• Photosynthesis produces carbohydrates
  • Carbohydrates contain the chemical elements carbon, hydrogen and oxygen, which can be obtained from carbon dioxide and water

   

• However, plants contain many?other?types of?biological molecules, such as?proteins,?phospholipids,?nucleic acids?(DNA and RNA) and?ATP
• These molecules contain?other?chemical elements, for example:
  • Nitrogen?is required to make the?amino acids?that form?proteins, which are needed for cell?growth
  • Phosphorus?is required to make?phospholipids?for cell membranes,?nucleic acids?and?ATP
  • Magnesium?is required to make?chlorophyll
  • Calcium?is required to make calcium pectate for the?middle lamella?(the layer that provides?support?to plants by holding the?cell walls?of two plant cells together) and is important for?membrane permeability

   

• Plants obtain these elements in the form of?mineral ions?(e.g.?nitrate?ions or?phosphate?ions) that they actively?absorbed?from the soil through?root hair cells
• ‘Mineral’ is a term used to describe any?naturally occurring inorganic substance
• Without a source of these minerals, plants cannot?grow?or?function?properly
• The effect of these minerals on plant growth can be investigated by growing plants under?controlled conditions?and selectively?removing?each of these minerals in turn so the plants cannot access them

Apparatus

• Bryophyllum?plantlets
  • This plant reproduces?asexually?via budding, producing?genetically?identical?'daughter' plantlets
  • This removes the possibility that genetic differences are affecting plant growth

   

• Nutrient solutions:
  • Solution with?all mineral ions?(nitrate ions, phosphate ions, magnesium ions and calcium ions)?present?(this acts as a?control?to show that it is the lack of individual mineral ions that is affecting plant growth)
  • Solution with all mineral ions present except?nitrate?ions
  • Solution with all mineral ions present except?phosphate?ions
  • Solution with all mineral ions present except?magnesium?ions
  • Solution with all mineral ions present except?calcium?ions

   

• Measuring cylinder
  • To measure out equal volumes of nutrient solutions

   

• Test tubes
• Test tube rack
• Aluminium foil

Method

• Fill the tests tube with a?set volume?(e.g. 10 cm3) of each of the?nutrient solutions
• Cover the top of each test tube with foil and create a small hole in the foil
• For each test tube, take a?Bryophyllum?plantlet and push the?roots?of the plantlet through the hole in the foil, ensuring that the roots are?submerged?in the nutrient solution
• Place the test tubes in the?same location?and ensure that light intensity and temperature are kept at the?appropriate levels?to ensure normal plant growth
  • This is to ensure that these?abiotic factors?are?controlled?and kept the same for each of the plantlets

   

• After a set period of time (e.g. 2 weeks) observe the plantlets and take?qualitative?and?quantitative?measures of their?growth
  • Qualitative measures could include the?colour?of the plantlets and their?leaves, or how?wilted?the plantlet has become
  • Quantitative measures could include the?height?or?mass?of the plantlets or the length and width of their leaves

   

Results

• The table below outlines some of the common?effects?on?plant growth?when there is a?deficiency?of each of the four minerals

An example of the possible effects of mineral deficiencies on plant growth