importance-of-water-and-inorganic-ions-to-plants

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

Water

• 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

Magnesium ions

• Important requirement for the production of chlorophyll

• This provides the green colour of stems and leaves and is essential for photosynthesis

Nitrate ions

• 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

Calcium ions

• These form important cell wall components

• Plants require calcium ions for proper growth

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

Apparatus

• Nutrient broths

• Test tubes

• Seedlings

• Aluminium foil

• Mass balance

Method

• 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

Variation of the practical

• 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