elements which a formed together to form a long tube- the walls are perforated to form sieve plates.
Companion cells (linked to the sieve tube elements)- very active cells.
What is transpiration?and what is the transpiration stream?
Transpiration is the loss of water vapour by evaporation through the stomata.
Water enters the roots by osmosis and is transported up by the xylem until it reaches the leaf- at the leaf it moves by osmosis accros membranes and by diffusion From the stomata to outside the leaf
What are the factors that effect transpiration?
Light: the higher light intensity the faster transpiration rate- stomata open in the light so CO2 can enter
Temperature: the higher the temperature the faster the the transpiration rate- warmer water molecules have more energy so evaporate faster out of the leaf. Increases water potential gradient, water diffuses out of the leaf faster
Humidity: the lower the humidity the faster the transpiration rate. If air around the leaf is dry, the water potential gradient between the leaf and air is increased.
Wind: the windier the faster the transpiration rate air movement blows away water molecules from around the stomata- increasing water potential gradient
Availability of water: if there is less water ability in the soul, then the plant cannot replace the water that is lost, therefore plant will wilt as will have lost too much water.
What is adhesion and cohesion?
Adhesion is when water molecules form hydrogen bonds with the carbohydrates in the walls of the xylem vessel.
Cohesion is when water molecules form hydrogen bonds with each other so tend to stick together.
Cohesion and adhesion allow water to rise up narrow tubes against gravity.
What is the apoplast pathway?
Water moves through the spaces between cell walls - does not pass through any plasma membrane so can calmly dissolved mineral ions and salts
What’s is the symplast pathway?
Water passes through the cytoplasm and plasma membrane and pass from one cell to another through the plasmodesmata.
