Plants of Zea mays were grown for 12 days in sulfur-deficient medium according to a standard technique applied specifically for formation of aerenchyma cavities in the adventitious roots. At the level of meristem and root elongation zone, cortical microtubules involved in formation of trophic-type lysigenous aerenchyma were examined. For the first time, organization of tubulin microtubules in cells lining the cavities of aerenchyma was investigated. In addition, we determined the stages of programmed cell death in which microtubules are destroyed, and also compared those with published data on programmed cell death due to deprivation of sulfur, phosphorus, potassium, nitrogen, and oxygen in the nutrient medium. Cortical and endoplasmic microtubules, which constitute the main components of the plant cytoskeleton, were studied. Comparison of stepwise destruction of cortical and endoplasmic microtubules with the stages of programmed cell death revealed that endoplasmic microtubules undergo disorganization later in time than cortical ones. It is suggested that disorganization of cortical microtubules occurs at the first stages of the programmed cell death process and results in destruction of rigid cell wall, which, in turn, contributes to disruption of cytoplasmic membrane. The latter causes invaginations of the cytoplasmic membrane, which is considered to be a hallmark of early stages of cell death. It is noted that intact organization of endoplasmic microtubules persists until the final stages of cell destruction and elimination.
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