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Papers by Marie-Claude Fortin

Sensing in the roots of higher plants has long been recognized to be restricted mainly to gravitr... more Sensing in the roots of higher plants has long been recognized to be restricted mainly to gravitropism and thigmotropism. However, root responses to temperature gradients have not been extensively studied. We have designed experiments under controlled conditions to test if and how root direction of maize can be altered by thermal gradients perpendicular to the gravity vector. Primary roots of maize grown on agar plates exhibit positive thermotropism (curvature toward the warmer temperature) when exposed to gradients of 0.5 to 4.2°C cm⁻¹. The extent of thermotropism depends on the temperature gradient and the temperature at which the root is placed within the gradient. The curvature cannot be accounted for by differential growth as a direct effect of temperature on each side of the root.

Soil Science Society of America Journal, 1994

Soils in no-tillage management are often plowed for crop rotation or to correct a pest or soil ma... more Soils in no-tillage management are often plowed for crop rotation or to correct a pest or soil management problem. This study determined whether soil properties created by no-tillage were retained or reestablished after plowing and return to no-tillage. The study was conducted on a Capac loam (fine-loamy, mixed, mesic Aerie Ochraqualf) in East Lansing, MI. In 1986 and 1987, one each of three treatments in no-tillage since 1980 was plowed and subsequently returned to notillage (NTP86 and NTP87) and compared with conventional tillage (CT) and long-term no-tillage (NT). In all treatments, plowing, compared with NT, decreased bulk density by 0.17 to 0.28 Mg m" 3 , increased total porosity from 0.03 to 0.10 m 3 m" 3 , increased macroporosity by 0.05 to 0.13 m 3 m~\ and decreased microporosity by 0.03 to 0.05 m 3 m-\ Wheel traffic increased bulk density 0.14 to 0.18 Mg m~3 in the plowed soils but only 0.04 Mg m~3 in the NT soil. Soil surface P, K, and organic C (OC) were redistributed in the surface 200 mm by plowing, but plowing did not eliminate stratification of chemical properties in the surface 50 mm. The NTP87 treatment enhanced mineralization of N over both CT and NT by 9.8 to 18.4 g N m~3 in the surface 50 mm in 1987. Residual effects were evident 1 yr after plowing. However, 4 to 5 yr after plowing, most soil properties had returned to levels of NT, although reestablishment of C and N in the surface remained lower than NT.

Soil Science Society of America Journal, 1996

Planta, 1991

Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degr... more Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation. The magnitude of the response decreased with gradient strength. Maximum thermotropism was independent of gradient strength and pre-treatment temperature. The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature. However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths. In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses. Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector. It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.

Plant, Cell and Environment, 1989

A gravitational stimulus was used to induce the curvature of the main root of Arabidopsis thalian... more A gravitational stimulus was used to induce the curvature of the main root of Arabidopsis thaliana. The number of secondary roots increased on the convex side and decreased on the concave side of any curved main root axes in comparison with straight roots used as the control. The same phenomenon was observed with the curved main roots of plants grown on a clinostat and of mutant plants exhibiting random root orientation. The data suggest that the pattern of lateral root formation is associated with curvature but is independent of the environmental stimuli used to induce curvature.

Soil and Tillage Research, 1992

ABSTRACT A potential constraint to the no-tillage production of corn (Zea mays L.) is soil densif... more ABSTRACT A potential constraint to the no-tillage production of corn (Zea mays L.) is soil densification from lack of tillage and wheel traffic. This study examines the extent and duration of the effects of periodic (rotational) zone tillage over 3 years on selected soil physical properties and corn performance. Four tillage treatments — chisel plow (CP), no tillage (NT), and two zone-tillage (ZT) treatments were evaluated on a Riddles loam (Typic Hapludalf, fine-loamy, mixed, mesic) soil. The two ZT treatments consisted of subsoiling in the row with a Bush Hog Rotill (RT) (Bush Hog, Selma, AL) or a Paratill (PR76) (Tye, Lockney, TX) subsoiler, or full-width subsoiling with a Paraplow (PR51) set at 51 cm shank spacing. Corn followed either corn or a small grain so that residues from the previous crop were about 7–9 Mg ha−1 after harvest. Crop residues on the soil surface were less than 25% after planting in the CP treatment and in the row of the RT treatment. Corn yields were reduced by 0.7–0.9 Mg ha−1 in 1985 in the NT compared with the ZT and CP treatments. Corn yields were similar for all treatment-year combinations in 1986 and 1987. Final populations were reduced in the year of tillage for the PR treatments in 1985 and 1987, but this did not significantly affect yields. The immediate effects of subsoiling on soil physical properties were significant but not different between the two ZT treatments. Soil strength as measured by cone index approached 3.0 MPa in the NT treatment and was reduced to less than 0.5 MPa by ZT over the 30 cm sampling depth, and by CP only in the 0–10 cm soil depth. Bulk density, total and air-filled porosity, and saturated hydraulic conductivity were all improved by CP and ZT. However, CP had little effect below 10–15 cm, whereas ZT improved conditions to a soil depth of 30 cm. Zone-tillage showed some residual effects on soil properties over the 2 years following tillage. Cone index increased with time but remained below 1.0 MPa over the 30 cm sampling depth. Air-filled porosity over the range of −2 to −100 kPa matric potential declined to NT levels at all soil depths within 2 years. Bulk density and total porosity declined to NT levels in the 0–7.5 and 7.5–15 cm depths but remained significantly improved over NT in the 22.5–30 cm soil depth. Macroporosity created by ZT consolidated in the years following tillage to the extent that microporosity in the ZT treatments was significantly greater than NT. While improved soil physical conditions at depth improved corn yields only in 1985 on this soil, ZT may have potential as a partial width rotational tillage system with NT as it improves soil conditions while maintaining many conservation benefits of NT.

