Resumen

OLIVARES, Elizabeth; PENA, Eder  y  AGUIAR, Guillermina. NUTRICIÓN MINERAL Y ESTRÉS OXIDATIVO POR METALES EN ESPINACA Y LECHUGA, EN COMPARACIÓN CON DOS MALEZAS ASOCIADAS, EN CULTIVOS SEMI-URBANOS . INCI [online]. 2002, vol.27, n.9, pp.454-464. ISSN 0378-1844.

The concentration of metals and foliar organic compounds affected by the stress produced by them were evaluated. Phytotoxic concentrations of metals may produce senescence or induce a detoxification process. Soil composition was studied, and nutrients and acid phosphatase (PAA) and nitrate reductase (NRA) activities were evaluated in roots and leaves. Crop species such as lettuce (L), and spinach (S) were compared with their associated weeds Ageratum conyzoides (A) and A. houstonianum (H) in two cultivation sites located in towns near Caracas, San Antonio (Site 1) and San Pedro (Site 2). The soils in Site 2 were richer in K, Ca, P, Mg, Mn and Zn, showed lower concentrations of Ni, higher pH and percent of sand, than those in Site 1. The concentration of Al, Fe and Ca was very high in the weeds compared to the crop species, and Cr was high in H. The leaves of A showed the highest concentration of total phenols. The highest values of chlorophyll, carotenoids and lipid peroxidation were found in H. The highest concentration of K, Mg, Mn, Cu and Zn were found in S. The concentration of Ni, Co, Pb and Cd were low or undetectable in the four species from the two studied sites. Lettuce from a commercial hydroponic crop showed better nutrition than those from soils. It is concluded that the weeds showed higher concentrations of metals and compounds associated to the oxidative stress than the two crop species.

Palabras clave : Ageratum ; Aluminio ; Asteraceae ; Espinaca ; Lechuga ; Malezas ; Metales .