Plant Transports Flashcards
What are the properties of Monocots
Single Cotyledon,
Long narrow leaf,
Veins are parallel
Vascular bundles scattered
Flower part in multiples of 3
What are the properties of dicots?
Two cotyledons
Broad leaf
Network of veins
Ring of vascular bundles
Flower part in multiples of 5
What is the Casparian strip
thickened with a water-impermeable, waxy suberin layer,
What is the cortext in the plant?
The cortex
-consists of parenchyma cells.
These large, thin-walled cells have leucoplasts to store starch and large vacuoles to store water and dissolved sugars.
Intercellular spaces between parenchyma cells facilitate the movement of water
What is The stele, or vascular cylinder
Consists of the pericycle, phloem, cambium and xylem.
The pericycle is the outermost layer of the stele, and consists of one or more rows of
thin-walled meristematic parenchyma cells. It is in close contact with the xylem and phloem
tissues of the root.
What is the endodermis?
It is the innermost layer of the cortex. It consists of tightly-packed, modified parenchyma cells.
The radial and transverse cell walls are thickened with a water-impermeable, waxy suberin layer, known as the Casparian strip. This layer helps to regulate the flow of water from the cortex into the stele. To aid in directing water, there are also thin-walled passage cells in the endodermis, directly opposite the xylem, allowing water to move into the xylem rapidly.
What is the xylem tissue?
it is responsible for transporting water and
dissolved mineral salts to the xylem tissue of the stem and leaves. These cells are strengthened with lignin for support. The pits in the cell walls allow for the lateral movement of water.
What is Turgidity
Turgidity, or turgor pressure, refers to the water content of cells and how this lends structural support to the plant. When cells absorb water, the vacuoles fill up and the cytoplasm increases, pushing against the cell membranes, which in turn push against the rigid cell walls. This makes the cells rigid, or turgid.
Why is transpiration important for the plant?
Cooling of the plant: the loss of water vapour from the plant cools down the plant when the
weather is very hot.
The transpirational pull: when the plant loses water through transpiration from the leaves, water and mineral salts from the stem and roots moves, or is `pulled’, upwards into the leaves. Water and is therefore taken up from the soil by osmosis and finally exits the plants through the stomata.
Plant structure: young plants or plants without woody stems require water for structural support. Transpiration helps maintain the turgidity in plants.
how does the transpiration pull occur?
Results from the evaporation of water from the surfaces of the mesophyll layer in the leaf to the atmosphere, through the stomata.
What four parts make up the Phloem?
Phloem fibres
Phloem parenchyma
Sieve tubes
Companion cells
What are the two ways water can move through the plant?
Apoplast and Symplast
What is apoplast?
Water moving through the cell wall/intracellular fluid, it is quick but doesn’t have much control due to it being simple diffusion
What is Symplast?
It is when water moves continuously through the cytoplasm, it is very slow but is controllable.
Describe how water moves in and out of the plant.
Water enters the roots via osmosis, then travels through the cells by apoplast or symplast to reach the xylem, then due to cohesion/ the water column being under tension, the water moves up the xylem. Then it enters the leaves where it evaporates and leaves through the stomata.
What are Vascular bundles.
Vascular bundle: bundles of tissue containing
both xylem and phloem
What is th eVacuolar route?
Water passes through tonoplast and then
through vacuoles of cells
What is the Protoxylem?
First xylem to develop behind root and shoot tips; lignin added in rings or spirals
Metaxylem?
More mature, walls fully
lignified
What is the Secondary xylem?
Formed from ring of
cambium
New secondary xylem
formed annually: secondary thickening,
tree rings
Functions of xylem:
Transport
Mechanical strength
What are Tracheids?
Elongated cells with
tapering ends
Not as well adapted as the xylem
Water has to pass
between cells from pit
to pit
Xylem includes fibres
for support and parenchyma as packing
How does Humidity effect
Humidity: increase in humidity reduces water
potential gradient between air spaces and
atmosphere, rate of transpiration decreases
How does wind speed effect
Wind speed: low wind speed, water vapour
accumulates around stomatal pores, reduces
water potential gradient, rate of transpiration
decreases
How does temperature effect
Temperature: increasing temperature,
increasing KE water molecules, increased
diffusion and increase in number of water
molecules that can be held in air, rate of
transpiration increases
How does light effect
Light: indirect effect due to effect on stomatal
opening
What is a Hydrophytes?
Hydrophytes: water plants eg water lily
What is a Xerophytes?
Live under conditions low water availability eg marram grass
What is a Mesophytes?
Live under conditions of
adequate water
Hydrophytes
Roots submerged in mud at bottom of pond and have floating leaves eg water lily
Little or no lignified support tissues (water
supports)
Little xylem
Little or no cuticle on leaves
Stomata on upper surface of leaves
Stems and leaves large air spaces
Reservoir oxygen and carbon dioxide
buoyancy
What are the properties of Xerophytes?
deep roots to reach water far underground
shallow spreading roots to collect occasional
rainfall
leaves reduced to spines with minimum
surface area for transpiration
reduced number of stomata to reduce
transpiration rate
rolled leaves, leaf hairs and stomata sunk in
pits to trap moist air, increasing humidity and
slowing diffusion of water vapour from the
stomata
waxy leaf cuticle which is impermeable to
water (preventing evaporation)
stomata opening at night and closed at
midday when evaporation rate would be
highest (reversed stomatal rhythm).
storage of water in succulent tissues
