Neal Adam - Academia.edu (original) (raw)
Papers by Neal Adam
Industrial Crops and Products, 2007
Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for comm... more Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for commercial oilseed production. Understanding the minimum temperatures for germination and seedling growth is important for determining potential areas for lesquerella production. The objectives of this study were to determine the cardinal temperatures for germination and seedling growth, and to screen ecotypes for germination and growth characteristics. A temperature gradient table arrangement was used to observe seed germination over a range of temperatures, and time to germination and shoot appearance. Times to 5 mm root length and 5 mm shoot length were also measured to assess cardinal temperatures for seedling survival and growth. Two different species were examined, L. fendleri and a species we refer to as 'L. pallida aff.' because it differed from typical L. pallida plants in chromosome number and in oil quality. We concluded that both germination and growth of L. pallida aff. occurred fastest at 22 • C, whereas L. fendleri germinated earlier at 18 • C, but grew faster at 22 • C. L. pallida aff. also had lower germination than L. fendleri over the range studied. Non-dormant seeds of improved lines of L. fendleri had better performance at temperatures above 22 • C than did unimproved accessions. Lines of L. fendleri selected for high oil content and salt tolerance had similar temperature requirements for germination except for improved line WCL-LO3, the current line being used in production. This line had optimal temperatures 6 • C higher for germination and growth than the other improved lines. Accessions of L. fendleri collected from elevations above 2000 m performed better at warmer temperatures, whereas those collected from elevations below 2000 m tended to perform better at cooler temperatures. Dormant seeds of L. fendleri germinated more quickly at low temperatures and had lower base (<3 • C) and optimal (22 • C) temperatures than non-dormant seeds (>7 • C and 28 • C, respectively). We speculate that this partial dormancy trait allows populations of L. fendleri to exploit a wider range of temperature conditions in the wild in order to thrive in extreme environments.
Land, 2022
As atmospheric carbon dioxide concentrations, [CO2Air], continue their uncontrolled rise, the cap... more As atmospheric carbon dioxide concentrations, [CO2Air], continue their uncontrolled rise, the capacity of soils to accumulate or retain carbon is uncertain. Free-air CO2 enrichment (FACE) experiments have been conducted to better understand the plant, soil and ecosystem response to elevated [CO2], frequently employing commercial CO2 that imparts a distinct isotopic signal to the system for tracing carbon. We conducted a FACE experiment in 1998 and 1999, whereby sorghum (C4 photosynthetic pathway) was grown in four replicates of four treatments using a split-strip plot design: (i) ambient CO2/ample water (365 μmol mol−1, “Control–Wet”), (ii) ambient CO2/water stress (“Control–Dry”), (iii) CO2-enriched (560 μmol mol−1, “FACE–Wet”), and (iv) CO2-enriched/water stressed (“FACE–Dry”). The stable-carbon isotope composition of the added CO2 (in FACE treatments) was close to that of free atmosphere background values, so the subsequent similar 13C-enriched carbon signal photosynthetically fi...
