Edexcel IGCSE Biology Section 2e - Plant Nutrition

Photosynthesis

A process where plants use carbon dioxide and water, in the presence of chlorophyll and light, to make glucose and oxygen.

Chlorophyll

Green pigment found in leaves that absorbs the light energy needed for photosynthesis.

Leaf epidermis

Outer layer of cells in the upper and lower regions of a leaf.

Cuticle

Thin waxy layer that covers the leaves of plants. It reduces water loss by evaporation.

Stomata

Pores found in the lower epidermis of a leaf that allow carbon dioxide to diffuse in and oxygen and water vapour to diffuse out.

Guard cells

Highly specialised cells that can alter their shape to open or close the stomata in a leaf.

Palisade mesophyll cells

Elongated photosynthetic cells, found in the middle layers of a leaf, containing hundreds of chloroplasts.

Spongy mesophyll cells

Rounded, loosely packed cells, with air spaces between them. They are found below the palisade cells.

Xylem

Vessels that carry water and disolved minerals.

Phloem

Vessels that transport sugars made in photosynthesis around the plant.

Starch

Carbohydrate made by plants, found only in the green parts of leaves.

Sucrose

A disaccharide (double sugar unit) that is the main sugar carried in phloem.

Cellulose

A polysaccharide that is the main constituent of plant cell walls.

Soda lime

A substance that absorbs carbon dioxide from the air - often used in experiments.

Iodine solution

Used to test for starch. Changes colour from yellow-brown to blue-black if starch is present.

Hydrogencarbonate Indicator Solution

A substance that can be used to show the presence of carbon dioxide. In air it is orange but in high carbon dioxide concentrations it turns yellow, and in low concentrations it turns purple.

Elodea

An aquatic plant often used to measure the rate of photosynthesis by counting the number of oxygen bubbles formed per minute.

Limiting factor

The component of a reaction that is in 'shortest supply' so that it prevents the rate of the reaction increasing, in other words sets a 'limit' to it.

Nitrate deficiency

Plants have stunted growth and older leaves turn yellow because these ions are required to make amino acids, proteins, chlorophyll and DNA.

Magnesium deficiency

Plant leaves turn yellow because these ions are needed to form part of a chlorophyll molecule.