Plants have two types of vascular tissue:
- Xylem Tissue
- Phloem Tissue
Xylem tissue is composed of 4 different types of cells:
- vessels - main conducting cells
- Tracheids - secondary conducting cells
- fibres - give support to the structure
- xylem parenchyma - the packing tissue
The role of xylem tissue is to carry water and minerals up through the roots and to the leaves where the water will be used for gas exchange.
xylem also provides mechanical stregnth and structure to the plant.:)
these couldn't give less of a **** about transport. All these bad boys need to care about is supporting the structure of the plants.
They have Thick, lignified walls with narrow lumens as this structure is efficient in keeping the stem straight and upright.
these act as packing tissue to fill up space between the fibres, vessels and tracheids. these are also a sorage medium and allow materials to travels across the xylem tissue with the help of pits in the walls of the vessel segments.
These are made up of vessel segments which have strong lignin walls, just like fibres!
Their lumens are comparitively wide to allow sufficient amounts of water to travel through them.
The xylem is the main transporter of water, but tracheids also transport water up the plant. they are less evolved and more primitive versions of vessels, but still fulfill the same role, just less efficiently.
Transport to the xylem from the roots
to absorb as much water as possible from surrounding soil particles, root cells have evolved 'root hairs' to greatly increase the surface area-increasing the amount of diffusion paths.
plants need to absorb high quantities of water to compensate for waterloss throught the stomatal pores of the leaves.
the entire process by which the roots absorb water is dependant on osmosis.
1. intrinsic proteins in the membrane of the root hair cells draw in minerals from the soil by active transport.
2. now that the water potential inside these cells has dropped, water is drawn into the cell by osmosis.
3. the minerals continue to be drawn into the centre of the root by active transport throughout the cortex (the cells between the root hairs and the casparian *****)
4. the water follows this trend and is drawn towards the xylem.:):):):):)
ITS IN THE ROOTS NOW U DID IT
BUT, now we gotta get the water and minerals to the xylem cells.
Water can travel to the centre of the roots through 3 different pathways.
Now that we've got the water through the cortex, we reach the casparian *****. xylem tissues are surrounded by a single layer of cells called the endodermis. These cells have…