Metal-induced oxidative stress in contaminated soils affects plant growth.
In the present study, we evaluated the role of seed endophyte FXZ2 on
Dysphania ambrosioides Zn/Cd tolerance and accumulation. A series of pot
experiments were conducted under variable Zn (500, 1,000, and 1,500 mg
kg 1) and Cd (5, 15, 30, and 60 mg kg 1). The results demonstrated
that FXZ2-inoculation significantly enhanced the growth of D. ambrosioides
and improved its chlorophyll and GSH content. In the rhizosphere, FXZ2
inoculation changed the chemical speciation of Zn/Cd and thus affected their
uptake and accumulation in host plants. The exchangeable and carbonatebound
fractions (F1 + F2) of Zn decreased in the rhizosphere of FXZ2-
inoculated plants (E+) as compared to non-inoculated plants (E-) under
Zn stress (500 and 1,000 mg kg 1), correspondingly, Zn in the shoots of
E+ decreased (p < 0.05). However, at Cd stress (30 and 60 mg kg 1), the
F1 + F2 fractions of Cd in E+ rhizospheric soils increased; subsequently, Cd
in the shoots of E+ increased (p < 0.05). FXZ2 could exogenously secrete
phytohormones IAA, GA, and JA. The study suggests that seed endophyte
FXZ2 can increase Zn/Cd tolerance of host plant by altering Zn/Cd speciation
in rhizospheric soils, as well as exogenous production of phytohormones
to promote growth, lowering oxidative damage while enhancing antioxidant
properties. For Zn/Cd accumulation, it has opposite effects: Zn uptake in
E+ plants was significantly (p < 0.05) decreased, while Cd accumulation in
E+ plants was significantly (p < 0.05) increased. Thus, FXZ2 has excellent
application prospects in Cd phytoextraction and decreasing Zn toxicity in
agriculturally important crops.