M2.2.1 - Plant Structure

Question 1

Vascular plants

Answer 1

Have a transport system composed of xylem and phloem to move substances around the plant

Question 2

Non-vascular plants

Answer 2

Do not have transport systems. Nutrients consequently absorbed by diffusion or osmosis

Question 3

Xylem structure

Answer 3

• Transports: water, water soluble nutrients (minerals)
• Direction: only upwards, from the root to the leaf, unidirectional
• Structure: long open chambers; no end walls → continuous open tubes
• Energy: Passive transport
• Position in vascular bundles: inner
• Outer cells: dead cells

Question 4

Phloem

Answer 4

• Transports: organic molecules (sugars, hormones, etc.)
• Direction: two way travel; bidirectional
• Structure: sieve plates - not continuous
• Energy: Active transport
• Position in vascular bundles: outer
• Outer cells: living cells, as they need energy for transport

Question 5

Root system (of flowering plants and conifers)

Purpose + outline how it achieves this

Answer 5

Purpose: anchor and support the plant, absorb water and mineral ions

Roots have a large surface area so more substances can diffuse in. To this end, it has root hairs. Water and nutrients are absorbed into the xylem.

Question 6

Parts of a root

Answer 6

• Root cap: pushes the root through the soil
• Area of cell division: cells divide very quickly, pushing the root cap
• Area of cell elongation: matured cells are elongated (roots growing longer)
• Area of maturation: cells have root hairs, increasing surface area

Root hairs: contain large vacuoles to absorb water and dissolved substances.

Taproot example: palm tree
Fibrous root example: grass

Question 7

Dermal tissue

Answer 7

• Covers the outer layers of roots, stems and leaves.
• Functions: transpiration, gas exchange and defence.

e.g. epidermis
Can contain: root hairs, waxy cuticle, stomata

Question 8

Vascular tissue

Answer 8

Xylem and phloem, occurring in vascular bundles.
Cambium are the cells between xylem and phloem

Question 9

Ground tissue

Answer 9

Tissue that isn’t dermal or vascular

Parenchymal
* Unspecialised, loosely packed, thin walled
* Photosynthesis, cellular respiration and storage (e.g. food storage of potatos)

Collenchymal
* Elongated thickened walls
* Support and wind resistance (strings through celery)

Sclerenchymal
* Very thick cells walls containing lignin
* For support and strength (tough fibres in jute)

Question 10

Leaf structure

Layers of a leaf

Answer 10

1. Waxy cuticle
2. Epidermis (upper and lower), reducing evaporation and preventing bacteria/fungi entering
3. Palisade mesophyll - tightly packed to maximise light absorption. Majority of chloroplast
4. Spongy mesophyll - loosely packed to allow for efficient diffusion of carbon dioxide and oxygen diffusion.
5. Stomata (majority in lower), changing depending on sunlight and water availability, allows gas exchange to occur