Potassium in plants

It is known as a luxuriant nutrient as plants uptake it in huge quantities.

Functions of potassium in plants

• Potassium helps form mechanical tissues in cereals, encouraging strong stem and root systems resulting in resistance to lodging.
• It is essential to convert carbon dioxide and hydrogen into sugars and translocate sugars and starch formation. Therefore, the element is vital for tuber development in tuber crops and is essential for grain formation in cereals and sugar accumulation and translocation in sugarcane.
• It helps maintain cellular organization by regulating the permeability of cellular membranes and keeping the protoplasm in a proper degree of hydration by stabilizing the emulsions of colloidal particles. This helps in the maintenance of osmotic potential and water uptake.
• It serves as an enzyme activator or cofactor for some 46 enzymes. Its salts stabilize various enzyme systems. It plays a catalytic role in activating several enzymes to incorporate amino acids in proteins, synthesis of peptide bonds, etc. The presence of potassium is essential for optimal activation of aldehyde dehydrogenase, phosphate acetyl-transferase, etc.
• The element is essential for protein synthesis. It plays a vital role in photosynthesis by directly increasing growth and leaf area index and stomatal opening.
• It increases resistance in plants against drought, heat frost, and various diseases caused by fungi nematodes and other micro-organisms.
• In fruit crops, it improves color, flavor and increases the size and weight of the fruits. 
• It enhances the quality of crops like tobacco.
• It counteracts the damaging effects of excess nitrogen.
• It increases crop resistance to certain diseases.

Deficiency symptom of potassium in plants 

• Generally, a plant deficient in potassium is stunted in growth with a pronounced shortening of the internodes and has a busy appearance.
• The external symptoms of potassium deficiency are easily recognized on the leaves of the plant. A -mottled chlorosis first occurs, followed by the development of necrotic areas at the tip and margin of the leaf. The continued deficiency develops chlorosis between the veins and coloration along with the leaf tips and the margins. The coloration may vary from light grey to bronze, reddish-brown or dark brown depending upon the species of the affected plants. The potato and certain Brassica spp. bear crumpled and raised lamina. 
• Acute deficiency results in pale and chlorotic interveinal spaces, whereas leaf tips and margins are scorched and necrotic. Because of the mobility of potassium, these symptoms generally appear first on the more mature leaves. Also, in many cases, there is a tendency for the leaf tip to curve downward, and, as in the case of the French bean and potato, marginal regions may roll inward toward the upper surface.
• Potassium deficiency in tomato plants causes disintegration of pith cells and increases the differentiation of secondary phloem parenchyma into sieve tubes and companion cells.
• In root crops like sugar-beet, sweet potato, the roots become slender, poorly developed.
• The deficiency is aggravated more under cold and wet weather. The deficiency reduces the resistance of plants against bacterial and fungal infections. The drought and frost tolerance of plants is also found to be reduced.
• Translocation of photosynthates and nutrient uptake is adversely affected.

Toxicity of oversupply of potassium in plants

• Crops/plants’ maturity is delayed.