Importance of Water & Inorganic Ions to Plants

Plant cells perform a variety of different functions
In order to perform these functions efficiently, the plant requires water and inorganic ions (minerals)
They are absorbed through the root hairs on the root and travel up the stem in xylem vessels
A plant will show certain symptoms (e.g. yellow leaves, stunted growth) when there is a deficiency in any one of these substances

Important component required for photosynthesis
Provides a transport medium for minerals
Maintains turgidity in plant cells though pressure in cell vacuoles
Regulates temperature - to ensure that enzymes can function at their optimum rate

Important requirement for the production of chlorophyll
This provides the green colour of stems and leaves and is essential for photosynthesis

Without nitrate ions, the plant would be unable to synthesise DNA, proteins and chlorophyll
- Enzymes are important proteins for which nitrate ions are needed
These molecules are essential for plant growth, as well as the production of fruit and seeds

Mineral deficiencies in plants Diagram showing the importance of magnesium and nitrate ions for plants

Practical: Investigating Plant Mineral Deficiencies

The following experiment could be done with any one of the mineral ions mentioned earlier
For this example, the focus will be on investigating the effect of a calcium deficiency on plants

Prepare three nutrient broths containing every mineral that a plant requires, but with different concentrations of calcium ions in each (high, medium and low)
- Label three test tubes for each of the nutrient broths (three 'high', three 'medium' and three 'low' = nine in total)
Take nine seedlings, ensuring that they are from the same plant and are the same age, and record the mass of each
Place one seedling on top of each test tube, suspending the roots in the nutrient broth
Cover the test tubes with aluminium foil to keep light away from the broth
Place the test tubes near a source of light and leave them for a few days
Remove each plant from the broth and carefully blot it dry before measuring the mass again
Record the end mass and use that to calculate the mean change in mass of the plants for each of the different nutrient broths
Make a note of any physical differences between the plants of the different groups

Another variation of the experiment mentioned above, is to investigate the effect on plant growth when the mineral is completely lacking
In this experiment you would have broths that contains all of the minerals, except the one that is being investigated
There would also need to be two control broths
- One would contain all the minerals
- The other would contain no minerals