Transport in plants

Question 1

Phloem

Answer 1

• Phloem cells carry food substances such as sugars up and down stems to growing and storage tissues. This transports of food substances is called translocation.
• Phloem cells are living and are arranged in columns.

Question 2

Xylem

Answer 2

• Xylem cells carry water and minerals from the roots to the leaves and are therefore involved in transpiration.
• The xylem cells are called vessels. They are dead cells, and the lack of living living cyptoplasm leaves a hollow lumen. Their cellulose walls have extra thickening of lignin, giving gret strength and support.

Question 3

What is the vascular bundles made of?

Answer 3

• Xylem and phloem cells form vascular bundles in dicotyledonous plants.
• Xylem and phloem are made up of specialised plant cells. Both types of tissues are continuous from the root, through the stem and into leaf.

Question 4

What is transpiration?

Answer 4

Transpiration is the evaporation and diffusion of water from inside leaves. This loss of water from leaves helps to create a continuous flow of water from the roots to the leaves in xylem.

Question 5

What does transpiration ensure?

Answer 5

Transpiration ensures that plants have water for cooling by evaporation, photosynthesis and support from cells’ turgor pressure, and for transport of minerals.

Question 6

The rate of transpiration can be increased by:

Answer 6

• An increase in light intensity, which results in stomata open.
• An increase in temperature, causing an increase in the evaporation of water.
• An increase in air movement, blowing away air containing a lot of evaporated water.
• A decrease in humidity, allowing more water to evaporate.

Question 7

Root hairs

Answer 7

Root hairs are projections from root hair cells. That produce a large surface area for water uptake by osmosis.

Question 8

Where are stomatal openings?

Answer 8

Most of them are on the shaded lower surface.

Question 9

How are plant cells adapted efficient photosynthesis?

Answer 9

Plant leaves are adapted for efficient photosynthesis by having stomata for entry and exit of gases. The spongy mesophyll cells are also covered with a film of water in which the gases can dissolve. This water can therefore readily escape through the stomata.

Question 10

How are leaves adapted to reduce water loss?

Answer 10

• By having a waxy cuticle covering the epidermal cells.
• Its guard cells are able to change the size of the stomatal openings. The guard cells contain chloroplasts, so photosynthesis in the presence of water and light) will produce sugars, increasing turgor pressure, causing the cells to swell. Due to differential thickness of their walls, the guard cells curve, opening the stomata.
• Further reduction in water loss is brought about by having few stomata, small stomata, the position of stomata mainly in the lower epidermis and their distribution