3.3 Transport In Plants Flashcards
what are the 3 attributes of dicotyledonous plants
- Have 2 seed leaves
- Leaf veins form a net pattern
- Vascular bundle in a diffinite ring
what are the 3 needs for TS
Metabolic demands: Not all cells carry out photosynthesis. Mineral ions absorbed by roots need to be transported to all cells to make proteins. Hormones made in one part of the plant may need to be transported.
Size: Some plants are very large as they continue to grow. This means effective transport systems are required to carry substances great distances.
Surface area to volume ratio: Due to adaptations of leaves, they have high surface area to volume ratio, but many components like trunks lead to lower surface area to volume ratio, which means it can’t rely on diffusion to supply substances to cells
what is a vascular system
Dicotyledonous plants have a series of transport vessels running through the system e.g. roots, leaves, stems
what are vascular bundles
there are two main types of transport vessels, which are arranged together to make a vascular bundle. They are Phloem & Xylem Vessels
where are the vascular bundles found in the stem and what is the arrangement
- Vascular Bundles are found around the edge to give strength & support
- The Xylem in on inside while Phloem is on outside
where is the vascular bundle located in a leaf and what is the arrangement
- above Midrib of the leaf which helps carry vascular tissues through the organ & help support the structure
- Xylem is above the Phloem
Where is the vascular bundle in root locates & what is the arrangements
- The Vascular arrangement is located in the centre to help withstand forces
- Xylem is in the centre and is a cross shape while the phloem is found around the Xylem vessel
what does xylem vessel do
Transports dissolved mineral and water ions and provides structural support.
what 4 tissues are found in xylem vessels
- Vessels
- Tracheid
- Parenchyma
- Fibres
what are the qualities of vessels
Long hollow tubular cells to form hollow structure, joined end to end with perforated plates in between. The lignification of this can be reticulate or spiral, which gives some flexibility in the vessels.
what are the qualities of Tracheids
Elongated cells with lignified cell wall. Mature cell walls are dead an empty. The pits allow rapid transport of water from 1 cell to another.
what are the qualities of Parenchyma
Packs around Xylem vessels which store food and contain tannin deposits, which has bitter taste to protect it from herbivores.
Qualities of Xylem vessel fibres
Long lignified cells which don’t transport water but provide mechanical strength and support. There are pits in the woods to allow water to leave. The lignified cell walls provide mechanical strength but causes cells to be killed.
what is lignification and the new structure
Lignin is deposited into cell wall to make them waterproof while killing the cells and causing the contents to decay, forming a long column of dead cells. These are useful as they prevent the collapse of Xylem as they strengthen the vessels.
what is the outward physical appearance of lignin
Formed in patterns like spirals, rings, or reticulate shapes and allow some flexibility in the stem and branch.
what does phloem do
Transports assimilates from source to rest of plant and transport amino acids.
Sieve Tube Elements
Elongated cells end to end to form a tube have lost most of their organelles, leaving more space to flow of molecules. The end walls have perforations called sieve plates which allow sub to move to the next cell then layer of cytoplasm in the cell wall.
Companion Cells
Form with sieve tube elements, contain small cells and a large nucleus and then cytoplasm. There are many mitochondria from active cells to provide energy required to load and unload sucrose into and out of thief tube elements. Linked to the sieve tube element by Plasmodesmata which links the two cells together.
what 3 adaptations allow for water to move into roots
- Each RHC has high SA:V
- Each hair has a thin surface layer through which diffusion & osmosis can happen quickly
- Concentration of solutes in cytoplasm of RHC maintain the water potential gradient between soil & cell
what is the Symplost Pathway
Water in cytoplasm moved into other cell cytoplasm which are connected by plasmodesmata via diffusion. This pathway is driven by water potential gradient as water moves from root hair cells which have constant supply of water from soil causing increase water potential in her cell allowing it to travel to plant cells via osmosis. In addition, the next adjacent plant cell has lower water potential than current one, allowing for water to be constantly transported forward. This pathway is much slower as there is higher resistance due to organelles.
Apoplast Pathway
Water moves within cells and spaces between the cell walls. Cellulose cell wall has relatively open structure allowing water to move between cellulose fibres. Since water molecules being attracted due to hydrogen bonds via cohesion as water is moved along cells more moves along with it. This pathway is much faster as there is less resistance.
explain movement of water across endodermis
- In endodermis there is a band of waterproof material of waxy suberin called Caparian Strip
- Water can no longer move through the apolost pathway and passes the cell membrane into cytoplasm to become part of S-pathway.
- This allows cell membrane to control which substances can enter Xylem and allows toxins to be filtered out
- Once they pass the strip the water can move back into cell wall
Explain the movement of water into the xylem vessel
Mineral ions are moved into Xylem via active transport. This then reduces water potential in the Xylem. Due to higher water potential and endodermis and lower water potential in Xylem the water moves into Xylem via water potential gradient. This generates root pressure, which pushes up water into Xylem
3 Evidences for the role of Active Transport in root pressure
Some poisons, such as cyanide, affect mitochondria and prevent production of ATP. If cyanide is applied to root cells, there is no energy supply. The root pressure disappears.
Root pressure increases with a rise in temperature an falls with falling temperatures, suggesting chemical reactions are involved.
If levels of oxygen or respiratory substrates fall, root pressure falls.