Critical concentration: the concentration below which the growth is retarded Morophological changes due to deficiency- deficiency symptoms. Deficiency symptom first appear in older parts in case of actively mobilised elements – nitrogen, potassium And in young tissues in case of relatively immobile- sulpher, calcium
Premature leaf fall. Stunted growth, inhibition of cell division
Concentration that reduces dry wight by 10% is toxic.
Absorption has two phases First into the outer space- apoplast pathway Second into the inner space- symplast pathway
Translocation takes place through transpirational pull
Majority nutrients get through weathering and breakdown of rocks. Soil harbours nitrogen fixing bacteria, other microbes, holds water, supplies air to roots.
Only certain prokaryotes are capable of fixing nitrogen- called biological nitrogen fixation Nitrogenase enzyme helps fixation Azotobacter, Beijernickia, Rhodospirillum, Bacillus are microbes fixing nitrogen Anabaena and Nostoc- cyanobacteria