Chlorine (Cl) - Micronutrients
The role of Cl- in plant is not clearly understood. Cl- is required in Hill reaction, the water splitting reaction of photosystem II. In the presence of Cl- both the evolution of O2 and photophosphorylation are enhanced. Cl- may also influence photosynthesis indirectly via its effect on stomatal regulation of the guard cells. Wilting of leaves at the margin is a deficiency symptom of chloride. Cl- deficiency is noticed only rarely.
The presence of Cl- in the atmosphere and in the rain water is more than enough to meet the demand of the crops. In fact, its presence in excess in plants is a more serious problem. Crops growing on salt affected soils often show symptoms of Cl- toxicity. These are burning of leaf tips or margins, bronzing, premature yellowing and abscission of leaves.