Biology Revision Notes

#48 Plant's mineral requirements and fertilisers

Plants need minerals for healthy growth. Plant is in need for mineral ions to control chemical activities, grow, and produce materials. The most important minerals are Magnesium ions and Nitrates.

 1.Importance of nitrate and magnesium ions ( a. Nitrates

  • plants absorb nitrate ions from the soil, through their root hairs
  • nitrate ions combine with glucose -----> amino acids
  • amino acids bond together -----> protein
  • deficiency causes poor growth, especially of leaves. The stem becomes weak, lower leaves become yellow and die, while upper leaves turn pale green

Nitrates deficiency: Growth severely restricted, few stems;
yellowing of older foliage.


  • plants absorb magnesium ions from the soil solution
  • used for the manufacture of chlorophyll
  • each chlorophyll contains one magnesium atom
  • deficiency makes leaves turn yellow from the bottom of the stem upwards and eventually stops photosynthesis.

Mgnesium deficiency in potato plant.
(Growth fairly normal; foliage slightly pale; older leaflets develop central necrosis, turn yellow or brown


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