Adaptations for Transport: Plants Flashcards
How are water, mineral ions and organic molecules transported in plants?
In two separate transport system
How many transport systems do plants have?
2 separate transport systems
Why are water and mineral ions transported?
(Transport of water and mineral ions
They are needed by photosynthetic cells
Where are water and mineral ions only available? (transport of water and mineral ions)
In the soil
How are water and mineral ions transported?
transported upwards in hollow tubes (formed by dead cells) called xylem tissue
what is the glucose produced during synthesis used to make? (transport of the products of photosynthesis)
The glucose produced during photosynthesis is used to make sucrose and amino acids (photosynthates)
What are of photosynthates?
sucrose and amino acids
How are the products of photosynthesis transported?
(bi-directional movement)
-These molecules must be moved from the leaves to other organs of the plant (e.g. roots and flowers/fruits/shoot tips)
-The photosynthates are transported upwards and downwards in phloem tissue (bi-directional movement)
what is the distribution of vascular tissue (xylem and phloem) in stems, leaves and roots?
The distribution differs
What is a distribution of vascular tissue in the leaf?
-Leaf has a vascular bundle arranged as a vein or midrib
what does the arrangement of the vascular bundle give the leaf?
this gives flexible strength and resists leaning strain
What are the features of a leaf?
-Cuticle
-Upper epidermis
-Palisade mesophyll
-Spongy mesophyll
-Lower epidermis
-Stomata
-Guard Cells
-Xylem and phloem (vascular bundle)
what is the distribution of vascular tissue in the stems?
vascular bundles arranged around the periphery of the stem
What does the arrangement of the vascular bundles in the stem provide it with?
Provides flexible support and bending strain
What are the functions the vascular bundles in the stem?
-Acts as a site for storage
-provide storage support for the plant
-Provide transportation between roots and leaves
What are the features of a stem?
-phloem and xylem (vascular bundles)
-Cambium
-Pith
-epidermis
-cortex
what is the distribution of vascular tissue in the root?
-Vascular tissue arranged in the centre of the root and together with the endodermis, and the pericycle is called the stele; there are no vascular bundles in the root
What are the functions of the vascular tissue in the root?
-anchors the plant
-Absorb water and mineral ions from the soil
-Act as a site for food storage
-Provides resistant to vertical strain
what are the features of the root?
-epidermis
-Root hair
-Cortex
-Stele (containing xylem and phloem)
-endodermis
-pericycle
how are mineral ions transported (roots)?
-mineral ions such as nitrates are actively transported from the soil into the root hair cells.
what do the mineral ions being actively transported from soil to root hair cells do? (roots)
-This lowers the water potential inside the root hair cells so water enters by osmosis
Why does oxygen enter the roots and what does it provide?
-Oxygen enters the roots from the soil to be used in aerobic respiration, providing ATP for active transport
what do waterlogged soils lack and what does this cause?
-Waterlogged soils, lack oxygen and so plants struggle with uptake of ions in these environmental conditions
what do water and dissolved mineral ions travel through? (uptake of water and mineral ions into the xylem)
the root cells of the cortex to the epidermis down a water potential gradient
what does transport of water across the route occur by? (uptake of water and mineral ions into the xylem)
the symplast appoplast and vascular roots
what is the Apoplast pathway?
-what is taken up by the root hair sale and moves across the cortex by cohesion via cell walls
what is the symplast pathway?
-water moves from the cytoplasm of one cell to the next by osmosis via plasmodesmata
What is the vacuolar pathway?
-water can move via the cytoplasm and vacuoles
what is the process of the uptake of water and mineral ions into the xylem?
The cell walls of all the endodermal cells contain a Casparian strip made of a waxy substance called suberin that is impermeable to water molecules and mineral ions, meaning the apoplast pathway is blocked at this point.
Water and mineral ions from the apoplast pathway are forced across the cell membrane into the symplast pathway.
Active transport is needed to move ions into the cytoplasm of the endodermal cells. Mineral ions then diffuse into the pericycle and then into the xylem.
Therefore, the only way that water and mineral ions can pass through the endodermis to the pericycle and into the xylem is by the symplast pathway.
Water follows by osmosis, down a water potential gradient.
This gives the plant greater control over which ions enter the xylem and are transported to the rest of the plant.
What is root pressure?
-when water moves from the endodermal cells of the root and into the xylem by osmosis this generates hydrostatic pressure and forces water a small distance up the xylem
With reference to role of the casparian strip, how would cyanide result in the reduction in root pressure?
-Casparian strip stops apoplast pathway, so forces ions into symplast pathway
-movement of ions into xylem requires active transport
-Cyanide is a respiratory inhibitor so prevents cells inspiring and stops ATP synthesis
-so lower water potential gradient reduces movement of water in by osmosis thus lowering the root pressure
why does the plant need to control entry of mineral ions into the xylem?
-some minerals are toxic if they are absorbed they can accumulate inside plant tissues (e.g. copper ions)
how does the plant ensure toxic ions cannot enter its cell?
-there are no carrier proteins specific to these ions on the membrane, so these ions cannot enter by facilitated diffusion.
Why do plants need to absorb nitrates from the soil?
required for synthesis of amino acids, proteins, DNA, RNA, ATP, nucleotides, nitrogenous bases
-what are some other mineral ions, absorbed by plants
-potassium ion
-Calcium ion
-Phosphate ion
-Magnesium ion
What are potassium ions required for?
required for stomatal opening
What is the use of calcium ions?
Constituent of cell walls
What is the use of phosphate ions?
Synthesis of phospholipids constituent of ATP
What is the use of magnesium ions?
Constituent of chlorophyll
what are two features of the root hair cells that are adaptations for uptake of water and mineral ions?
-Large SA for absorption of water and mineral ions
-Large numbers of mitochondria (ATP required for active transport of ions)
What is the definition of transpiration?
-transpiration is the evaporation of water from inside the leaves through the stomata and into the atmosphere.
What is the process of a transpiration stream?
-water is absorbed by the root hair cells
-water moves through the root tissue, into the xylem and is transported up the xylem in the plant stem to the leaf
-water is transported by osmosis from the xylem in the leaf to the cells of the spongy mesophyll, where it evaporates from the surface of the cells into the airspaces
-Water vapour then diffuses from the airspaces out of the leaf through the stomata down a water potential gradient
What is cohesion?
-water molecules are attracted to each other by hydrogen bonds
What is adhesion?
water molecules are attracted to the hydrophilic lining of the lignified xylem vessel walls
How does water travel up the xylem to the leaves of the plant?
The cohesion-tension theory (transpiration pull)
What is the cohesion tension theory?
-as water vapour diffusers out of the stomata of the leaf by transpiration, water molecules are drawn up from behind to replace those lost
Water molecules are drawn across the leaf up to the xylem
-This is possible because of cohesion between water molecules due to hydrogen bonds and adhesion between water molecules and the xylem vessel walls
-This upward movement of water creates tension on the xylem vessel walls
what are two other processes that help water move up the xylem a small amount?
-capillarity
-Root pressure
What is capillarity?
-The forces of adhesion and cohesion allow water molecules to rise up narrow tubes for a short distance, which is useful in small plants.
Why is capillarity not useful in large trees?
After a short distance, capillary action is opposed by gravity
What type of plant does root pressure have more effect in?
Small plants
What increases the rate of transpiration?
Any factor that increases the water potential gradient between the water vapour in the leaf and the surrounding atmosphere
What factors increase the rate of transpiration?
-increased light, intensity, temperature and wind speed
-Decreased humidity