Photosynthesis …, 2000
We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO 2 concent... more We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO 2 concentration, and ample and limiting N supplies, within a field experiment using free-air CO 2 enrichment (FACE). To understand how leaf age and developmental stage affected any acclimation response, measurements were made on a vertical profile of leaves every week from tillering until maturity. The response of assimilation (A) to internal CO 2 concentration (C i) was used to estimate the in vivo carboxylation capacity (Vc max) and maximum rate of ribulose-1,5-bisphosphate limited photosynthesis (A sat). The total activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and leaf content of Rubisco and the Light Harvesting Chlorophyll a/b protein associated with Photosystem II (LHC II), were determined. Elevated CO 2 did not alter Vc max in the flag leaf at either low or high N. In the older shaded leaves lower in the canopy, acclimatory decline in Vc max and A sat was observed, and was found to correlate with reduced Rubisco activity and content. The dependency of acclimation on N supply was different at each developmental stage. With adequate N supply, acclimation to elevated CO 2 was also accompanied by an increased LHC II/Rubisco ratio. At low N supply, contents of Rubisco and LHC II were reduced in all leaves, although an increased LHC II/Rubisco ratio under elevated CO 2 was still observed. These results underscore the importance of leaf position, leaf age and crop developmental stage in understanding the acclimation of photosynthesis to elevated CO 2 and nutrient stress. Abbreviations: A sat-CO 2 and light saturated rate of CO 2-uptake per unit leaf area; CL-control CO 2 and limiting nitrogen supply; FL-elevated CO 2 and limiting nitrogen supply; CH-control CO 2 and high nitrogen supply; FHelevated CO 2 and high nitrogen supply; IRGA-Infra-red gas analyzer; LHC II-light harvesting chlorophyll a/b protein primarily associated with Photosystem II; RuBP-ribulose-1,5-bisphosphate; Vc max-maximum ribulose-1,5-bisphosphate saturated rate of carboxylation in vivo
![Research paper thumbnail of Leaf nitrogen concentration of wheat subjected to elevated [CO2] and either water or N deficits](https://attachments.academia-assets.com/75805563/thumbnails/1.jpg)
](Agriculture, Ecosystems & Environment, 2000
Leaf N concentration is important because it is associated with the CO 2 assimilatory capacity of... more Leaf N concentration is important because it is associated with the CO 2 assimilatory capacity of crops, and in grasslands, it is an important determinant of forage nutritive value. Consequently, the productivity of both domestic and native animals in future global environments may be closely linked to possible changes in leaf N concentration of grasses. Since grasslands are frequently subjected to water-deficit or N-deficit conditions, it is important to investigate the interactive responses between elevated [CO 2 ] and these stress conditions. Therefore, this 4-year research program was undertaken with wheat (Triticum aestivum L.) as a model system for forage grasses, to document the potential changes in leaf N concentration in response to global environment changes. Wheat crops grown under field conditions near Phoenix, AZ, USA, were subjected to elevated [CO 2 ] and either water-deficit or N-deficit treatments using large Free Air Carbon dioxide Enrichment (FACE) arrays. Surprisingly, the elevated [CO 2 ] treatment under optimum conditions resulted in little change in leaf N concentration. Therefore, no change in the nutritive value of forage from highly managed pastures would be expected. Further, water-deficit treatment had little influence on leaf N concentration. To some extent, the lack of response to the water-deficit treatment resulted because severe deficits did not develop until late in the growing seasons. Only on one date late in the season was the water-deficit treatment found to result in decreased leaf N concentration. The low N treatment in combination with elevated [CO 2 ], however, had a large influence on leaf N concentration. Low levels of applied N resulted in decreased leaf N concentration under both [CO 2 ] treatments, but the lowest levels of leaf N concentration were obtained under elevated [CO 2 ] through much of the growing season. These results point to a potential problem with grasslands in that the nutritive value of the forage consumed by animals will be decreased under future global environment changes.
New …, 2004
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Journal of Experimental Botany, 2003
The developmental pattern of C 4 expression has been well characterized in maize and other C 4 pl... more The developmental pattern of C 4 expression has been well characterized in maize and other C 4 plants. However, few reports have explored the possibility that the development of this pathway may be sensitive to changes in atmospheric CO 2 concentrations. Therefore, both the structural and biochemical development of leaf tissue in the ®fth leaf of Sorghum bicolor plants grown at elevated CO 2 have been characterized. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) activities accumulate rapidly as the leaf tissue differentiates and emerges from the surrounding whorl. Rubisco was not expressed in a cell-speci®c manner in the youngest tissue at the base of the leaf, but did accumulate before PEPC was detected. This suggests that the youngest leaf tissue utilizes a C 3-like pathway for carbon ®xation. However, this tissue was in a region of the leaf receiving very low light and so signi®cant rates of photosynthesis were not likely. Older leaf tissue that had emerged from the surrounding whorl into full sunlight showed the normal C 4 syndrome. Elevated CO 2 had no effect on the cell-speci®c localization of Rubisco or PEPC at any stage of leaf development, and the relative ratios of Rubisco to PEPC remained constant during leaf development. However, in the oldest tissue at the tip of the leaf, the total activities of Rubisco and PEPC were decreased under elevated CO 2 implying that C 4 photosynthetic tissue may acclimate to growth under elevated CO 2 .
