7.1. Structure of Plant Transport Tissues

Question 1

Why do plants not need a transport system for gases?

Answer 1

• Plants energy needs are generally small compared with those of animals
• They can therefore rely on diffusion to supply their cells with oxygen and remove carbon dioxide
• Leaves are thin and have a large surface area inside them in contact with the air spaces
• This means that diffusion is sufficient to supply mesophyll cells with CO2 for photosynthesis and to remove oxygen

Question 2

Plants have how many transport systems

Answer 2

2: Xylem and Phloem

Question 3

Xylem

Answer 3

Transports water and inorganic ions from the roots to all other parts of the plant

Question 4

Phloem

Answer 4

Transports substances made in the plant such as sucrose and amino acids, to all parts of the plant

Question 5

Epidermis

Answer 5

• A continuous layer on the outside of the plant
• one cell thick
• function: protection
• in stems and leaves, covered with a waterproof waxy cuticle
• in leaves, pores called stomata are present in epidermal layer
• in roots, root hair cells are present

Question 6

Endodermis

Answer 6

• one cell thick

- surrounds vascular tissue in stems and roots

Question 7

Mesophyll

Answer 7

• found between the upper and lower epidermis in a leaf
• specialised for photosynthesis
• 2 types: palisade mesophyll and spongy mesophyll

Question 8

Cambium

Answer 8

• A layer of unspecialised cells in between the xylem and phloem tissue in stems and roots

Question 9

Cortex

Answer 9

The outermost layer inside the epidermis. It has the epidermis on one side and endodermis on the other. It is the tissue to the outside of the vascular bundle

Question 10

Pith

Answer 10

The tissue in the centre of the stem (inside the ring of vascular bundle
- only found in stems

Question 11

Features of Xylem

Answer 11

• Dead, empty cells with no end walls (xylem vessel elements) - easy continuous flow of water
• Long, hollow tubes through which water moves by mass flow around the plant
• Cell wall containing cellulose and lignin - makes wall impermeable and provides strength
• Narrow lumen increases adhesion of water to the walls and prevents breakage of water column
• Pits in cell walls allow movement of water out of the vessel element or to neighboring tissues

Question 12

Features of Phloem

Answer 12

Sieve tube element with:

• cell wall containing cellulose with many plasmosdesmata forming direct links between cytoplasm of sieve tube element & companion cell
• cytoplasm with some mitochondria and other organelles. NO NUCLEUS
• Sieve plates - a perforated end wall allowing mass flow of phloem sap through the sieve pores
• Companion cells - connected to sieve tube elements with cytoplasm containing numerous organelles, including a nucleus and many mitochondria