9.1 Leaves

IB Assessment Statement

Draw and Label diagrams to show distribution of tissues in the stem and leaf of a dicotyledonous plant

Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues.

9.1 Leaves

Leaves are involved in photosynthesis Leaves vary great in form but generally the

consist of a flattened portion called the blade and a stalk called the petiole that attaches to the blade to the stem.

9.1.1 Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant

Cuticle is a waxy layer which reduces water loss through the upper epidermis.

Upper epidermis is a flattened layer of cell that forms the surface of the leaf and makes the cuticle.

9.1.1 Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant

Palisade Layer: This is the main photosynthetic region of the leaf.

Vascular bundle: contains the transport system and vascular meristem tissue (x-xylem, p-phloem).

9.1.1 Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant

Spongy mesophyll: contains spaces that allows the movement of gases and water through the leaf tissue..

Lower epidermis: bottom surface layer of tissues which contains the guard cells that form each stoma.

9.1.3 Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues.( 3)

Leaf Tissues: (a) Phloem transports the

products of photosynthesis (sugars, amino acids).

(b) Xylem transports water and minerals into the leaf tissue from the stem and roots.

c) Epidermis produces a waxy cuticle for the conservation of water.

9.1.3 Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues.( 3)

(d) Palisade layer which is the main photosynthetic region.

(e) Spongy layer creates the spaces and surfaces for the movement of water and gases.

(f) Lower epidermis contains the stomatal pores which allow gas exchange with the leaf.

9.1.3 Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues.( 3)

The xylem and phloem tissues combine in the vascular tissue to provide support to the leaf.

Stomata a pore on the lower side of a leave that allows for gas exchange

Leaf Structure

9.1.1 Assessment Statement

9.1.1 Draw and label plan diagrams to show the distribution of tissues in the stem and leaf of a dicotyledonous plant. Either sunflower, bean or another dicotyledonous plant with similar tissue distribution should be used. Note that plan diagrams show distribution of

tissues (for example, xylem, phloem) and do not show individual cells. They are sometimes called “low- power” diagrams.

9.1.1 Assessment Statement

9.1.3 Explain the relationship between the distribution of tissues in the leaf and the functions of these tissues. This should be restricted to dicotyledonous plants. The functions should include: absorption of light,

gas exchange, support, water conservation, and the transport of water and products of photosynthesis.