CHAPTER 8: TRANSPORT IN PLANTS

What are the function of xylem?

Transport of water and mineral ions

Explain the transport of water in xylem;

Water enters the leaves from the leaves and moves upwards through the stem

Explain the transport of mineral ions:

Dissolved mineral ions are transported from roots to the rest of the plant

What are the features of xylem vessels?

Made of dead cells / one - way transport/ long hollow tubes / no nuclei and cytoplasm / thick cell wall made of lignin / no cross walls / pits, small pores without lignin in some cells

Why the cells of xylem vessels are dead?

If they were alive, they would absorb and use the water and mineral ions

Why the tubes of xylem vessels are long and hollow?

Forms continuous pipelines for water leaves

Why the xylem vessels don't have nuclei and cytoplasm?

Less resistance, more space for water movement

What is the function of lignin?

Waterproofs the vessel, adds flexibility and support, prevents collapse under pressure

Why the xylem vessels don't have cross walls?

Allows free, upward flow of water

What is the function of pits?

Allows sideways water movement to nearby tissues

What is the function of phloem?

Transport of sucrose and amino acids

Explain the transport of sucrose in phloem?

Produced in leaves by photosynthesis then transported to growing regions and storage organs

Explain the transport of amino acids:

Essential for protein synthesis in growing parts

What is the direction of movement in phloem?

In both directions ( up and down)

What are the features of phloem cells?

Movement occurs in both directions / made of living cells / contains sieve tubes and companion cells

What is a sieve tube?

Transport sugars, no nucleus, simplified cells

What is a companion cell?

Support and regulate transport / have a nucleus / fully functional cells / provide energy for transport

What are the features of root hair cells?

• Located near the root tip

• long and thin hairlike extensions from the surface area of a root hair cell

• each cell has one fine projection

• nucleus andd cytoplasm are present

what are the functions of root hair cells?

• absorption of water

• absorption of mineral ions

• increased surface area

• anchoring the plant

What de the root hair cells do by anchoring the plant?

Helps rocks grip the soil firmly as they grow

What are the physical features of rood hair cells?

Long extension ( hair ) / thin cell wall / no cuticle / large vacuole / close to xylem

Explain the reason of long extensions

Increases surface area for absorption

E explain the reason for thin cell walls or root hair cells?

Allows easy movement of water and minerals

Explain the reason for no cuticle in root hair cells?

Maximizes water uptake from the soil

Explain the reason for large vacuole in root hair cells?

Stores water and mineral ions

Explain why root hair cells are close to xylem?

Allows quick transport

What is transpiration?

Water vapor is lost from the aerial parts of a plant. Through stomata

Now transpiration happens?

→ water is absorbed from the soil by root hairs.

→ it travels upwards through the xylems in the stem

→ water reaches the mesophyll cells in the leaf where it evaporates

‘→ the water vapor diffuses out through open stoma

Why transpiration is important?

→ cooling the plant ( evaporation)

→ water movement

→Transport of minerals

• →

• Maintains turgidity

Factors affecting transpiration rate

• light intensity: increases

• temperature: warmer air increases evaporation and diffusion

• humidity: decreases as humidity increases

• wind: speeds up evaporation

• stomatal opening: wider stomata increases diffusion

Now water vapor leaves the cell in transpiration?

• evaporation from mesophyll cells

• build up of water vapor

• diffusion through the stomata

• loss of water vapor

importance: a continuous stream of vapor

cools the leaf

What is wilting?

When a plants leaves and stems droop or collapse due to lack of water

→Transpiration causes water loss from the leaves

Factors that can lead fo wilting

• hot weather: evaporation and transpiration rate increases

• dry or windy conditions: accelerates water loss

• low soil moisture

• damaged roots

• blocked xylem vessels

What is translocation?

The movement of sucrose and amino acids in phloem from sources to sinks

What is source?

Where substances are produced, amino acids and sucrose, young leaves

What is sink?

Where substances are used or stored, roots and mature leaves

What are the features of translocation?

• Carries sucrose and amino acids

• upwards and downward

• sieve tube elements and companion cells

• active transport, ATP

• distribute nutrients to growing or storage parts