Teachers' Notes

Hydroponics Workshop

KS4 Programme of Study

Sc2 Life processes and living things

Green plants as organisms
3) Pupils should be taught:

Nutrition
a) the reactants in, and products of, photosynthesis
b) that the rate of photosynthesis may be limited by light intensity, carbon dioxide concentration or temperature
c) how the products of photosynthesis are utilised by the plant
d) the importance to healthy plant growth of the uptake and utilisation of mineral salts.

Answers to questions

Tomato plant growth rate at different nutrient levels

1. Name 5 minerals which you would expect to find in the nutrient solution, and find out what they are sued for in the plant, and what would happen if the plant lacked each mineral. Draw a three-column table to set out your answer.
   

   Mineral	Function in plant	Deficiency causes
   Nitrogen (or Nitrate)	Make proteins and genetic material.	Poor growth. Leaves may go yellow, or even fall off.
   Iron	Needed to make chlorophyll.	Leaves go yellow and may fail to grow fully.
   Magnesium	Found in chlorophyll.	Leaves go yellow.
   Phosphorus (or phosphate)	Important chemical for respiration & photosynthesis and needed for making genetic material.	Poor root growth, and young leaves could go purple.
   Potassium	Needed to make some chemical reactions proceed.	Yellow leaves, covered in small 'dead spots'

2. What seems to be the effect on overall plant growth if too many minerals are added at the start of growth
   
   Adding too many minerals early in plant growth prevents maximum growth. The slow start to growth may affect how well the plant grows in its later stages of development.
3. Why else must growers be careful not to add to many minerals to their plants as they grow?
   
   Other problems caused by too many minerals include environmental pollution (as excess minerals are washed away by rain. This is a problem mainly for out-door, soil-grown crops). Also, excessive minerals may cause plants have problems absorbing water. Absorption is caused by osmosis, which requires a more dilute solution outside the roots than inside. In extreme cases, water could actually be lostby the root to the surroundings.