RESUMO
Two species of perennial Phyllanthus (Euphorbiaceae) (Phyllanthus orbicularis and Phyllanthus discolor, both endemic to ultramafic areas of Cuba, and their natural hybrid, Phyllanthus xpallidus) were selected for metal localization microanalysis. Different plant tissues were analyzed by X-ray fluorescence, inductively coupled plasma-atomic emission spectroscopy, and scanning electron microscopy coupled with an energy-dispersive X-ray probe. All of the studied taxa are nickel (Ni) hyperaccumulators and significant concentrations of this element were found in different leaf and stem tissues. The highest Ni content was found in the laticifer tubes, whereas leaf epidermis Ni content resulted to be much more relevant in terms of total metal storage. Calcium and magnesium were found more evenly distributed in leaf and stem tissues.
Assuntos
Euphorbiaceae/metabolismo , Níquel/metabolismo , Solo , Álcalis , Cuba , Euphorbiaceae/ultraestrutura , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de VarreduraRESUMO
The root ultrastructure of seedlings grown in anaerobic conditions was investigated in four neotropical species: Sesbania virgata, Erythrina speciosa, Sebastiania commersoniana (all present in waterlogged or flooded areas), and Schizolobium parahyba (that occupies mainly dry areas). Anaerobiosis induced an increase in the size of mitochondria, dilatation of cristae and of the endoplasmic reticulum, and fragmentation or concentric arrangement of reticulum saccules. The ultrastructural alterations were reversible only for S. virgata and E. speciosa. The seedlings of S. parahyba and S. commersoniana were more sensitive to oxygen deprivation and presented extensive cell disruption. The results are discussed in terms of energy supply.