Plants

Carbon dioxide + water -------> glucose + oxygen

Chlorophil absorbs energy from light - can absorb most colours except green so plant can photosyntheise in most daylight conditions

Sunlight is absorbed chlorophil - this provides energy which is used for respiration, growth and reproduction

Experiments to prove chlorophil is needed for phtosynthesis:

Take a variagated leaf, and test with iodine - starch is only found where the plant is green - starch is found where photosynthesis takes place - therfore shows that photosynthesis only takes place where chlorophil is found

Leaves are adapted in many ways:

• Large surface area: bugger surface to absorb light
• Green: contains chlorophyll needed for photosynthesis
• Thin: gasses diffuse across the leaf faster
• Pores: for gas exchange
• Air spaces: lets the gasses through
• Veins: carry water needed for photosynthesis

The part of the leaf are also adapted:

• Waxy cuticle: waterproof to stop water loss
• Palisade cells: close to the light and are tightly packed, all full of chloroplasts
• Spongy layer: cells not tightly packed so there are air spaces to allow gasses in and out
• Guard cells: open and close to control gas exchange

Substances within the plant need to be transported around the plant

There are two separate transport systems:

Phloem:

• Thin walls of living tissues
• Transports sugar made in photosynthesis around the plant to growing or storage reasons

Xylem:

• Thick, strong non-living cells
• Transports water and minerals

Photosynthesis is effected by many factors, and if any one of these are in short supply, they become a limiting factor

Temperature: as photosynthesis involves enzymes, plants cannot photosynthesise at very low or very high temperatures

Light intensity: increasing the light intensity will increase the rate of photosynthesis, up to a point

Carbon dioxide: Even if there is sufficient light, the CO2 concentration need to be high in order for the plants to photosynthesise

The glucose made in photosynthesis is used in:

Respiration: Used immediately for respiration to provide energy to convert the rest of the glucose

Starch: stored in the insoluble form of starch (no osmotic effect unlike glucose), ready for when photosynthesis is not happening

Cellulose: to make plant walls, especially in fast growing plants

Nitrates: Combined with nitrates from the soil to make amino acids which then made proteins needed for growth

Lipids: for storage in seeds

DNA: used when the plant reproduces or repairs

Plants get the minerals they need to grow from the soil:

• Nitrates: make proteins for growth, deficiency = stunded growth
• Magnesium: make chlorophil for photosynthesis, deficency= yellow leaves

Artifical minerals come from fertilisers and are used to replace the minerals the plants take away from the soil

• Organic: help the soil structure, releases mineralls slowly (eg - manure)
• Chemical: correct balance of minerals but can harm wildlife when they wash off the soil (eg - amonia nitrates)

Hydropinics: plants are grown without soil, in water with aditional minerals. This increases the growth rate and is helpful in places with bad soil

Crop rotation: different  crops are planted each year so onle minerals won't be compleatly depleated