Industrial Crops and Products, 2007
Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for comm... more Lesquerella (Lesquerella fendleri) is a potential alternative crop that is being studied for commercial oilseed production. Understanding the minimum temperatures for germination and seedling growth is important for determining potential areas for lesquerella production. The objectives of this study were to determine the cardinal temperatures for germination and seedling growth, and to screen ecotypes for germination and growth characteristics. A temperature gradient table arrangement was used to observe seed germination over a range of temperatures, and time to germination and shoot appearance. Times to 5 mm root length and 5 mm shoot length were also measured to assess cardinal temperatures for seedling survival and growth. Two different species were examined, L. fendleri and a species we refer to as 'L. pallida aff.' because it differed from typical L. pallida plants in chromosome number and in oil quality. We concluded that both germination and growth of L. pallida aff. occurred fastest at 22 • C, whereas L. fendleri germinated earlier at 18 • C, but grew faster at 22 • C. L. pallida aff. also had lower germination than L. fendleri over the range studied. Non-dormant seeds of improved lines of L. fendleri had better performance at temperatures above 22 • C than did unimproved accessions. Lines of L. fendleri selected for high oil content and salt tolerance had similar temperature requirements for germination except for improved line WCL-LO3, the current line being used in production. This line had optimal temperatures 6 • C higher for germination and growth than the other improved lines. Accessions of L. fendleri collected from elevations above 2000 m performed better at warmer temperatures, whereas those collected from elevations below 2000 m tended to perform better at cooler temperatures. Dormant seeds of L. fendleri germinated more quickly at low temperatures and had lower base (<3 • C) and optimal (22 • C) temperatures than non-dormant seeds (>7 • C and 28 • C, respectively). We speculate that this partial dormancy trait allows populations of L. fendleri to exploit a wider range of temperature conditions in the wild in order to thrive in extreme environments.
Land, 2022
As atmospheric carbon dioxide concentrations, [CO2Air], continue their uncontrolled rise, the cap... more As atmospheric carbon dioxide concentrations, [CO2Air], continue their uncontrolled rise, the capacity of soils to accumulate or retain carbon is uncertain. Free-air CO2 enrichment (FACE) experiments have been conducted to better understand the plant, soil and ecosystem response to elevated [CO2], frequently employing commercial CO2 that imparts a distinct isotopic signal to the system for tracing carbon. We conducted a FACE experiment in 1998 and 1999, whereby sorghum (C4 photosynthetic pathway) was grown in four replicates of four treatments using a split-strip plot design: (i) ambient CO2/ample water (365 μmol mol−1, “Control–Wet”), (ii) ambient CO2/water stress (“Control–Dry”), (iii) CO2-enriched (560 μmol mol−1, “FACE–Wet”), and (iv) CO2-enriched/water stressed (“FACE–Dry”). The stable-carbon isotope composition of the added CO2 (in FACE treatments) was close to that of free atmosphere background values, so the subsequent similar 13C-enriched carbon signal photosynthetically fi...
