Chapter 9 Transport In Plants Flashcards
Give 3 reasons why transport system is needed in plants?
1) to match metabollic demands in all cells (from roots to leaves)
2) to transport to potentially huge sizes of plant (like tall trees ) need effiecent shstems to move up and down
3) SA:V is not constant in a plant, good at leaves but nit in trunks roots etc, where only simple diffusion would not be effeicent enough to sustain metabollic demands
Explain the first reason “each cell needs to be able to have access to all sushatnces for metabollic demands” (3 you can say)
- each cell needs a certsin amount of substance to carry out metabollic demand. Leaves are able to make glucose and oxygen but the roots cant, so a transport system is needed here, and for waste products tinbe removed (they cant donit).
- Or roots absorb mineral ions and these need to be transported to every cell, so proteins and enzymes can be made in cell structure etc
- even normal hormones that are made in ine part of the plant may need to go to the other part and so a transport system is needed here
Deacribe the structure of a leaf in a plant in layers
Where are the stomata
What is mesophyll?
Why are spongy mesophyll cells needed?
- waxy cuticle
- upper epidermis
- palsaide (mesophyll) cells
- spongy (mesophyll ) cells
- lower epidermis (here the stomata with guard cells are)
- waxy cuticle too
2) mesophyll refers to middle of leaf
3) spongynis important as these create air spaces which allows for more surface area for gas exchange to take place in to the cells that will photosynthesise
What is a dicotyledonous plant
What is a cotyledon
A dicot is a plant that makes seeds that contain two cotyledons
- these are organs that act as food stores for thr developing embryo plant and form the first leaves of the plants when they germinate
What are the two types of dicots and which one do we need to know about (what sre basic features that distinguish them)
Need to know about HERBACEOUS DICOTS!
- sift tissues which die at thr end of the growing season
woody dicotd (aborescent) - hard lignifnied tissues and a long life cycle
How are the vascular bundles in herbaceous dicots arranged differently in stems leaves and roots?
- first in general the xylem is the inner more and phloem outer more
1) stem = on the outside in a ring like fashion to give support
2) roots = in the middle star shaped
3) leaves = midrib of a dicot leaf is the main vein carrying the vascular tiddue , but there are also many small branching veins spread through the leaf for transport and support
Explain why the vascualr bundle is where it id in roots stem leaf
Speaking of veins in leaf how dontou describe this
- in stem around outside in ring like to give support
- in roots in middle in star shape, and this helps withstand TUGGING STRAINS that resultnas the stems and leaves are blown in the wind
- in the leaves just ij the midrib as the main vein , this acts as support and provided structure to leaf. With many veins branching out that help in support and function, it also acts as support too.
2) VENATION IS NETTED RATHER THAN LONG AND NARROW (eudicot )
Some basic differences between dicots and monocots
Main featured first
- Dicotd = two cots vs one
- Venation in dicot is netted vs straight and narrow
- Petals in dictonim in 4s or 5s compared to 3s in monocots
(You know vb in stem is rung on outside for support, however in stem of monocot scattered)
(You kniw vb in roots is star like in the middle for support, but in monocot in ring )
Function and structure of xylem
- vessels and how they made
- in between? What does this have
- (what is tannin)
- where does water leave
Function = to transport water and mineral ions one way upwards + support of the plant
Structure =
- made up of several types of dead cells that form the xylem vessels
- these have no end cell walls and then cells fused to make a continous hollow tube
- these also are STRENGTHENED by lignin secondary walle for extra meschnical strentgh
- in between vessels are xylem PARENCHYMA which store food and contain tannin
- tannin is bitter chemical thwt protects plants from herbivores
2) watwr leaves through non lignified pits
Function of phloem
Function : to tranport food in the form of orgsnic solutes around thr plant from lesves where they are made by photosythenis
Features and structure of phloem
What extra do they have , what reduces resistance and obstruction
- transport can be both up or down
- made from living cells also joined end to end to form a continous hollow tube , NO LIGNIN
- in between each end wall the end walls have perfoatednholes called sieve tube plates, this REDUCES RESISTANCE of solute movement making it easier to go
- most of cell components are broken down and lost to REDUCE OBSTRUCTION
- as a resukt there are often COMPANION cells attached to a sieve tube element with a cinnected plasmidesmata to allow for rapid transfer of substance. This cell carriees out all life functions for itself and the sieve tube element
Similarities and differences quick between xylem phloem
Xylem = dead, phloem alive Xylem = end to end walls to make hollow, phloem = yes Xylem = no nuclues , phloem too Xylem = lignin = phloem = no Xylem = one way , phloem = both ways Xylem = no end walls , phloem = perfosted holes in them
How to observe vascular bundle particularly xylem in tissue?
