Plants

Wax cuticle

Protective layer on top of the leaf that prevents water from evaporating

Upper epidermis

Thin and transparent layer that allows light to enter the palisade mesophyll layer underneath

Palisade mesophyll

Column-shaped cells tightly packed with chloroplasts to absorb more light and maximise photosynthesis

Spongy mesophyll

Contains internal air spaces that increase surface area to volume ratio for diffusion of gases (mainly carbon dioxide)

Lower epidermis

Contains guard cells and stomata

Guard cell

Absorbs and loses water to open and close the stomata, allowing carbon dioxide in and oxygen out

Stomata

Where gas exchange takes place; opens during the day and closes at night; water also evaporates from here; mostly found on the underside to reduce water loss

Vascular bundle

Contains xylem and phloem to transport substances to and from the leaf

Xylem

Transports water into the leaf for photosynthesis and transpiration

Phloem

Transports sucrose and amino acids around the plant

Large surface area (leaf)

Increases surface area for diffusion of carbon dioxide and absorption of light for photosynthesis

Thin

Allows carbon dioxide to diffuse quickly to palisade mesophyll cells

Chlorophyll

Absorbs light energy so that photosynthesis can take place

Network of veins

Allows transport of water to the cells of the leaf and carbohydrates from the leaf

Stomata (adaptation)

Allows carbon dioxide to diffuse into the leaf and oxygen to diffuse out

Epidermis is thin and transparent

Allows more light to reach the palisade cells

Thin cuticle made of wax

Protects the leaf without blocking sunlight

Palisade cell layer at top of leaf

Maximises absorption of light as it hits chloroplasts directly

Spongy layer

Air spaces allow carbon dioxide to diffuse through the leaf, increasing surface area

Vascular bundles

Thick cell walls in the tissue help support the leaf and stem

What is photosynthesis?

the process by which plants manufacture carbohydrates from raw materials using energy from light

What are the raw materials required for photosynthesis?

Carbon dioxide and water

What is the function of chlorophyll?

Absorbs light energy and transfers energy from light into energy from chemicals for the synthesis of carbohydrates

How can the carbohydrates produced by plants during photosynthesis be used?

Converted into starch molecules that act as an effective energy source, converted into cellulose to build cell walls, glucose can used in respiration, converted to sucrose for transport, and convert into lipids for energy source in seeds and amino acids

What is magnesium needed for?

To make chlorophyll

what are nitrates needed for?

Source of nitrogen needed to make amino acids (to build proteins)

What does a magnesium deficiency cause?

Yellowing between the veins of leaves (chlorosis)

What does a nitrate deficiency cause

Sounded growth and yellowing of leaves

How do plants obtain nitrates and magnesium?

Absorbed from the soil by root hair cells in active transport

How to test a leaf for the presence of starch?

Boil to kill cells and break down cell walls and membranes, place in hot ethanol to remove chlorophyll so the color change can be seen, rinse leaf in water to soften, do iodine test.

How do you investigate the need for chlorophyll?

Use a variegated leaf compare starch test results from green and white areas, iodine test will have white areas show negative result, with green areas showing positive result as it has starch showing that chlorophyll is needed for photosynthesis to occur

How do you investigate the need for light?

Place a plant in dark cupboard for 24 hrs before investigation ensuring the leaves contain no starch. Cover part of the leaf with aluminum foil and place in sunlight, exposed parts will photosynthesis and store starch. Perform iodine test, exposed parts turn blue black, covered part stays orange-brown

How do you investigate the need for carbon dioxide

Destarch two plants to ensure the leaves contain no starch, place each plant in a bell jar covering the pots with plastic to prevent carbon dioxide from escaping. In one plant place soda lime at the entrance to absorb carbon dioxide and a beaker of sodium hydroxide to absorb any carbon dioxide in the air. The other plant will have water in the bell jar, allow them to absorb light, and do iodine test.

What is the balanced chemical equation for photosynthesis

6CO2 + 6H20 (arrow) C6 H12 O6 + 6 O2

What are the limiting factors of photosynthesis?

Temperature, light intensity, and carbon dioxide concentration

Define a limiting factor

something present in the environment in such short supply that it restricts life processes

Why is water not considered a limiting factor

the amount needed is relatively small compared to the amount of water transpired from a plant so there is hardly ever a situation where there is not enough water for photosynthesis

Relationship between carbon dioxide and photosynthesis

More carbon dioxide is present the greater the rate of photosynthesis until some other factor limits

Relationship between light intensity and photosynthesis

The more light a plant receives the faster the rate of photosynthesis

How does temperature affect the rate of photosynthesis

As temperature increases the rate of photosynthesis increases as the reaction is controlled by enzymes