Plant Nutrition

Question 1

What is the function and adaptations of xylem vessel

Answer 1

Xylem Function: transport tissue for water and dissolved mineral ions
Adaptations:
Cells joined end to end with no cross walls to form a long continuous tube
Cells are essentially dead, without cell contents, to allow free passage of water
Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant

Question 2

Define Phloem Vessels

Answer 2

Phloem vessels – transport food materials (mainly sucrose and amino acids) made by the plant from photosynthesising leaves to non-photosynthesising regions in the roots and stem (pronounced: flow-em)

Question 3

Explain the adaptations of Root Hair Cell

Answer 3

Root hairs are single-celled extensions of epidermis cells in the root
They grow between soil particles and absorb water and minerals from the soil
Water enters the root hair cells by osmosis
This happens because soil water has a higher water potential than the cytoplasm of the root hair cell
The root hair increases the surface area of the cells significantly
This large surface area is important as it increases the rate of the absorption of water by osmosis and mineral ions by active transport

Question 4

Define Transpiration

Answer 4

Transpiration is defined as the loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata

Question 5

What are the functions of Transpiration

Answer 5

transporting mineral ions
providing water to keep cells turgid in order to support the structure of the plant
providing water to leaf cells for photosynthesis
keeping the leaves cool (the conversion of water (liquid) into water vapour (gas) as it leaves the cells and enters the airspace requires heat energy. The using up of heat to convert water into water vapour helps to cool the plant down)

Question 6

Where does Evaporation takes place

Answer 6

Evaporation takes place from the surfaces of spongy mesophyll cells
The many interconnecting air spaces between these cells and the stomata create a large surface area
This means evaporation can happen rapidly when stomata are open

Question 7

Explain Transpiration Stream

Answer 7

Water molecules are attracted to each other by cohesion - creating a continuous column of water up the plant
Water moves through the xylem vessels in a continuous transpiration stream from roots to leaves via the stem
Transpiration produces a tension or ‘pull’ on the water in the xylem vessels by the leaves
As water molecules are held together by cohesive forces (each individual molecule ‘pulls’ on the one below it), so water is pulled up through the plant
If the rate of transpiration from the leaves increases, water molecules are pulled up the xylem vessels quicker

Question 8

Explain the function and Adaptation of phloem vessel

Answer 8

The soluble products of photosynthesis are sugars (mainly sucrose) and amino acids
These are transported around the plant in the phloem tubes which are made of living cells (as opposed to xylem vessels which are made of dead cells)
The cells are joined end to end and contain holes in the end cell walls (called sieve plates) which allow easy flow of substances from one cell to the next

Question 9

Define Translocation

Answer 9

The transport of sucrose and amino acids in the phloem, from regions of production to regions of storage or use, is called translocation

Question 10

Define Source and Sink

Answer 10

“source” refers to the part of a plant (usually leaves) that produces substances like sugars through processes like photosynthesis
Sink” refers to the part of the plant that consumes or stores these substances, such as growing tissues, fruits, or storage organs like roots.