● `color{brown}("Xylem")` functions as a `color{violet}("conducting tissue")` for water and minerals from roots to the stem and leaves.
● It also provides `color{violet}("mechanical strength")` to the `color{violet}("plant parts.")`
● It is composed of four different kinds of elements, namely, `color{violet}("tracheids, vessels, xylem fibres")` and `color{violet}("xylem parenchyma.")`
● `color{violet}("Gymnosperms")` lack vessels in their `color{violet}("xylem.")`
A. `color{green}("Tracheids:")`
● `color{brown}("Tracheids")` are `color{violet}("elongated")` or `color{violet}("tube")` like `color{violet}("cells")` with thick and `color{violet}("lignified walls")` and `color{violet}("tapering ends.")`
● These are `color{violet}("dead")` and are without `color{violet}("protoplasm.")`
● The `color{violet}("inner layers")` of the `color{violet}("cell walls")` have thickenings which vary in form.
● In `color{violet}("flowering plants, tracheids")` and `color{violet}("vessels")` are the main `color{violet}("water transporting elements.")`
B. `color{green}("Vessels")`:
● `color{brown}("Vessel")` is a `color{violet}("long cylindrical tube")`-like structure made up of many cells called `color{violet}("vessel members,")` each with `color{violet}("lignified walls")` and a large central cavity.
● The `color{violet}("vessel cells")` are also devoid of `color{violet}("protoplasm.")`
● `color{violet}("Vessel members")` are interconnected through perforations in their common walls.
● The presence of `color{violet}("vessels")` is a characteristic feature of `color{violet}("angiosperms.")`
C. `color{green}("Xylem Fibres:")`
`color{brown}("Xylem fibres")` have highly `color{violet}("thickened walls")` and obliterated central lumens.
● These may either be `color{violet}("septate or aseptate.")`
D. `color{green}("Xylem Parenchyma:")`
● `color{brown}("Xylem parenchyma")` cells are`color{violet}(" living")` and `color{violet}("thin-walled, ")` and their cell walls are made up of `color{violet}("cellulose.")`
● They store `color{violet}("food materials")` in the form of starch or fat, and other substances like `color{violet}("tannins.")`
● The `color{violet}("radial conduction")` of water takes place by the ray `color{violet}("parenchymatous cells.")`
E. `color{green}("Types of Primary Xylem:")`
● Primary xylem is of two types – `color{brown}("protoxylem and metaxylem.")`
● The first formed `color{violet}("primary xylem elements")` are called `color{brown}("protoxylem")` and the later formed `color{violet}("primary xylem")` is called `color{brown}("metaxylem.")`
`star` `color{green}("Endarch:")`
● In stems, the `color{violet}("protoxylem")` lies towards the centre (pith) and the `color{violet}("metaxylem")` lies towards the periphery of the organ.
● This type of `color{violet}("primary xylem")` is called `color{brown}("endarch.")`
`star` `color{green}("Exarch:")`
● In `color{violet}("roots, the protoxylem")` lies towards periphery and `color{violet}("metaxylem")` lies towards the centre.
● Such arrangement of `color{violet}("primary xylem")` is called `color{brown}("exarch.")`
● `color{brown}("Xylem")` functions as a `color{violet}("conducting tissue")` for water and minerals from roots to the stem and leaves.
● It also provides `color{violet}("mechanical strength")` to the `color{violet}("plant parts.")`
● It is composed of four different kinds of elements, namely, `color{violet}("tracheids, vessels, xylem fibres")` and `color{violet}("xylem parenchyma.")`
● `color{violet}("Gymnosperms")` lack vessels in their `color{violet}("xylem.")`
A. `color{green}("Tracheids:")`
● `color{brown}("Tracheids")` are `color{violet}("elongated")` or `color{violet}("tube")` like `color{violet}("cells")` with thick and `color{violet}("lignified walls")` and `color{violet}("tapering ends.")`
● These are `color{violet}("dead")` and are without `color{violet}("protoplasm.")`
● The `color{violet}("inner layers")` of the `color{violet}("cell walls")` have thickenings which vary in form.
● In `color{violet}("flowering plants, tracheids")` and `color{violet}("vessels")` are the main `color{violet}("water transporting elements.")`
B. `color{green}("Vessels")`:
● `color{brown}("Vessel")` is a `color{violet}("long cylindrical tube")`-like structure made up of many cells called `color{violet}("vessel members,")` each with `color{violet}("lignified walls")` and a large central cavity.
● The `color{violet}("vessel cells")` are also devoid of `color{violet}("protoplasm.")`
● `color{violet}("Vessel members")` are interconnected through perforations in their common walls.
● The presence of `color{violet}("vessels")` is a characteristic feature of `color{violet}("angiosperms.")`
C. `color{green}("Xylem Fibres:")`
`color{brown}("Xylem fibres")` have highly `color{violet}("thickened walls")` and obliterated central lumens.
● These may either be `color{violet}("septate or aseptate.")`
D. `color{green}("Xylem Parenchyma:")`
● `color{brown}("Xylem parenchyma")` cells are`color{violet}(" living")` and `color{violet}("thin-walled, ")` and their cell walls are made up of `color{violet}("cellulose.")`
● They store `color{violet}("food materials")` in the form of starch or fat, and other substances like `color{violet}("tannins.")`
● The `color{violet}("radial conduction")` of water takes place by the ray `color{violet}("parenchymatous cells.")`
E. `color{green}("Types of Primary Xylem:")`
● Primary xylem is of two types – `color{brown}("protoxylem and metaxylem.")`
● The first formed `color{violet}("primary xylem elements")` are called `color{brown}("protoxylem")` and the later formed `color{violet}("primary xylem")` is called `color{brown}("metaxylem.")`
`star` `color{green}("Endarch:")`
● In stems, the `color{violet}("protoxylem")` lies towards the centre (pith) and the `color{violet}("metaxylem")` lies towards the periphery of the organ.
● This type of `color{violet}("primary xylem")` is called `color{brown}("endarch.")`
`star` `color{green}("Exarch:")`
● In `color{violet}("roots, the protoxylem")` lies towards periphery and `color{violet}("metaxylem")` lies towards the centre.
● Such arrangement of `color{violet}("primary xylem")` is called `color{brown}("exarch.")`