In addition to carbon dioxide, warmth and water, plants need minerals, too. The table below shows the most important minerals, how they are used by plants and the consequences for the plant when the mineral is not available:
|nitrates||making amino acids, which are joined together to make proteins used for growth||poor growth, yellow leaves|
|phosphates||making cell membranes and DNA||poor root growth, discoloured leaves|
|potassium compounds||making enzymes for photosynthesis and respiration||poor fruit and flowers, discoloured leaves|
|magnesium compounds||making chlorophyll molecules to trap light for photosynthesis||yellow leaves|
Vocabulary used in farming
- pesticides, two types, see insecticides and fungicides below
- insecticides, used to kill insects
- fungicides, used to kill fungi
- herbicides, used to kill unwanted plants (weeds)
- greenhouses, used to grow plants in optimum conditions
- hydroponics, a system used to grow lettuce and tomato plants without water
- in organic farming no manufactured chemicals are used, but alternative methods, like biological control (other animals are used to feed on pests)
DDT was a very effective pesticide which has now been banned, as it built-up in food chains and killed many animals.
Break down of dead animals and plants into simpler chemicals is called decay. Microorganisms called decomposers (mainly bacteria and fungi) cause decay. Sewage and dead plants are broken down into compost.
The remains of dead plants and animals are called detritus. Detritivores depend on detritus for their food. Such animals are maggots, woodlice and earthworms. Detritivores are very important in food chains, as they recycle chemicals in the environment; for example, carbon dioxide and nitrogen.
We will now go through some questions on minerals, farming and decay.