Question

which of the following elements of xylem lack lignified cell wall ?
1) xylem paremchyma
2) xylem fibres
3) vessels
4) both a and b ​

Answer 1

$\rm \green{xylem \: fibres}$

Answer 2

Answer:

Explanation:

Only living cells of xylem

The cell wall is cellulosic and thin

They have prominent nucleus and protoplast

Cells are colourless and have large vacuoles

Living parenchyma cells are found in both primary and secondary xylem

Fat and storage protein contents of parenchyma cells vary seasonally

Crystal containing parenchyma cells have lignified walls with secondary thickening may be subdivided by septa

In herbaceous plants and young twigs of woody plants, chloroplasts occur in xylem parenchyma cells, particularly in ray parenchyma cells

Both axial and ray parenchyma cells which are present beside vessels form outgrowths called “tyloses”

The parenchyma cells that give rise to tyloses are termed as “contact cells”

Nucleus and cytoplasm of xylem parenchyma cells migrate into tyloses

Tyloses store a variety of substances and may develop secondary walls

Some tylose might differentiate into sclereids