The effects of hyperalkaline, thermo-mineral water from Slatina on the morphology and anatomy of pea
plants (Pisum sativum L.), were examined after eleven days of treatment with a mixture of tap water and Slatina water
in 3:1 (T1) and 1:1 ratios (T2). Complete growth arrest of seedlings was observed in the Slatina water (T3). The alkalin-
ity of external media was recovered to pH 8 within four days only in T1 and T2. Analysis of morphological parameters
(the length of the main root, root application zone, number of lateral roots) indicated that the thermo-mineral water
either promoted (T1) or inhibited (T2) the formation of lateral roots and plant growth. Comparative histological and
anatomical analyses showed that inhibition of lateral roots was accompanied by an increase in the xylem and phloem.
These changes in root morphology were accompanied by an increase in the activity of superoxide dismutase (SOD: E.C.
1.15.1.1) and peroxidase (POD: E.C 1.1.1.17) in the soluble fraction, whereas the activities of ascorbate oxidase (AAO:
E.C. 1.10.3.3) bound to the cell wall and ionic POD decreased. The lower ratio of Slatina water in the hydroponic solu-
tion contributed to a more developed mesophyll with significantly higher AAO activity in the leaves and the induction
of ionic POD isoforms. Besides alkalinity and excess NaCl, we suggest that a specific combination of metals (e.g. Ca
and Mg) might be responsible for subtle changes in the cell area and xylem development, leading to dramatic changes
in root anatomy.