L2 PLANT TISSUES AND ORGANS

Dermal Tissue - Epidermis

Single layer of cells forming outer covering and provides protection

Vascular Tissue - Xylem

• Thick-walled, hollow, dead cells

• Transports water and dissolved minerals

• Provides strength and structure

Vascular Tissue - Phloem

• Thin walled, hollow, living cells

• Transports sugar / nutrients

Ground Tissue - Cortex

• Large, thin-walled cells in roots/stems

• Stores starch (carbohydrates)

• Some perform photosynthesis

Ground Tissue - Mesophyll

• Large, thin-walled cells in leaves

• Perform photosynthesis

Meristem

Tiny, unspecialized cells at root/shoot tips, keep dividing to produce other tissues

Cambium

Single layer of tiny cells between xylem and phloem, keeps dividing to produce more xylem and phloem, causes secondary growth

What are the 2 main function of leaves?

1. Photosynthesis - traps light energy to produce sugar

2. Exchange of gases - O₂ and CO₂

How are leafs adapted for photosynthesis?

• Wide = more surface area to capture light

• Thin = easy gas movement

• Cuticle = reduces water loss

Identify A:

Cuticle

Identify B:

Upper Epidermis

Identify C:

Palisade Mesophyll

Identify D:

Spongy Mesophyll

Identify E:

Vascular Bundle

Identify F:

Guard Cells

Identify G:

Stoma (pl. stomata)

Compare palisade and spongy mesophyll cells.

• Palisade: Box-shaped, tightly packed, many chloroplasts → main site of photosynthesis

• Spongy: Irregular shaped, air spaces, some chloroplasts → gas exchange, some photosynthesis

What do stomata and guard cells do?

• Stomata: Small openings for gas exchange

• Guard cells open/close the stomata (open in light, close at night)

What is the main function of stems?

To support leaves and reproductive structures (flowers, cones)

What are the 2 types of stems and their characteristics?

• Herbaceous - soft, flexible, performs photosynthesis

• Woody - firm, rigid, no photosynthesis

Name and describe three examples of stems.

• Tuber (e.g. potato): Enlarged underground stem

• Bulb (e.g. onion): Compressed stem with fleshy leaves

• Stolon/Runner (e.g. strawberry): Horizontal stem above ground

What is the function of bark?

Provides protection from insects, herbivores, and environmental threats

What are the three main functions of roots?

1. Absorb water and minerals

2. Anchor the plant

3. Store carbohydrates

Name the three types of roots and their functions.

• Taproot: Strong anchor, absorbs water, stores food

• Fibrous: Spread out, absorbs water well

• Modified: Stores food & water

What is the role of the root cap?

Protective covering on the growing tip of the root

What is the role/function of root hairs?

Fragile parts of cells that grow from the main root that significantly increase the surface area for absorption