iron, a mineral element essential for healthy vine growth in small amounts. Normally enough iron is taken up from the soil to meet the plant’s needs, but iron deficiency in leaves is not uncommon. So-called lime-induced chlorosis is a well-known disorder of the vine when it is grown on alkaline or calcareous soils. Leaves turn yellow, particularly between the veins, because iron is unavailable for the manufacture of chlorophyll. In alkaline and calcareous soils, iron is in an insoluble form which makes it unavailable to the vine roots. Soils can be measured for their ability to provide sufficient iron to the vine (see soil alkalinity).