Caracterização de sintomas de deficiência de boro em cebola (Allium cepa L.) em estado de produção

Abstract

Onion plants (Allium cepa L. ‘Baia Periforme Precoce’) were cultivated in sand irrigated with a modified Johnson's nutrient solution. After 109 days, the nitrogen of the solution was reduced to 1/4 of the normal concentration and the phosphorus, sulfur, calcium and magnesium concentrations were reduced to half. At the same time, boron was eliminated from the solution used to irrigate half of the plants. The leaves of the plants submitted to the boron deficient solution became thick, brittle and presented a blue-green color. Eventually, the leaves presented necrosis beginning at the tip which caused the death of a large number of them. A mottled appearance was also identified. In the boron-deficient bulbs, the scales became hard and rough-surfaced, with necrosis in the internal scales. In histological observations, the epidermal cells were cubic and without cuticle; the nuclei of the parenchymatous cells were swollen and the vascular bundles necrotic. After 54 days of storage, 70% of the boron-deficient bulbs presented rotten, and the others lost more fresh weight than the normal bulbs during the storing period.