More on celery= which is longtidunal but rhubarb which was trnasverse
1) for example cellery stem cut horizontally to make as thin circles as possible (vb should be on outside )
2) leave in water then stain in TOLUIDINE BLUE
3) rinse srain and put to slide with water
- yiu should be able to see both xylem (inner ) and phloem
But for rhubarb
1) lick a few out and lush apart , add a drop of kethylene bluen
- get excess out, put drop of glycerol snd view
- here yiu should seenthem straight lines woth rings (this is the lignin!)
Why is water so importsnt for plants
- metabolism / function + structure
STRUCTURE AND METABOLLISM
Structure
- tugor pressure provides a hydrostatic skeleton to support the stems and leaves
- DRIVES EXPANSION , ALLOWS ROOTS TO FORCE WAY THROUGH TARMAC AND CONCRETE
Function + metabolism
- helps carry mineral ions
- cools plant down due to having high latent heat when evaporates
- needed for photosynthesis
Water enters the plant through the root hair cells, how are they adapted for this? (4)
They have root haire which is a long thin extension on the cell
- these are microscopic size means they can penetrate easily between soil particles
- each has large SA:V and thousands on each cell
- thin surfsce layer (just cell wall and membrane), small distance = effeicent diffusion
- HIGH CYTOPLASMIC SOLUTE CONCENTRATION in cell ensured perfect potential bradient
How do the root hair cells maintsin this low water potential on the inside? (2)
Explain by water potnials and concentration of soluted in bith media still
- they use active transport in proton pumps to create this and ACTIVE TRANSPORT of mineral ions into the soil makes this lower
- also vacuole takes a lot of the water which lowers water potenial of the cell
As soil has low solute conc, the water potential of it will be high and water thus koves in by osmisis
Once the water has moved into the root hair cell what happens nexr?
Water can then move from cell to cell to the xylem in two ways
- apoplast (cellulose )
- sympkast (cytoplasm)
Describe the symplast pathway to the xylem
What is soil solution
Symplast= simple = cytoplasm
- soil solution moves through a CONTINOUS cytoplasm of cells that is connected through the plasmodesmata by osmosis
- due to the next cell having a lower water potential , water moves from high to low this way snd keeps moving cell by cell until it reaches xylem
- the fact that once water oeaves the root hair cell water potenial is low again which maintains steep conc gradient between spil and cell —> water can then continue to move in by osmosis.
2) soil solutionnis mixture of everything dissolved in water until thr endodermis
Describe apoplasy pathway to the xylem
- movement of soil solution through intracellular spaces of cellulose cell wall
- solution fills these spaces up
- as water is puller into the xylem the pull from this and the Cohesive forces creates a tension that pulls the water across the cellulose fibres
- the fibres offer no resistance and so water can move, by apoplast
What happens once the water reaches close to the xylem (endodermis)
Why is this so necessary
1) water has moved by both apoplast and symplast cell by cell until it reaches a band of cells surrounding the xylem and phloem called the ENDODERMIS
2) Endodermis has a band called the CASPARIAN STRIP- this is a band of waxy material called SUBERIN that forms a waterproof layer around the endodermis
3) water coming by the APOPLAST pathway is blocked by the casparian strip and thus water is forced to join the SYMPLAST pathway
4) in doing so it passes throiugh selectively permeable cell surface membranes, which blocks any POTENTIALLY TOXIC SOLUTES FROM REACHING LIVING TISSUE
Now plant is protected from any danger, if not there accumlated so much over time and cause diseasE
What else does the endodermis ensure?
It ensured any solutes that have accumulated into thr xylem dont go back into the water solution and get wasted.
How does water enter the xylem for the first time (mechanism)
Apoplast or symplast?
What does active pumping of solute create? When is this useful etc snd what else
- the cytopladm of endodermal cells have low solute concentration anyways but
- solutes are actively pumped in towards the xylem
- this means xylem has low water potenial but endodermal high
==and this increases the amount of osmosis happening and water through - at this point its still just SYMPLAST
This creates root pressure and this gives water a bit of s push to the xylem - HOWEVER THIS IS NOT THE MAIN FACTOR OF WATER MOVING TO THE XYLEM.. It is independent of transpiration and can be thought as a helping factor for when say in the night when trsnspirstion stops something still needs to help push the water up .
What FOUR piece of evidence shows a role of active transport for creating root pressure?
1) poisons like cynaide that affect the mitochondria (enzymes ) required for respiration put in soil—> no ATP could be made so no active transport could happen —> root pressure fell
2) root pressure increases with a rise of tempertaure and falls with a lower —> suggesting chemical process (and thus active) is involved (like ensyme optimum reaching)
3) A fall of oxygen or respiratory substances equalled a fall in root pressure
4) GUTTANATION happening
