Plant Stem

Question 1

Function of the plant stem

Answer 1

1) plants with support
2) movement of materials -( water and mineral ions)
3) contain chlorophyll and carry out photosynthesis

Question 2

Parenchyma

Answer 2

Unspecialised plant cells that act as packing in stem and roots to give support

Question 3

Collenchyma

Answer 3

Located outside the stem

Thick primary cellulose walls so they provide strength and flexibility
— living so they stretch with growth

Question 4

Sclerenchyma

Answer 4

Very thick lignified cell walls and an empty lumen with no living content

Have strong secondary cell walls made of cellulose microfibrils positioned at right angle to each other

As the plant grows , lignin is deposited on the cell walls of these fibre in a spiral
—> strong and flexible

When the fibre is lignified , the cell content die because water cannot pass through lignin and so the fibre become hollow tube

Question 5

Explain how xylem is adapted to its function

Answer 5

Content of cells dead

Forming long hollow tubes to carry water

Walls strengthened with lignin to resist forces as water is pulled upwards

Pits to allow some sideways movement of waters

Question 6

Explain the properties of wood

Answer 6

Lignin gives strength but is lightweight

Wood is renewable

Good heat and sound insulator

Composite material

Resist compression forces

Doesn’t crack when cut or nailed and keeps it strength

Question 7

Advantages of cotton

Answer 7

Cotton fibre are very strong

Good heat insulator

Breathable

Allow sweat to evaporate

Flexible

Cotton is renewable

Cotton plants while growing remove carbon dioxide from atmosphere

Question 8

Function of parenchyma

Answer 8

Suitable for Food storage and photosynthesis

Question 9

Function of collenchyma

Answer 9

Provide tensile strength

Mechanical support

Photosynthesis

Question 10

Function sclenchyma

Answer 10

Mechanical strength

Question 11

Middle lamella

Answer 11

First layer forms after cell division

Forms after cell division

Made of pectin , calcium pectate

Question 12

Primary cell wall

Answer 12

Build up against middle lamella

Made up of cellulose microfibrils pectin and a matrix of hemicellulose and other short chain carbohydrates which act as a glue

Flexible as cellulose microfibrils oriented in similar direction (parallel )

Question 13

Secondary cell wall

Answer 13

Develop as plant ages

Cellulose microfibrils laid densely at different angles to each other gives cell wall strength

More rigid + hemicellulose harden it further

Some are lignified ie wood