Plant Minerals

Plants require a smorgasbord of minerals to stay perky. Without absorbing things like magnesium, calcium and nitrate ions from the soil, plants will quickly start to wilt and discolour. On this page you’ll learn the importance of each mineral and how to investigate plant mineral deficiencies in the lab.

Plant Minerals

Like humans, plants need certain mineral ions to stay healthy. These mineral ions are found in the soil and are absorbed by the plant through their roots. A lack of any one of these ions will result in a mineral ion deficiency and will result in the plant appearing discoloured, wilted and generally a bit under the weather.

Calcium ions - calcium is a component of plant cell walls (specifically, it is needed to form calcium pectate which is found in the middle lamella). A lack of calcium means that the plant won’t grow properly and will display stunted growth with dead, curling leaves.

Nitrate ions - nitrogen is needed for two very important biological molecules - amino acids and nucleotides. A lack of nitrate ions means that less DNA and protein is synthesised. This will affect a range of processes in the plant including:

• Photosynthesis - translation of proteins such as chlorophyll and photosynthetic enzymes (e.g. Rubisco) will be reduced so less photosynthesis will take place. Leaves will turn yellow due to reduced chlorophyll production. The lack of glucose synthesised will result in reduced respiration, resulting in stunted growth.

• Cell division - since cell division relies on DNA replication, nitrate deficiency will reduce cell division and growth. This will contribute to stunted growth and will also result in reduced seed and fruit production.

Magnesium ions - magnesium is required for chlorophyll production. This means that magnesium deficiency will result in less photosynthesis taking place, which means less glucose is available for respiration. Less ATP is produced, which is needed for cellular processes such as cell division. The plant will show stunted growth and yellowing leaves.

Water - water is needed for a number of processes. It is a component of the cytoplasm, where chemical reactions take place, and of the vacuole which keeps the cell turgid. It is also required for photosynthesis, hydrolysis reactions and to regulate temperature as the evaporation of water from leaves helps to cool the plant down.

Investigating Plant Mineral Deficiencies

You can investigate the effect of different concentrations of mineral ions on plant growth in the lab by carrying out the following experiment:

• Prepare a nutrient broth and add the same volume to three test tube. Add varying concentrations of mineral ions to each of the three test tubes.

• Record the mass of three plant seedlings - these should all be of the same plant species and the same age. Place plant seedlings on top of each test tube so that their roots are suspended in the broth. You may need to support the seedling with some cotton wool to prevent it from falling into the test tube.

• Cover the test tube in foil - this will prevent light from reaching the broth and facilitating the growth of other organisms such as algae.

• Place the test tubes near a light source and leave to grow for a certain period of time (i.e. 1 week). Ensure the amount of light intensity each plant receives is the same. Other control variables include temperature and humidity.

• Record the new mass of each plant and calculate the change in mass over the one week period.

• Repeat the experiment at least three times and calculate the mean change in mass of the plants for each nutrient broth.

• The seedling which shows the largest change in mass will be the one that was placed in a nutrient broth with the optimum concentration of mineral ions.

Next Page: Photosynthesis