xylem ppt

zainab hussaini 12G

does anyone want to guess what the xylem tissues are made out of?

Xylem

Tthey are actually formed from dead cells joined end to end and start off as living tissue

Today we will be learning about: 4.5 know the structure of xylem the position and function of the xylem

Xylem structure

lets get down to the roots of the xylem !

the first xylem the plant makes is called the protoxylem:

• it can streach and grow because the walls arent fully lignified yet
• the cellulose microfibrils are arranged vertically in the stem which increases the strength of the stem and allows it to resist compression force from the weight of the plant

when the cell becomes older increasing amount of lignin is incoperated into the cell wall

• this means that the cell becomes impermeable to water and other substances
• the tissue becomes more stronger and supportive but content of the cell dies
• this lignified tissue is called metaxylem

function of xylem

so how and what does the xylem transport?

• Water and mineral ions are transported from the roots to the leaves and the shoots in the transpiration stream (the movement of water up from the soil through the root hair cells across the root to the xylem across the leaf until it is lost by evaporation from the leaf cells and diffuses out the stomata down concentration gradient).
• water moves out of the xylem into surrounding cells through specialised pits in the walls of the xylem vessels
• the lignified xylem vessels are very strong and help support stem of plants in big ones.

just wanted to quickly touch on this picture in the book as you can see the protoxylem has loads of water in it full of life in the vacuole and has a tranverse plate which divides the planes across the body of a plant but when adding lignin these transverse plates break down and has no living content so no need to seperate

Tell the difference!

jhere is a picture of the protoxylem and the metaxylem as you can see the protoxylem in the middle and smaller whereas the metaxylem is bigger and on the outskirt can anyone suggest why they are bigger?

Question

can you give me 4 differences between the protoxylem and the metaxylem Can you think of any similarities?

solution

Thank You for your attentiveness and time 😊