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Thickening or stunting of Opuntia ficus-indica cladodes is one of the most striking diseases of the crop. It is characterized by the development of abnormally thickened cladodes, dwarfism and malformations. To describe the histological changes and to quantify hormones and nutritional elements in thickened cladodes, microscopic histological sections were compared, and hormones and nutritional elements were quantified from thickened and healthy cladodes. Greater heterogeneity was found at the cellular and tissue level in symptomatic compared to asymptomatic cladodes. Hypertrophy and hyperplasia were found in some areas of the thickened cladode tissues. Moreover, an increase in tracheids and vessel elements was observed, and several of these vascular bundles were damaged. On the other hand, the presence of a greater amount of amyloplasts and calcium oxalate crystals was found in the parenchyma of thickened cladodes than in the healthy ones. Additionally, there were no significant differences in the accumulation of the ABA, IAA, AG3 and zeatin hormones between thickened and healthy cladodes from plants established in the greenhouse with experimental nutritional conditions. On the contrary, the potassium, nitrogen, sodium and zinc elements were accumulated with lower quantity in thickened than in healthy cladodes, with levels of 68.3%, 67.6%, 55.3% and 36.2%, respectively, while phosphorus, calcium, magnesium, manganese and iron were accumulated in greater amounts in thickened cladodes compared to healthy cladodes, with levels of 20.3%, 17.2%, 16.1%, 256.1% and 200.2%, respectively. These findings improved our understanding of the physiological and anatomical mechanisms of this disease. |
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