ABSTRACT
Introduction:
Chemically modified biochars are a new generation of biochars that have a great
ability to absorb and stabilize
environmental pollutants. In this
research, the physiological performance of
mint plants (
Mentha crispa L.) under
fluoride and
cadmium toxicities and biochar
treatments was evaluated.
Methods:
Four levels of
soil toxicities including non-toxic, 600 mg NaF kg-1
soil, 60 mg Cd kg-1
soil, and 600 mg NaF kg-1
soil + 60 mg Cd kg-1
soil were applied. The biochar addition to the
soil was 25 g kg-1 (non-biochar, solid biochar, H2O2, KOH, and H3PO4-modified biochars).
Results:
The results showed that the application of biochar and especially chemically modified biochars reduced
fluoride (about 15-37%) and
cadmium (30-52%) contents in
mint leaves, while increased
soil pH and
cation exchange capacity (CEC),
nitrogen (12-35%),
phosphorus (16-59%),
potassium (17-52%),
calcium (19-47%),
magnesium (28-77%),
iron (37-114%),
zinc (45-226%), photosynthetic pigments of leaves and
plant biomass (about 10-25%) under toxic conditions.
Discussion:
The biochar-related
treatments reduced the
osmotic stress and osmolytes content (
proline, soluble
proteins, and
carbohydrates) in
plant leaves.
Plant leaf water content was increased by solid and modified biochar, up to 8% in toxic conditions. Furthermore, these
treatments reduced the
production of stress
hormones [
abscisic acid (27-55%),
salicylic acid (31-50%), and jasmonic
acid (6-12%)], but increased indole-3-
acetic acid (14-31%) in
plants under
fluoride and
cadmium stresses. Chemically modified biochars reduced
fluoride and
cadmium contents of
plant leaves by about 20% and 22%, respectively, compared to solid biochar.
Conclusion:
This result clearly shows the superiority of modified biochars in protecting
plants from
soil pollutants.
