Endogenous salicylic acid is required for promoting cadmium tolerance of Arabidopsis by modulating glutathione metabolisms.

A few studies with NahG transgenic lines of Arabidopsis show that depletion of SA enhances cadmium (Cd) tolerance. However, it remains some uncertainties that the defence signaling may be a result of catechol accumulation in NahG transgenic lines but not SA deficiency. Here, we conducted a set of hydroponic assays with another SA-deficient mutant sid2 to examine the endogenous roles of SA in Cd tolerance, especially focusing on the glutathione (GSH) cycling. Our results showed that reduced SA resulted in negative effects on Cd tolerance, including decreased Fe uptake and chlorophyll concentration, aggravation of oxidative damage and growth inhibition. Cd exposure significantly increased SA concentration in wild-type leaves, but did not affect it in sid2 mutants. Depletion of SA did not disturb the Cd uptake in either roots or shoots. The reduced Cd tolerance in sid2 mutants is due to the lowered GSH status, which is associated with the decreased expression of serine acetyltransferase along with a decline in contents of non-protein thiols, phytochelatins, and the lowered transcription and activities of glutathione reductase1 (GR1) which reduced GSH regeneration. Finally, the possible mode of SA signaling through the GR/GSH pathway during Cd exposure is discussed.

Decline in extractable kitasamycin during the composting of kitasamycin manufacturing waste with dairy manure and sawdust.

The aim of this study was to propose a feasible treatment of kitasamycin manufacturing waste by examining extractable kitasamycin and evaluating its compost maturity during the composting of waste with different ratios of dairy manure and sawdust over a 40-day period (volume/volume/volume; M1, 0/80/20; M2, 10/70/20; and M3, 30/50/20). During composting, the concentration of extractable kitasamycin in kitasamycin-contaminated composts declined rapidly, and was undetectable in M2 within 15 days. M2 also achieved the highest fertility compost, which was characterised by the following final parameters: electrical conductivity, 2.34 dS cm(-1); pH, 8.15; total C/N, 22.2; water-soluble NH4(+), P, and K, 0.37, 3.43, and 1.05 g kg(-1), respectively; and plant germination index values, 92%. Furthermore, DGGE analysis showed a dramatic increase in the diversity of bacterial species during composting. In contrast, a high concentration (121 mg kg(-1)) of extractable kitasamycin still remained in the M3 compost, which exerted an inhibitory effect on the composting, resulting in reduced bacterial diversity, high values of electrical conductivity and water-soluble NH4(+), a low C/N ratio, and a low plant germination index value. Furthermore, 3.86 log (CFU g(-1)) kitasamycin-resistant bacteria were still present on day 40, indicating the biological degradation contributed to the decline of extractable kitasamycin.

Cadmium stabilization with nursery stocks through transplantation: a new approach to phytoremediation.

Disposal of heavy metal contaminated biomass after phytoremediation is still unfeasible. This paper presents a viable phyto-extraction approach in which metals in contaminated soils are stabilized by nursery stocks before transplantation for greening. In this respect, two pot-experiments are reported comparing seven nursery stocks species exposed to different Cd levels. The first experiment revealed that Cd was mainly stabilized in the roots of all species studied. Greater amounts of Cd were accumulated in the epidermis than cortex plus stele. Cupressus Blue Ice showed greatest tolerance to the 100 and 200 mg kg(-1) Cd stresses. The second experiment additionally evaluated the possible risk of Cd release after transplanting the Cd treated plants into uncontaminated soil. After 120 days of transplantation, the relatively trace amounts of Cd in the roots of Euonymus japonicus, Pittosporum tobira and C. Blue Ice had either been partially transferred into the shoots or released into the soil. The highest Cd concentration increase in bulk soil (0.428 mg kg(-1)), however, was much lower than the environmental quality standard for soils of China (1 mg kg(-1)). The potential effectiveness of this technique in the use of Cd-contaminated soil and further investigation needed in the field trials were also evaluated.