<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> <P> In tomatoes, the stems are woody and growth is slow . Leaves are blue - green in color, and the intervenal area often fades to a pale gray color . Leaves may also have a bronzed appearance and yellow and orange patches may develop on some of the leaflets . Fruits often ripen unevenly and sometimes have green patches near the stalks . </P> <P> In apples, leaves are scorched around the edges, and intervenal chlorosis is common . Apple fruits often have a slightly acidic or woody taste . </P>

Where do potassium ions come from in plants