9 Transport in Plants Flashcards
What are the metabolic demands of plants (transport) (2)
-hormones in plants need transporting
-mineral ions absorbed by the roots need to be transported to all cells
why do plants need a transport system (3)
-metabolic demands
-size = plants don’t stop growing
-surface area = leaves have a large SA:V ratio, but plants overall have a low SA:V ratio
what is the series of transport vessels running through the stem, roots and leaves called ….
The vascular system
what does the xylem carry (2)
-water
-soluble mineral ions
which direction does the xylem carry its items
-upwards , roots to leaves
what does the phloem carry (2)
-sugars
-amino acids
which direction does the phloem carry its items
up + down
from the leaves to the rest of the plant
what are vessels
tubes with thick lignified walls and no cross walls or living cell contents
what does lignin do (6)
-waterproof
-strong
-causes cell death
-prevents tube collapse
-flexible, its shape is a spiral, ringed, broken rings
-water can enter and exit though irregular breaks in the lignin
is the xylem or phloem in the centre
xylem = centre
what are the functions of the pits in xylem (2)
-allow water + solutes to move from the xylem to the cells
-bypass a blockage
explanation for xylem structures + processes (big)
The xylem is lined with lignin which kills of the cells surrounding it. This forms a spiralled column in which the mass flow of water and solutes can be transported in. Bordered pits are on the walls of the xylem and these allow water and solutes to pass from the xylem to the cells. The companion cells are there for loading and unloading sugars into the cavity of sieve tube members.
Explanation for the phloem’s structure + processes
phloem carry ions, water and sugars. The structure is made up of sieve tube elements which are long cells containing no nucleus or cytoplasm. The phloem tissue contains perforated sieve plates, which allow substance’s to pass though.
Hydrostatic pressure in plants is called ……. its caused by ……
turgor pressure
osmosis
what does turgor pressure do
-drives cell expansion
(the force that enables plants roots to force their way through tarmac + concrete)
what is a root hair
a long thin expansion of a root hair cell, a specialised epidermal cell
facts for root hair cells (structures for processes) (4)
-microscopic size = penetrate easily between soil particles
-large SA:V ratio = thousands of root hair cells on root tip
-thin surface layer = diffusion + osmosis can take place quickly
-concentration of solutes in the cytoplasm = maintains water potential gradient between the soil water and the cell.
apoplast pathway
travels through cell walls by cohesion
Symplast pathway
Travels though cytoplasm + plasmodesmata
Vacuolar pathway
travels though the vacuole + plasmodesmata
what is plasmodesmata
- these are almost gaps in cell wall + membrane pf a plant cells when together, for easier paths that water can take (faster)
Casparian strip
-surrounds the endodermis cells
-stops flow in apoplast pathway
( looks like a cube with a dark strip all around its outside)
information card for how water travels from soil to xylem
-Enters root cell via osmosis down the concentration gradient due to the higher volume of minerals inside the cell and a lower water potential than the soil. (active transport maintains the concentration gradient, by taking the mineral ions in)
-Water travels by 3 pathways symplast, apoplast and vacuolar.
- When water reaches the endodermis cells which are surrounded by casparion strips the apoplat pathway no longer works. Water then travels into the endodermis cell by vacuolar and symplast pathways.
-Water now enters the xylem through the endodermis cells.
what does root pressure do
moves water through the xylem
how is root pressure caused
endodermis cells use active transport to take mineral into the xylem, this then lowers the water potential in the xylem causing water to enter. The lower the water potential in the xylem making it more negative.
what is cohesion
water molecules stick together due to hydrogen bonding
what is tension
‘suction’ pulls more water into the leaf
What is adhesion
hydrogen bonds in water stick to cellulose on inside of the cell wall
what us transpiration
the continuous pull of water through a plant
what is capillary action
water will pull adhere to the dies of a vessel and move upwards in confined spaces, caused by the adhesive properties of water.
can observed in glassware, the narrower the glassware diameter the more the water creeps up.
only contributes minimally to overall movement up the xylem
wyas leaves/ plants conserve water (9)
-root adaptations
-thick waxy cuticle
-sunken stomata
-reduced leaves
-reduced number of stomata
-hairy leaves
-curled leaves
-succulents
-leaf loss
why are root adaptations good
can penetrate several metres deep, shallow roots to absorb water before it evaporates
why are sunken stomata good
stomata located in pits, reduce air movement, produce microclimate + collects water that would’ve left
why are hairy leaves good
create a microclimate of still humid hair. Some plants such as marram grass have micro hairs in sunken stomata pits.
why are curled leaves good
Con fines all of the stomata within a microenvironment of still humid air to reduce diffusion of water vapour from the stomata, creates a smaller SA:V ratio e.g. marram grass
structures of hydrophytes (3)
-buoyancy = air spaces
-stomata on the upper endermis, so they are exposed to air for gas exchange
-leaf stem has many air spaces, helps with buoyancy and quick diffusion of oxygen to roots for aerobic respiration.
info card how does water move from a source to a sink (5 steps)
1
Sucrose is actively loaded into the sieve tube element and reduces the water potential
2
Water flows by osmosis and increases the hydrostatic pressure in the sieve tube element
3
Water moves down sieve tube from higher hydrostatic pressure at source to lower hydrostatic pressure at sink
4
Sucrose is removed from the sieve tube by the surrounding cells and increases the water potential in the sieve tube
5 Water moves out of sieve tube and reduces the hydrostatic pressure.
