<P> The main role of potassium is to provide the ionic environment for metabolic processes in the cytosol, and as such functions as a regulator of various processes including growth regulation . Plants require potassium ions (K) for protein synthesis and for the opening and closing of stomata, which is regulated by proton pumps to make surrounding guard cells either turgid or flaccid . A deficiency of potassium ions can impair a plant's ability to maintain these processes . Potassium also functions in other physiological processes such as photosynthesis, protein synthesis, activation of some enzymes, phloem solute transport of photoassimilates into source organs, and maintenance of cation: anion balance in the cytosol and vacuole . </P> <P> Typical symptoms of potassium deficiency in plants include brown scorching and curling of leaf tips as well as chlorosis (yellowing) between leaf veins . Purple spots may also appear on the leaf undersides . Plant growth, root development, and seed and fruit development are usually reduced in potassium - deficient plants . Often, potassium deficiency symptoms first appear on older (lower) leaves because potassium is a mobile nutrient, meaning that a plant can allocate potassium to younger leaves when it is K deficient . Deficient plants may be more prone to frost damage and disease, and their symptoms can often be confused with wind scorch or drought . The deficiency is most common in several important fruit and vegetable crops; notably potatoes, brassicas, tomatoes, apples, currants, gooseberries, and raspberries . Sugar beets, cereals, and clover are also commonly affected . Specific symptoms for each of these plants are as follows: </P> <P> In potatoes, tuber size is much reduced and crop yield is low . The leaves of the plant appear dull and are often blue - green in color with intervenal chlorosis . Leaves will also develop small, dark brown spots on the undersides and a bronzed appearance on the upper surfaces . </P> <P> In brassicas, leaves are blue - green in color and may have a low degree of intervenal chlorosis . Scorching along the outside edges of leaves is common, and leaves are often tough in texture due to slow growth . </P>

Deficiency symptoms of n p k in plants