Applied Microbiology and Biotechnology, 2001

There is a need to develop technology to allow the remediation of soil in polar regions that have... more There is a need to develop technology to allow the remediation of soil in polar regions that have been contaminated by hydrocarbon fuel spills. Bioremediation is potentially useful for this purpose, but has not been well demonstrated in polar regions. We investigated biopiles for on-site bioremediation of soil contaminated with Arctic diesel fuel in two independent smallscale field experiments at different sites on the Arctic tundra. The results were highly consistent with one another. In biopiles at both sites, extensive hydrocarbon removal occurred after one summer. After 1 year in treatments with optimal conditions, total petroleum hydrocarbons were reduced from 196 to below 10 mg per kg of soil at one site, and from 2,109 to 195 mg per kg of soil at the other site. Addition of ammonium chloride and sodium phosphate greatly stimulated hydrocarbon removal and indicates that biodegradation was the primary mechanism by which this was achieved. Inoculation with cold-adapted, mixed microbial cultures further stimulated hydrocarbon removal during the summer immediately following inoculation. At one site, soil temperature was monitored during the summer season, and a clear plastic cover increased biopile soil temperature, measured as degree-day accumulation, by 30-49%. Our results show that on-site bioremediation of fuel-contaminated soil at Arctic tundra sites is feasible.

Soil and Tillage Research, 2000

The fertile, but naturally poorly drained soils of the western Fraser Valley in British Columbia,... more The fertile, but naturally poorly drained soils of the western Fraser Valley in British Columbia, Canada are located in an area subject to about 1200 mm of rainfall annually. These soils were under intensive conventional tillage practices for years, which contributed to their poor in®ltrability, low organic matter, and overall poor structure. Development of tillage practices that incorporate winter cover crops and reduce traf®c in spring is required to reduce local soil degradation problems. The objective of this study was to determine short-term responses of soil physical properties to fall and spring tillage (ST) and fall and no spring tillage (NST) systems, both using spring barley (Hordeum vulgare L.) and winter wheat (Triticum aestivum L.) as winter cover crops. Field experiments were conducted for 3 years following seeding of the winter cover crops in fall 1992 on a silty clay loam Humic Gleysol (Mollic Gleysol in FAO soil classi®cation). Average aeration porosity was 0.15 m 3 m À3 on NST and 0.22 m 3 m À3 on ST, while bulk density was 1.22 Mg m À3 on NST and 1.07 Mg m À3 on ST at the 0±7.5 cm depth. Neither of these two soil properties should limit seedling and root growth. After ST, mechanical resistance was consistently greater for 500±1000 kPa in NST than in ST, but never reached value of 2500 kPa considered limiting for root growth. The NST system did not increase soil water content relative to ST, with soil water contents being similar at 10 and 40 cm depth in all years. In 2 out of 3 years NST soil was drier at the 20 cm depth than was ST soil. Three years of NST did not result in a signi®cant changes of aggregate stability relative to ST. This experiment showed that limiting tillage operations to the fall did not adversely affect soil physical conditions for plant growth in a humid maritime climate. # : S 0 1 6 7 -1 9 8 7 ( 0 0 ) 0 0 0 9 2 -1

Sensing in the roots of higher plants has long been recognized to be restricted mainly to gravitr... more Sensing in the roots of higher plants has long been recognized to be restricted mainly to gravitropism and thigmotropism. However, root responses to temperature gradients have not been extensively studied. We have designed experiments under controlled conditions to test if and how root direction of maize can be altered by thermal gradients perpendicular to the gravity vector. Primary roots of maize grown on agar plates exhibit positive thermotropism (curvature toward the warmer temperature) when exposed to gradients of 0.5 to 4.2°C cm⁻¹. The extent of thermotropism depends on the temperature gradient and the temperature at which the root is placed within the gradient. The curvature cannot be accounted for by differential growth as a direct effect of temperature on each side of the root.

