Plant organs: Leaf

Question 1

Functions of leaves

Answer 1

Trap light, allow for gaseous exchange, stomata and guard cells controls water loss

Question 2

Describe the external leaf structure

Answer 2

Flattened blade is the lamina which is connected to the stem by a petiole. The lamina has an apex (end of leaf), base (where the petiole attaches), margin (edge of leaf), mid-rib (veins of leaf)

Upper side of leaf called the dorsal side (bright, shiny), other is ventral side (dull, no shine). Leaves without a petiole are called sessile leaves. Veins can either run in a net/parallel venation

Question 3

Internal leaf structure: Main groups of tissues

Answer 3

1. Epidermal tissues
2. Mesophyll tissues
3. Conducting tissues in veins

Question 4

2 types of mesophyll tissues

Answer 4

1. Palisade mesophyll
   - Elongated and attached to the upper epidermis
   - Lots of chloroplasts, closely packed
2. Spongy mesophyll
   - Attached to lower epidermis
   - Fewer chloroplasts, spread out

Question 5

2 types of conducting tissues

Answer 5

1. Xylem
   - Dead cells, long cylindrical cells, have tracheids
   - Transport water and salts from roots and give strength and support
2. Phloem
   - Sieve tubes are long cylindrical tubes
   - Companion cells lie next to sieve tubes and they have a nucleus
   - Phloem transports manufactured food down to the roots
   - Companion cells control the activities of sieve tubes