Germination, cytotoxicity, and mutagenicity in Lactuca sativa L. and Passiflora alata Curtis in response to sewage sludge application.

Abstract

The physical and chemical characteristics of the soil can influence plant growth. When sewage sludge (SS) is applied as a soil fertilizer, the accumulation of non-essential elements contained in it can be toxic for plants. The aim of this study was to understand the effect of SS dosage on the cell cycle of Lactuca sativa L. meristematic cells and on the initial growth of L. sativa and Passiflora alata Curtis. Nine concentrations of SS + distilled water (mg dm-3) corresponding to 0, 20, 40, 60, 80, 120, 160, 320, and 520 t ha-1 were tested in four replicates of 25 seeds. Chemical analysis showed an increase in pH of the sludge from 0 to 80 t ha-1 SS followed by its stabilization thereafter. The highest electrical conductivity was observed at 520 t ha-1 SS. SS negatively affected the germination and initial growth of seedlings from P. alata and L. sativa. Cytogenetic analysis on 6000 L. sativa meristematic cells for each treatment revealed that SS could adversely affect the genetic stability of this species. SS concentrations above 120 t ha-1 adversely affected the germination and early seedling growth of L. sativa and P. alata. At high concentrations (120 t ha-1), SS induced genetic lesions in L. sativa, along with chromosomal and nuclear alterations.