Anatomical Changes in Prosopis tamarugo Phil. Seedlings Growing at Different Levels of NaCl Salinity

Seedlings of Prosopis tamarugo were grown in artificial substrateswith additions, of 200, 400 and 600 mM NaCl, and without salttreatment. Salinity induced anatomical changes in the roots,stems and leaflets. The diameters of the roots of seedlingsgrown in the increasing salt concentrations (up to 400 mM) wereprogressively smaller and differentiation of the stelar tissueswas delayed. At an NaCl concentration of 600 mM, the root structurewas strongly altered. On the contrary, stem diameter increasedas salinity rose. In the stems of seedlings grown in a concentrationof 200 mM NaCl, secondary xylem differentiation appeared earlierthan in the controls. At a concentration of 400 mM NaCl, disorganizationof the vascular cylinder of the stem was evident. Leaflets ofseedlings grown in 200 mM NaCl showed a delay in structuraldifferentiation: no water-storage cells or ‘special cells’could be seen. The leaflets from plants grown in 400 mM NaCl,had larger numbers of intercellular air spaces; probably anindication of the beginning of tissue disorganization. A progressivedecrease in cell size of leaflets as salinity rose was alsodemonstrated. Prosopis tamarugo Phil., seedling, salinity, anatomical changes