Silver white, very brittle heavy metal or element (Mn). In nature it often occurs in many minerals in combination with iron. These are brownite, manganese dioxide, hausmannite and manganite as well as iron ores. Manganese is important for the vine as a nutrient in small quantities. It is involved in carbohydrate and protein metabolism, as well as in the formation of cell membranes and also supports photosynthesis. Close interrelationships between manganese and iron are suspected in the metabolism of plants. On alkaline soils with a high pH value, a lack of plant-available manganese is most frequently to be expected. Likewise, high levels of calcium also inhibit absorption and transport in the plant.