Sylvie Renault

Effect of High Salinity Tailings Waters Produced From Gypsum Treatment of Oil Sands Tailings on Plants of the Boreal Forest

Bitumen extraction methods currently in use in the operating oil sands plants produce large volumes of fluid tailings. Ions leached from the ore and added by process chemicals during the extraction process result in tailings waters containing elevated ionic content relative to the non-process-affected waters of the area, in particular the sodium, sulfate, and chloride ions. It is anticipated that the areas requiring reclamation will be affected by this high salinity of the process waters. The objectives of this study were to test the impact of a tailings alternative (consolidated tailings process, based on gypsum treatment of extraction tailings) on the viability of plant species of the northern boreal forest and to determine the relative salt tolerance and suitability of selected plant species for land reclamation. Seedlings were grown for 4 weeks in a greenhouse in solution culture containing mineral nutrients and various dilutions of consolidated tailings water and with Na2SO4 additions (1 g L−1 and 3 g L−1). Of all examined plant species, raspberry and strawberry seedlings were the most susceptible to damage, while the seedlings of white spruce, black spruce and lodgepole pine survived, but showed some effects. In the willow and aspen seedlings, there was a rapid loss of leaves, which were quickly replaced by new, morphologically different leaves. Dogwood and hybrid poplar showed high tolerance to all treatments.

Effects of NaCl and Na2SO4 on red-osier dogwood (Cornus stolonifera Michx) seedlings

Sodium chloride and sodium sulfate are commonly present in extraction tailings waters produced as a result of surface mining and affect plants on reclaimed areas. Red-osier dogwood (Cornus stolonifera Michx) seedlings were demonstrated to be relatively resistant to these high salinity oil sands tailings waters. The objectives of this study were to compare the effects of Na2SO4 and NaCl, on growth, tissue ion content, water relations and gas exchange in red-osier dogwood (Cornus stolonifera Michx) seedlings. In the present study, red-osier dogwood seedlings were grown in aerated half-strength modified Hoaglands mineral solution containing 0, 25, 50 or 100 mM of NaCl or Na2SO4. After four weeks of treatment, plant dry weights decreased and the amount of Na+ in plant tissues increased with increasing salt concentration. Na+ tissue content was higher in plants treated with NaCl than Na2SO4 and it was greater in roots than shoots. However, Cl− concentration in the NaCl treated plants was higher in shoots than in roots. The decrease in stomatal conductance and photosynthetic rates observed in presence of salts is likely to contribute to the growth reduction. Our results suggest that red-osier dogwood is able to control the transport of Na+ from roots to shoots when external concentrations are 50 mM or less.

The effect of salinity on the emergence and seedling growth of Picea mariana, Picea glauca, and Pinus banksiana

Mining operations in areas of the boreal forest have caused salinity issues to be a major concern for reclamation. One of the factors determining successful reclamation is the ability of species to self-propagate. The effects of salinity on the seedling emergence and early growth of three boreal forest conifers: Picea mariana, Picea glauca, and Pinus banksiana were determined. Seeds were planted in sand moistened with solutions of various concentrations of sodium chloride or sodium sulfate. Seedling emergence was monitored on a daily basis and growth parameters assessed after 6 weeks. The emergence of Pinus banksiana seedlings was least affected by salinity, and at certain concentrations, emergence even appeared to be stimulated by the presence of salt. Picea glauca was the most sensitive of the species studied. Hypertrophia was observed in all species at high concentrations of Na2SO4, and an increase in salt levels caused a corresponding reduction in seedling height and weight, root length and number of lateral roots.

Biochemical and Biophysical Changes in Relation to Cold Hardiness

Winter temperatures below −40°C are not uncommon in northern regions. Low temperatures, often combined with strong winds, pose a significant survival challenge to perennial woody plants. Unlike deciduous species, most northern conifers retain their needles over winter. This allows the trees to photosynthesise during warm days in early spring and late fall and therefore take advantage of good conditions (Fischer and Holl 1991; Wang and Zwiazek 1999a). However, this strategy requires freezing resistance mechanisms to protect the needles in addition to the other living tissues.

Germination, growth and gas exchange of selected boreal forest seedlings in soil containing oil sands tailings

Greenhouse experiments were conducted to determine the effects of soil enriched in fine tailings (FT), produced by the oil sands extraction, on germination, seedling growth and physiology of several plant species of the boreal forest. The germination of seeds was initially delayed by 15% FT in dogwood (Cornus stolonifera Michx) and jack pine (Pinus banksiana Lamb) but not in white spruce [Picea glauca (Moench) Voss]. In the second set of experiments we showed that all dogwood seedlings survived 6 months of treatment with 15% FT while the survival rates of raspberry, jack pine and white spruce seedlings were reduced to 44, 55 and 94%, respectively. FT reduced root and shoot dry weights in raspberry seedlings and the number of lateral shoots in jack pine and white spruce seedlings. In raspberry and jack pine seedlings, reductions of gas exchange were recorded. The results of our study suggest that the modifications of soil chemistry, texture and structure by FT may all contribute to the observed phytotoxic effects.