Photosynthesis …, 2000
We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO 2 concent... more We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO 2 concentration, and ample and limiting N supplies, within a field experiment using free-air CO 2 enrichment (FACE). To understand how leaf age and developmental stage affected any acclimation response, measurements were made on a vertical profile of leaves every week from tillering until maturity. The response of assimilation (A) to internal CO 2 concentration (C i) was used to estimate the in vivo carboxylation capacity (Vc max) and maximum rate of ribulose-1,5-bisphosphate limited photosynthesis (A sat). The total activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and leaf content of Rubisco and the Light Harvesting Chlorophyll a/b protein associated with Photosystem II (LHC II), were determined. Elevated CO 2 did not alter Vc max in the flag leaf at either low or high N. In the older shaded leaves lower in the canopy, acclimatory decline in Vc max and A sat was observed, and was found to correlate with reduced Rubisco activity and content. The dependency of acclimation on N supply was different at each developmental stage. With adequate N supply, acclimation to elevated CO 2 was also accompanied by an increased LHC II/Rubisco ratio. At low N supply, contents of Rubisco and LHC II were reduced in all leaves, although an increased LHC II/Rubisco ratio under elevated CO 2 was still observed. These results underscore the importance of leaf position, leaf age and crop developmental stage in understanding the acclimation of photosynthesis to elevated CO 2 and nutrient stress. Abbreviations: A sat-CO 2 and light saturated rate of CO 2-uptake per unit leaf area; CL-control CO 2 and limiting nitrogen supply; FL-elevated CO 2 and limiting nitrogen supply; CH-control CO 2 and high nitrogen supply; FHelevated CO 2 and high nitrogen supply; IRGA-Infra-red gas analyzer; LHC II-light harvesting chlorophyll a/b protein primarily associated with Photosystem II; RuBP-ribulose-1,5-bisphosphate; Vc max-maximum ribulose-1,5-bisphosphate saturated rate of carboxylation in vivo
Agriculture, Ecosystems & Environment, 2000
Leaf N concentration is important because it is associated with the CO 2 assimilatory capacity of... more Leaf N concentration is important because it is associated with the CO 2 assimilatory capacity of crops, and in grasslands, it is an important determinant of forage nutritive value. Consequently, the productivity of both domestic and native animals in future global environments may be closely linked to possible changes in leaf N concentration of grasses. Since grasslands are frequently subjected to water-deficit or N-deficit conditions, it is important to investigate the interactive responses between elevated [CO 2 ] and these stress conditions. Therefore, this 4-year research program was undertaken with wheat (Triticum aestivum L.) as a model system for forage grasses, to document the potential changes in leaf N concentration in response to global environment changes. Wheat crops grown under field conditions near Phoenix, AZ, USA, were subjected to elevated [CO 2 ] and either water-deficit or N-deficit treatments using large Free Air Carbon dioxide Enrichment (FACE) arrays. Surprisingly, the elevated [CO 2 ] treatment under optimum conditions resulted in little change in leaf N concentration. Therefore, no change in the nutritive value of forage from highly managed pastures would be expected. Further, water-deficit treatment had little influence on leaf N concentration. To some extent, the lack of response to the water-deficit treatment resulted because severe deficits did not develop until late in the growing seasons. Only on one date late in the season was the water-deficit treatment found to result in decreased leaf N concentration. The low N treatment in combination with elevated [CO 2 ], however, had a large influence on leaf N concentration. Low levels of applied N resulted in decreased leaf N concentration under both [CO 2 ] treatments, but the lowest levels of leaf N concentration were obtained under elevated [CO 2 ] through much of the growing season. These results point to a potential problem with grasslands in that the nutritive value of the forage consumed by animals will be decreased under future global environment changes.
New …, 2004
Skip to Main Content. ...
Journal of Experimental Botany, 2003
The developmental pattern of C 4 expression has been well characterized in maize and other C 4 pl... more The developmental pattern of C 4 expression has been well characterized in maize and other C 4 plants. However, few reports have explored the possibility that the development of this pathway may be sensitive to changes in atmospheric CO 2 concentrations. Therefore, both the structural and biochemical development of leaf tissue in the ®fth leaf of Sorghum bicolor plants grown at elevated CO 2 have been characterized. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC) activities accumulate rapidly as the leaf tissue differentiates and emerges from the surrounding whorl. Rubisco was not expressed in a cell-speci®c manner in the youngest tissue at the base of the leaf, but did accumulate before PEPC was detected. This suggests that the youngest leaf tissue utilizes a C 3-like pathway for carbon ®xation. However, this tissue was in a region of the leaf receiving very low light and so signi®cant rates of photosynthesis were not likely. Older leaf tissue that had emerged from the surrounding whorl into full sunlight showed the normal C 4 syndrome. Elevated CO 2 had no effect on the cell-speci®c localization of Rubisco or PEPC at any stage of leaf development, and the relative ratios of Rubisco to PEPC remained constant during leaf development. However, in the oldest tissue at the tip of the leaf, the total activities of Rubisco and PEPC were decreased under elevated CO 2 implying that C 4 photosynthetic tissue may acclimate to growth under elevated CO 2 .