Soil Science Society of America Journal, 1994

Soils in no-tillage management are often plowed for crop rotation or to correct a pest or soil ma... more Soils in no-tillage management are often plowed for crop rotation or to correct a pest or soil management problem. This study determined whether soil properties created by no-tillage were retained or reestablished after plowing and return to no-tillage. The study was conducted on a Capac loam (fine-loamy, mixed, mesic Aerie Ochraqualf) in East Lansing, MI. In 1986 and 1987, one each of three treatments in no-tillage since 1980 was plowed and subsequently returned to notillage (NTP86 and NTP87) and compared with conventional tillage (CT) and long-term no-tillage (NT). In all treatments, plowing, compared with NT, decreased bulk density by 0.17 to 0.28 Mg m" 3 , increased total porosity from 0.03 to 0.10 m 3 m" 3 , increased macroporosity by 0.05 to 0.13 m 3 m~\ and decreased microporosity by 0.03 to 0.05 m 3 m-\ Wheel traffic increased bulk density 0.14 to 0.18 Mg m~3 in the plowed soils but only 0.04 Mg m~3 in the NT soil. Soil surface P, K, and organic C (OC) were redistributed in the surface 200 mm by plowing, but plowing did not eliminate stratification of chemical properties in the surface 50 mm. The NTP87 treatment enhanced mineralization of N over both CT and NT by 9.8 to 18.4 g N m~3 in the surface 50 mm in 1987. Residual effects were evident 1 yr after plowing. However, 4 to 5 yr after plowing, most soil properties had returned to levels of NT, although reestablishment of C and N in the surface remained lower than NT.

Soil Science Society of America Journal, 1996

Planta, 1991

Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degr... more Thermotropism in primary roots of Zea mays L. was studied with respect to gradient strength (degrees C cm-1), temperature of exposure within a gradient, pre-treatment temperature, and gravitropic stimulation. The magnitude of the response decreased with gradient strength. Maximum thermotropism was independent of gradient strength and pre-treatment temperature. The range of temperature for positive and negative thermotropism did not change with pre-treatment temperature. However, the exact range of temperatures for positive and negative thermotropism varied with gradient strengths. In general, temperatures of exposure lower than 25 degrees C resulted in positive tropic responses while temperatures of exposure of 39 degrees C or more resulted in negative tropic responses. Thermotropism was shown to modify and reverse the normal gravitropic curvature of a horizontal root when thermal gradients were applied opposite the 1 g vector. It is concluded that root thermotropism is a consequence of thermal sensing and that the curvature of the primary root results from the interaction of the thermal and gravitational sensing systems.

Plant, Cell and Environment, 1989

A gravitational stimulus was used to induce the curvature of the main root of Arabidopsis thalian... more A gravitational stimulus was used to induce the curvature of the main root of Arabidopsis thaliana. The number of secondary roots increased on the convex side and decreased on the concave side of any curved main root axes in comparison with straight roots used as the control. The same phenomenon was observed with the curved main roots of plants grown on a clinostat and of mutant plants exhibiting random root orientation. The data suggest that the pattern of lateral root formation is associated with curvature but is independent of the environmental stimuli used to induce curvature.

