Function and Deficiency symptoms of Iron in plants
Function of Iron in plants
i. Iron forms cytochromes, heam and metalloproteins like ferredoxin and heamoglobin in plants. These cytochromes play a vital role in oxidative and photophosphorylations during respiratory electron transport and photosynthesis, respectively. The ferredoxin helps in reduction of carbon dioxide, sulphate and of atmospheric nitrogen.
ii. It synthesises chlorophyll precursor (protoporphyrin-9) which forms chlorophyll in green plants.
iii. Its specific requirement has been identified in synthesis of enzymes like oxido-reductase, sulphate oxidase, catalase, peroxidase and aconitase etc.
iv. Being a constituent part of metabolically active compounds, iron is responsible for all major metabolic processes in plants such as nucleic acid metabolism and RNA metabolism of chloroplasts.
Deficiency symptom of Iron in plants
i. The deficiency aggravates under high alkalinity, high concentration of calcium carbonate, bicarbonate, phosphate, heavy metals, water logging and low temperature.
ii. Young leaves of fruit trees become chlorotic. Generally, the younger leaves are most affected, the more mature leaves sometimes show no chlorosis at all. Primarily, this is because of the relative immobility of iron in the plant. Thus, the younger leaves cannot withdraw iron from the older leaves. One feature of iron-induced chlorosis is its characteristic interveinal nature, the surface of the leaf usually showing a fine reticulate network of green veins setting off chlorotic areas as the vascular tissues in the veins retain Fe for longer time. The chlorosis starts first at basal portions then spreads towards anterior leaf margins. Continued deficiency results in complete bleaching of leaves which may dry and become papery.
iii. In case of cereals leaves may wither and the apices may hang down. In sorghum, the tissues just below the necrotic leaf apex and along the anterior margins may secrete a viscous fluid.
iv. The mustard seedlings remain necrotic and they collapse.