Manganese toxicity may be a major constraint to cotton production in the states of São Paulo and Paraná and Mn deficiency may be a problem in the cerrado areas of Brazil. The objective of this experiment was to study the differential response of three cotton cultivars to Mn in nutrient solution. Cotton plants of the cultivars Coodetec 401, CNPA-ITM 90 and IAC 22 were grown in pots with nutrient solutions containing 0.0, 36.4, 72.8, 145.5 and 290.9 mmol L-1 of Mn for 70 days after emergence. Deficiency symptoms were noticed only in the Mn-free treatment in all of the three cultivars. There was an effect of Mn deficiency in the nutrient solution decreasing plant height, dry matter production, Mn accumulation and the retention of reproductive structures. There was no visual symptoms of Mn toxicity in any of the cotton cultivars, despite the high levels of Mn in the leaves. There was no difference in Mn accumulation among the three cotton cultivars, but IAC 22 was more sensitive to Mn toxicity and Coodetec 401 and CNPA-ITM 90 were more sensitive to Mn deficiency.Both Mn deficiency and toxicity may lead to decreased cotton production with no visual symptoms.
Gossipium hirsutum; micronutrient; mineral nutrition