Effects of consolidated tailings water on red-osier dogwood (Cornus stolonifera Michx) seedlings

As part of their tailings management, the oil sand industries plan on producing consolidated (composite) tailings (CT), in which an inorganic coagulant aid (gypsum) is added to create a non-segregating deposit. The water associated with this treatment contains potentially phytotoxic levels of sodium, sulfate, chloride, boron, aluminum, fluoride and strontium. Since CT water is expected to saturate deposits in the reclamation areas, it may affect successful reclamation of these sites. Red-osier dogwood (Cornus stolonifera Michx) was demonstrated to be relatively salt resistant and to have high potential for the reclamation of mining areas. In the present study, we used red-osier dogwood to examine the effects of CT water on the accumulation of ions within plant tissue, growth, gas exchange, water potentials and chlorophyll concentration. CT water reduced shoot lengths and dry weights in treated plants. The roots of treated plants accumulated higher concentrations of sodium and chloride than did shoots. The accumulation of sodium and chloride was accompanied by an increase in magnesium and calcium and a decrease in potassium in the roots, while the levels of potassium increased in the leaves. CT water altered gas exchange and water potentials in seedlings, and resulted in a decrease in chlorophylls a and b. The results suggest that the mechanisms of salt resistance in red-osier dogwood seedlings involve the restriction of sodium transport from roots to shoots.

Enhanced oxidative stress in the jasmonic acid-deficient tomato mutant def-1 exposed to NaCl stress

Jasmonic acid (JA) has been mostly studied in responses to biotic stresses, such as herbivore attack and pathogenic infection. More recently, the involvement of JA in abiotic stresses including salinity was highlighted; yet, its role in salt stress remained unclear. In the current study, we compared the physiological and biochemical responses of wild-type (WT) tomato (Solanum lycopersicum) cv Castlemart and its JA-deficient mutant defenseless-1 (def-1) under salt stress to investigate the role of JA. Plant growth, photosynthetic pigment content, ion accumulation, oxidative stress-related parameters, proline accumulation and total phenolic compounds, in addition to both enzymatic and non-enzymatic antioxidant activities, were measured in both genotypes after 14 days of 100 mM NaCl treatment. Although we observed in both genotypes similar growth pattern and sodium, calcium and potassium levels in leaves under salt stress, def-1 plants exhibited a more pronounced decrease of nitrogen content in both leaves and roots and a slightly higher level of sodium in roots compared to WT plants. In addition, def-1 plants exposed to salt stress showed reactive oxygen species (ROS)-associated injury phenotypes. These oxidative stress symptoms in def-1 were associated with lower activity of both enzymatic antioxidants and non-enzymatic antioxidants. Furthermore, the levels of the non-enzymatic ROS scavengers proline and total phenolic compounds increased in both genotypes exposed to salt stress, with a higher amount of proline in the WT plants. Overall the results of this study suggest that endogenous JA mainly enhanced tomato salt tolerance by maintaining ROS homeostasis.

Nitrogen Fixation Does Not Alter the Effects of Salinity on Soybean Resistance to a Generalist Caterpillar

Premise of research. Nitrogen deficiency, salinity, and herbivory are common stress factors faced by plants, but their simultaneous effects have been overlooked. The goal of our study was to test whether plant resistance to a generalist herbivore was altered by salt stress or symbiotic nitrogen fixation, or both. Methodology. We grew Bradyrhizobium-inoculated and noninoculated soybean plants under two salinity levels, subjected half of them to herbivory by cabbage looper larvae, and measured plant performance and resistance to herbivory. Pivotal results. Prior to herbivory, NaCl-treated plants had lower biomass, chlorophyll content, leaf trichome density, whole-plant fixed nitrogen, and biomass allocation to roots, while the levels of N, K, Ca, Mn, B, and Cl in shoot tissues were higher than in control plants. Most salt-stressed plants produced no seeds. Without salt stress, herbivory reduced plant growth by 25% and seed production by 13%. Constitutive and induced resistance decreased with salt stress but were not affected by inoculation. Conclusions. Nodule formation did not alter the negative effects of salinity on seed production or resistance to herbivory, suggesting that the benefits of biological nitrogen fixation are modest compared with the overwhelming negative effects of salt stress on soybean growth, reproduction, and ability to defend from herbivores.

Phytoremediation of waste dumping site soil and landfill leachate by using cattail (Typha latifolia)

ABSTRACT In this study, cattail (Typha latifolia) was used to remove Na+ and Cl− from polluted soil (PS) in a solid waste open dumping site. Hydroponic system was also evaluated to remove Na+ and Cl− from landfill leachate. The results indicated that the cattail grown in PS had higher biomass yield of 44.4 ± 3.29 g compared to that of control (35.3 ± 4.28 g). Nitrogen and phosphorous contents of cattails grown in PS were also higher than that of control plants, and the electrical conductivity of PS significantly decreased from 245 ± 1.40 to 51.9 ± 9.30 ms/m over the 5-week experimental duration. Na+ and Cl− contents from cattail grown on PS were 10.8 ± 1.85 and 64.7 ± 9.15 g/kg biomass, respectively. For cattails grown hydroponically in water containing leachate, nitrogen and phosphorous accumulation was 51.1 ± 5.94 and 9.32 ± 3.22 g/kg biomass, respectively. The corresponding biomass yield of these cattails was 13.5 ± 1.29 g at the end of 5 weeks. In addition, the Na+ and Cl− accumulation of 55.5 ± 4.82 and 78.2 ± 28.3 g/Kg biomass, respectively, was higher in hydroponic cattails grown in this study. Overall, the results suggest the effectiveness of cattails for phytoremediation of contaminated soil and the high efficiency of hydroponic system for nutrient and salinity removal compared to the conventional soil test. GRAPHICAL ABSTRACT