Azo dye-mediated regulation of total phenolics and peroxidase activity in thyme (Thymus vulgaris L.) and rosemary (Rosmarinus officinalis L.) clonal lines
Zx. Zheng et K. Shetty, Azo dye-mediated regulation of total phenolics and peroxidase activity in thyme (Thymus vulgaris L.) and rosemary (Rosmarinus officinalis L.) clonal lines, J AGR FOOD, 48(3), 2000, pp. 932-937
Thyme (Thymus vulgaris L.) and rosemary (Rosmarinus officinalis L.) clonal
lines, which were previously isolated from a heterogeneous seed population
by plant tissue culture techniques, have been targeted as potential plants
for phytoremediation of organic pollutants such as azo dyes and related aro
matic compounds. Three thyme clonal lines and three rosemary clonal lines w
ere tested for the ability to grow on hormone-free medium containing 0.01%
of azo dye Poly S-119. The results showed that dye tolerance was associated
with reduced phenolics and enhanced peroxidase activity in these clonal li
nes. There was a clear inverse correlation between total phenolics and pero
xidase activity in these plants in response to Poly S-119. The tolerance of
these clonal lines showed variations at different growing stages. These ob
servations suggested that the peroxidase activity was inducible. Because pe
roxidases are involved in lignification, wound healing, aromatic compound d
egradation, pathogen defense, and stiffening, the results suggest that azo
dye stimulated the defense response of thyme and rosemary clonal plants by
increasing the peroxidase activity. Stereomicroscopic observations revealed
that the azo dye was sequestered within the growing axis of the plant root
s, which may also enhance the polymerization of azo dye onto the cell wall
with the help of enhanced peroxidase activity.