Lead accumulation, growth responses and biochemical changes of three plant species exposed to soil amended with different concentrations of lead nitrate.

Lead (Pb) contamination of soil is a serious environmental problem, adversely affecting ecosystems, globally. Phytoremediation is an alternative to conventional methods of soil remediation. The success of phytoremediation depends on the identification of suitable native plant species with high biomass to deal with metal contamination. In the present experiment, response of Eclipta prostrata (L.) L., Scoparia dulcis L. and Phyllanthus niruri L. to increase in concentrations of PbNO3·5H2O in the soil for a period of 30 days was tested to assess their suitability in phytoremediation. Pb accumulation in all the three plants was in a concentration-dependent manner. Although S. dulcis survived the soil metal concentrations, it exhibited a stunted growth; P. niruri was found susceptible to Pb toxicity; E. prostrata recorded a maximum uptake of 12484 µg/g dry weight in its root and 7229 µg/g dry weight in its shoot, without any adverse impact on growth traits. Bioconcentration factor and translocation factor of the three plants were also calculated, which revealed that E. prostrata has Pb accumulation potential. Therefore, enzymatic antioxidant activities and transmission electron microscopic analysis were carried out to determine the physiological adaptation and tolerance of E. prostrata to Pb stress. Overall, E. prostrata is identified as a tolerant plant showing Pb hyperaccumulation tendencies with essential features for phytoextraction.

Improving plant transformation using Agrobacterium tumefaciens.

Here, we report a quick and low-cost method to improve plant transformation using Agrobacterium tumefaciens. This method involves the use of physical wounding, ultrasound, and an increase in exposure time to the bacteria. We show how the transformation rate increased from 0 to 14% when an ultrasound pulse of 10 s was used in conjunction with 96 h of bacterial exposure in Eclipta alba explants.

Effect of allelopathic rice varieties combined with cultural management options on paddy field weeds.

BACKGROUND: A number of techniques, including cultural management, allelopathy and bioherbicide, have been considered as alternatives for synthetic herbicides, but successful weed control will require the careful integration of these multiple techniques. This study was conducted to assess the use of allelopathic rice varieties in combination with cultural management options on paddy weeds, in order to develop an allelopathy-based technique to reduce herbicide use in paddies. RESULTS: The weed-suppressive effects of the rice varieties tested varied highly with allelopathic trait, planting pattern and cultural management including planting density, flooding depth and duration and supply of nitrogen. Allelopathic rice varieties PI312777 and Huagan-1 demonstrated much stronger weed suppression than the non-allelopathic variety Huajianxian under the same planting pattern and cultural management. Their weed-suppressive effect was increased with cultural management options. In particular, if integrated cultural management options of allelopathic rice varieties included a low-dose (bensulfuron-methyl, 25 g AI ha(-1), a third of the recommended dose) herbicide application, the emergence and growth of most weeds found in paddy fields was completely controlled. No grain yield reduction for allelopathic varieties occurred under integrated cultural management options, whereas with the non-allelopathic variety a reduction of up to 45-60% was measurable even with the low-dose herbicide application. CONCLUSION: The allelopathic potential of rice varieties will likely have a great impact on paddy weed control if integrated with cultural management options and application of low doses of herbicides. Therefore, it is feasible to reduce herbicide input in paddies if allelopathic rice is grown under integrated cultural management practices.

[Interference of allelopathic rice Huakangcao 78 on weeds under different ecological conditions].

A pot culture experiment was conducted to examine the interference effectiveness of allelopathic rice Huakangcao 78 on weeds Echinochloa crusgalli L., Cyperus difformis L., and Eclipta prostrata L. as affected by rice leaf age during transplanting, plant density, and soil surface water depth and its retaining days. The results showed that Huakangcao 78 could significantly reduce the dry weight of weeds compared with non-allelopathic rice Lemont. The control effectiveness of Huakangcao 78 on E. crusgalli L. was better when the weed was at 0-1.5 leaf age than at 1.5-2.4 leaf age, and that on C. difformis L. was better when the weed was at 0-0.3 leaf age than at 0.8-2.0 leaf age. The interactive effectiveness between rice leaf age during transplanting and plant density on weed control was better than that between the leaf age and soil surface water depth and its retaining days. To increase the rice leaf age during transplanting and plant density could significantly promote the control effectiveness of Huakangcao 78 on weeds.