4.2.2 - Plant Stems

Question 1

Describe The Structure Of Xylem Vessels
(5 Points)

Answer 1

~ Cells walls contain lignin, enabling the vessel to withstand pressure created by the movement of water.

~ Form long, hollow straw-like structures that are formed by dead cells.

~ Do not contain any cytoplasm or organelles, that could slow down the flow of water.

~ Have no end walls between the cells.

~ Water and mineral ions move into and out of the vessels, through pits in the walls that do not contain lignin.

Question 2

Describe The Function Of Xylem Vessels
(2 Points)

Answer 2

~ Vascular tissue that transports dissolved minerals and water around the plant.

~ Provide structural support.

Question 3

Describe The Structure Of Sclerenchyma Fibres
(4 Points)

Answer 3

~ Consist of bundles of dead cells.

~ Form long, hollow tubes and have end walls present.

~ Cell walls are thickened with lignin, but do not contain pits.

~ Have more cellulose in their walls, compared to other plant cells.

Question 4

Describe The Function Of Sclerenchyma Fibres
(2 Points)

Answer 4

~ Not involved in the transport of substances.

~ Provide structural support.

Question 5

Describe The Structure Of Phloem Fibres
(3 Points)

Answer 5

~ Formed from cells arranged in tubes.

~ Made of many various cell types, its bulk are made up of sieve tube elements and companion cells.

~ Other cell types of phloem tissue include parenchyma for storage and strengthening fibres.

Question 6

Describe The Function Of Phloem Fibres
(4 Points)

Answer 6

~ Transport organic compounds, particularly sucrose.

~ This transport can occur up and down the plant, known as translocation.

~ Organic compounds are dissolved in water to form sap.

~ Has no support function in a plant.

Question 7

Describe The Structure & Function Of The Phloem Sieve Tube Elements
(4 Points)

Answer 7

~ Are living cells and are joined end to end to form sieve tubes.

~ Sieve plates with sieve pores -> allows for the continuous movement of the organic compounds.

~ Cellulose cell wall -> strengthens the wall to withstand the pressure moving the organic compounds.

~ No nucleus or other organelles -> maximises the space for the translocation of organic compounds.

~ Thin cytoplasm -> reduces friction yo facilitate the movement of organic compounds.

Question 8

Describe The Structure & Function Of The Phloem Companion Cells Elements
(5 Points)

Answer 8

~ Linked with a sieve tube elements, carry out the living functions for both themselves and their sieve tubes.

~ Has nucleus and other organelles present -> providing metabolic support to sieve tube elements.

~ Transports proteins -> moves organic compounds in and out the sieve tube elements.

~ Large numbers of mitochondria -> Provides ATP for active transport.

~ Plasmodesmata -> Link to sieve tube elements allowing organic compounds to move form companion cell to sieve tube elements.