Soil and Tillage Research, 1992

ABSTRACT A potential constraint to the no-tillage production of corn (Zea mays L.) is soil densif... more ABSTRACT A potential constraint to the no-tillage production of corn (Zea mays L.) is soil densification from lack of tillage and wheel traffic. This study examines the extent and duration of the effects of periodic (rotational) zone tillage over 3 years on selected soil physical properties and corn performance. Four tillage treatments — chisel plow (CP), no tillage (NT), and two zone-tillage (ZT) treatments were evaluated on a Riddles loam (Typic Hapludalf, fine-loamy, mixed, mesic) soil. The two ZT treatments consisted of subsoiling in the row with a Bush Hog Rotill (RT) (Bush Hog, Selma, AL) or a Paratill (PR76) (Tye, Lockney, TX) subsoiler, or full-width subsoiling with a Paraplow (PR51) set at 51 cm shank spacing. Corn followed either corn or a small grain so that residues from the previous crop were about 7–9 Mg ha−1 after harvest. Crop residues on the soil surface were less than 25% after planting in the CP treatment and in the row of the RT treatment. Corn yields were reduced by 0.7–0.9 Mg ha−1 in 1985 in the NT compared with the ZT and CP treatments. Corn yields were similar for all treatment-year combinations in 1986 and 1987. Final populations were reduced in the year of tillage for the PR treatments in 1985 and 1987, but this did not significantly affect yields. The immediate effects of subsoiling on soil physical properties were significant but not different between the two ZT treatments. Soil strength as measured by cone index approached 3.0 MPa in the NT treatment and was reduced to less than 0.5 MPa by ZT over the 30 cm sampling depth, and by CP only in the 0–10 cm soil depth. Bulk density, total and air-filled porosity, and saturated hydraulic conductivity were all improved by CP and ZT. However, CP had little effect below 10–15 cm, whereas ZT improved conditions to a soil depth of 30 cm. Zone-tillage showed some residual effects on soil properties over the 2 years following tillage. Cone index increased with time but remained below 1.0 MPa over the 30 cm sampling depth. Air-filled porosity over the range of −2 to −100 kPa matric potential declined to NT levels at all soil depths within 2 years. Bulk density and total porosity declined to NT levels in the 0–7.5 and 7.5–15 cm depths but remained significantly improved over NT in the 22.5–30 cm soil depth. Macroporosity created by ZT consolidated in the years following tillage to the extent that microporosity in the ZT treatments was significantly greater than NT. While improved soil physical conditions at depth improved corn yields only in 1985 on this soil, ZT may have potential as a partial width rotational tillage system with NT as it improves soil conditions while maintaining many conservation benefits of NT.

Applied Microbiology and Biotechnology, 2001

There is a need to develop technology to allow the remediation of soil in polar regions that have... more There is a need to develop technology to allow the remediation of soil in polar regions that have been contaminated by hydrocarbon fuel spills. Bioremediation is potentially useful for this purpose, but has not been well demonstrated in polar regions. We investigated biopiles for on-site bioremediation of soil contaminated with Arctic diesel fuel in two independent smallscale field experiments at different sites on the Arctic tundra. The results were highly consistent with one another. In biopiles at both sites, extensive hydrocarbon removal occurred after one summer. After 1 year in treatments with optimal conditions, total petroleum hydrocarbons were reduced from 196 to below 10 mg per kg of soil at one site, and from 2,109 to 195 mg per kg of soil at the other site. Addition of ammonium chloride and sodium phosphate greatly stimulated hydrocarbon removal and indicates that biodegradation was the primary mechanism by which this was achieved. Inoculation with cold-adapted, mixed microbial cultures further stimulated hydrocarbon removal during the summer immediately following inoculation. At one site, soil temperature was monitored during the summer season, and a clear plastic cover increased biopile soil temperature, measured as degree-day accumulation, by 30-49%. Our results show that on-site bioremediation of fuel-contaminated soil at Arctic tundra sites is feasible.

Soil and Tillage Research, 2000

The fertile, but naturally poorly drained soils of the western Fraser Valley in British Columbia,... more The fertile, but naturally poorly drained soils of the western Fraser Valley in British Columbia, Canada are located in an area subject to about 1200 mm of rainfall annually. These soils were under intensive conventional tillage practices for years, which contributed to their poor in®ltrability, low organic matter, and overall poor structure. Development of tillage practices that incorporate winter cover crops and reduce traf®c in spring is required to reduce local soil degradation problems. The objective of this study was to determine short-term responses of soil physical properties to fall and spring tillage (ST) and fall and no spring tillage (NST) systems, both using spring barley (Hordeum vulgare L.) and winter wheat (Triticum aestivum L.) as winter cover crops. Field experiments were conducted for 3 years following seeding of the winter cover crops in fall 1992 on a silty clay loam Humic Gleysol (Mollic Gleysol in FAO soil classi®cation). Average aeration porosity was 0.15 m 3 m À3 on NST and 0.22 m 3 m À3 on ST, while bulk density was 1.22 Mg m À3 on NST and 1.07 Mg m À3 on ST at the 0±7.5 cm depth. Neither of these two soil properties should limit seedling and root growth. After ST, mechanical resistance was consistently greater for 500±1000 kPa in NST than in ST, but never reached value of 2500 kPa considered limiting for root growth. The NST system did not increase soil water content relative to ST, with soil water contents being similar at 10 and 40 cm depth in all years. In 2 out of 3 years NST soil was drier at the 20 cm depth than was ST soil. Three years of NST did not result in a signi®cant changes of aggregate stability relative to ST. This experiment showed that limiting tillage operations to the fall did not adversely affect soil physical conditions for plant growth in a humid maritime climate. # : S 0 1 6 7 -1 9 8 7 ( 0 0 ) 0 0 0 9 2 -1