ABSTRACT
Frog egg-like bodies (FELBs), novel somatic embryogenesis (SE) structures first observed in Solanum nigrum, were induced in Rorippa indica. NaCl-mediated salt and mannitol-mimicked drought stresses induced FELBs in R. indica, which is very different from the induction by plant growth regulators (PGRs) under low light condition that was used in S. nigrum FELB induction. It demonstrated that NaCl or mannitol supplements alone could induce FELBs in R. indica, but with low induction rates, while the synergy of NaCl and mannitol significantly increased the FELB induction rates. For the combination of 5.0 g/L mannitol and 10.0 g/L NaCl the highest FELB induction rate (100%) was achieved. It suggests that the synergy of drought and salt stresses can replace PGRs to induce FELBs in R. indica. On medium supplemented with 1.0 mg/L gibberellic acid all the inoculated in vitro FELBs developed into multiple plantlets. Morphological and histological analyses confirmed the identity of FELBs induced in R. indica and revealed that FELBs originate from root cortex cells.
Subject(s)
Droughts , Plant Somatic Embryogenesis Techniques/methods , Regeneration/drug effects , Rorippa/physiology , Sodium Chloride/pharmacology , Stress, Physiological/drug effects , 2,4-Dichlorophenoxyacetic Acid/pharmacology , Animals , Anura , Frozen Sections , Indoleacetic Acids/pharmacology , Light , Mannitol/pharmacology , Ovum , Plant Roots/drug effects , Plant Roots/physiology , Plant Roots/radiation effects , Regeneration/radiation effects , Rorippa/drug effects , Rorippa/radiation effects , Stress, Physiological/radiation effectsABSTRACT
Hoagland solution was used to determine the root morphology properties of Rorippa globosa (Turcz.) Thell. and Rorippa palustris (Leyss.) Bess. Under the conditions of Cd spiked at 2.5 and 5 mg kg(-1), R. globosa showed all hyperaccumulative characteristics and was a Cd-hyperaccumulator. In contrast, R. palustris was a non-hyperaccumulator. The total root lengths, total root surface areas and total root volumes of R. globosa were not significantly decreased (p<0.05) compared to the control when 2.5 and 5 mg kg(-1) of Cd added. However, these 3 indexes of R. palustris were all significantly decreased (p<0.05) when 2.5, 5, 10, 20 and 40 mg kg(-1) Cd added compared its control. The average root diameters of R. palustris and R. globosa were not affected by Cd. These results showed that root morphology might be a factor of plant with strong tolerance to Cd.
Subject(s)
Adaptation, Physiological , Cadmium/metabolism , Plant Roots/anatomy & histology , Plant Roots/physiology , Rorippa/anatomy & histology , Rorippa/physiology , Adaptation, Physiological/drug effects , Biomass , Cadmium/toxicity , Organ Size/drug effects , Plant Roots/drug effects , Plant Shoots/drug effects , Plant Shoots/growth & development , Rorippa/drug effectsABSTRACT
Rorippa globosa has been identified as a new Cd-hyperaccumulating plant species. In the present study, growth responses of Rorippa globosa and its accumulation characteristics of Cd and As were examined under the condition of Cd-As combined pollution. The results showed that Cd and As had an antagonistic effect on enhancing the growth of the plants and Cd uptake and accumulation under the low concentration Cd and As treatments. When Cd and As concentrations were 10 mg/kg and 50 mg/kg, the highest height of the plants and the dry weight of shoots were up to 35.9 cm and 2.2 g/pot, respectively; and the accumulation of Cd in the leaves under the combined pollution was higher than that at the same level under single Cd pollution. However, there were synergic adverse effects on plant growth and Cd uptake under the high concentration Cd and As combined pollution. Meanwhile the accumulation of As in the roots was higher than that in the shoots, the translocation factor < or = 0.3 and the bioaccumulation factor < or = 0.6, which showed that Rorippa globosa had an excluding effect on As uptake. These results confirmed that Rorippa globosa had the strong tolerance ability to the Cd-As combined pollution, and the potential applied to phytoremediation of contaminated soil by Cd and As.
Subject(s)
Arsenic/metabolism , Cadmium/metabolism , Rorippa/growth & development , Rorippa/metabolism , Soil Pollutants/metabolism , Arsenic/toxicity , Biodegradation, Environmental , Cadmium/toxicity , Rorippa/drug effects , Soil Pollutants/toxicityABSTRACT
With the implementation of the new EU environmental framework directives, high tier risk assessments of chemicals will be increasingly needed. For high production chemicals, additional tests will complement the standard battery for aquatic toxicity assessments (daphnids, algae, and fish). In the context of a new chemical notification at the European Union level, we have developed a seed germination and root elongation toxicity test with the freshwater aquatic plant Rorippa nasturtium-aquaticum (water cress) to confirm the low environmental risk of the chelant [S,S]-EDDS. A 14 day semi-static growth inhibition test was conducted with daily renewal of the test solution. No concentration related inhibition was found on the basis of any of the criteria investigated, i.e., time and extent of germination, biomass, number of leaves, stalk and root lengths. The no-observed effect concentration was considered to be >or=387 mg SS-EDDS/l. Although germination was selected as an appropriate endpoint to assess the effect of a chelant on an aquatic plant (other endpoints would have been dependant on essential metals that are chelated in standard culture tests), the absence of dose related effects requires further tests with higher exposure concentrations and/or other toxicant(s) to assess the validity of the test as a general tool for aquatic risk assessment.
