EFFECTS OF POTASSIUM DEFICIENCY ON SOME ORGANIC CONSTITUENTS IN PLANTS
Adequate potassium was needed to give maximum amounts of sugars and fructosan in the tops and stubble. In the grass grown without added K, increasing N-fertiliser increased the contents of ammonium-N, nitrate-N, free amino acids, glutamine, asparagine and amines (agmatine and putrescine) and decreased the protein-N content. When N-fertiliser was balanced with K-fertilizer-, all these soluble N-fractions decreased and protein-N increased. As glutamine and asparagine were predominant compounds most affected by potassium, estimating these two amides indicates the state of nitrogen metabolis in the plants. The amine content of plants provides a more sensitive indication of potassium deficiency than does the potassium content. Since the determination of agmatine is much easier than of putrescin agmatine content is proposed as an indicator of the potassium status of plants.