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Coincidence of heat stress with reproductive stages of cotton accelerates phenology and deteriorates the quality of cotton fiber. A field study was conducted for 2 years to investigate the benefici...

Water and nitrogen (N) are the two most important factors influencing the growth and yield of oat (Avena sativa). A pot culture study was conducted to determine the physiological and biomass production of contrasting oat genotypes to water and N supply conditions. With sufficient water, biomass yield of the naked ‘Shadow’ was 12.4% and 10.0% greater than ‘Bia’ in the treatments 750 and 1250 mg N pot−1, respectively, but ‘Bia’ produced greater grain yield than ‘Shadow’. Under severe water stress conditions, increasing N supply decreased PN mainly due to the reduction of gs and E. ‘Shadow’ had higher chlorophyll and leaf N than ‘Bia’, while there were no differences in plant total N, NuptE and NUE. With increasing N application and water stress, WUEL and WUEP both increased. NUE was inversely related with increasing N rates and water stress levels, resulting in a trade-off relationship between WUEP and NUE.

A three-site-year field experiment was conducted to determine nitrogen (N), phosphorus (P), and potassium (K) fertilizer effects on grain filling dynamics and yield formation of high-yielding summer corn (Zea mays L.) in a wheat (Triticum aestivum L.)-corn double crop cropping system. Application of combined NPK fertilizers resulted in the greatest grain yield, largest grain number and grain weight when compared with the treatments receiving N, NP, or NK. Grain filling rate and duration, grain volume, and grain yield increased with NPK rates; however, doubling the rate of 180 kg N ha−1, 40 kg P ha−1, and 75 kg K ha−1 fertilizer only led to minimal increases in grain filling rate (0.8%), grain filling duration (1.6%), grain volume (1.3%) and grain yield (0.4%). Our results suggested that for the high-yielding summer corn, a combined NPK fertilization is required to enhance grain filling and yield, and that under well-fertilized circumstances, limited increases in both grain filling and sink capacity might ...

Wheat cultivars (‘AC Barrie’, ‘Brook Field’, ‘Hoffman’, and ‘Norwell’) with different protein concentrations were compared under four nitrogen (N) levels (0, 50, 100 and 150 kg ha−1) in an environment-controlled greenhouse, and the same experiment with an additional N level (200 kg N ha−1) was repeated in the field in 2007. In the greenhouse experiment, application of 100 kg N ha−1 resulted in significantly greater grain yield due mainly to higher number of grains per spike and heavier mean grain weight; in the field study, the 150 kg N ha−1 treatment produced the greatest yield (P

Global crop production systems are challenged by the increasing areas of saline soil in arid and semi-arid regions. Two naked oat (Avena sativa L.) lines (‘VAO-7’ and ‘VAO-24’) with distinct seedling tolerance to salinity were subjected to six levels of salt concentrations in a controlled greenhouse, and the response of yield and yield components to salinity stress was determined. The salt treatments 50, 100, 150, 200, and 250 mM sodium chloride (NaCl) (corresponding to EC: 3.42, 6.74, 9.66, 12.40, 15.04 dS m−1) imposed through modified Hoagland solution. Plain Hoagland was used as control. Complete nutrient elements were provided during the entire growth period. At maturity, the number of tillers with emerged heads was counted; the plant was then harvested and separated into shoots, seeds, and roots. Both plant height and days to maturity were shortened with increasing salt stress. Among the yield components, spikelet, tiller number, and grain dry weight per plant were significantly reduced by i...

Short daylength (SD) is the main environment-induced factor leading to fall dormancy (FD) in alfalfa (Medicago sativa L.). However, the physiological mechanisms causing varietal differences in shoot growth and fall dormancy of alfalfa crop are not fully understood. The objective of this research was to explore the physiological principles regulating FD in alfalfa by examining phytochrome B (PhyB) and abscisic acid (ABA) contents in response to photoperiodic reaction and fall dormancy. Three alfalfa varieties having different levels of fall dormancy were examined for ABA and PhyB concentrations under three photoperiod conditions (8, 12, and 16 h photoperiod). Our results showed that the leaf PhyB concentration was the greatest in the highly dormant variety, intermediate in semi-dormant, and the lowest in non-dormant varieties. Across all the varieties, PhyB concentration under 8-h photoperiod was 9.2% and 37.4% higher than those under 12-h and 16-h photoperiod (LD), respectively. Accordingly, the ...

In order to make regulations that safeguard food and the environment, an understanding of the fate oftransgenes from genetically modified (GM) plants is of crucial importance. A compost experiment including mature transgenic corn plants and seeds of event Bt 176 (Zea mays L.) was conducted to trace the fate of the transgene cryIA(b) during the period of composting. In bin 1, shredded corn plants including seeds were composted above a layer of cow manure and samples from the corn layer were collected at intervals during a 12-month period. The samples were tested for the transgene persistence and microbial counts and also the compost was monitored for temperature. In bin 2, piles of corn seeds, surrounded by sheep manure and straw, were composted for 12 months. A method combining nested polymerase chain reaction (PCR) and southern hybridization was developed for detection of the transgene in compost. The detection sensitivity was 200 copies of the transgene per gram of dry composted corn material. Composting commenced on day 0, and the transgene was detected in specimens from bin 1 on days 0 and 7 but not on day 14 or thereafter. The transgene in corn seeds was not detectable after 12 months of composting in bin 2. Temperatures in both bins rose to about 50 degrees C within 2 weeks and remained above that temperature for about 3 months, even when the ambient temperature dropped below -20 degrees C. Extracts from compost were inoculated onto culture plates and then were incubated at 23 to 55 degrees C. Within the first 2 weeks of composting in bin 1, the counts of bacteria incubated at 55 degrees C increased from 3.5 to 7.5 log10, whereas those incubated at 23 degrees C remained at about 7.5 log10. The counts of fungi incubated at 45 degrees C increased slightly from 2.5 to 3.1 log10, but those incubated at 23 degrees C decreased from 6.3 to 3.0 log10. The rapid degradation of the transgene during composting of Bt corn plants suggested that the composting process could be used for safe disposal of transgenic plant wastes.

The SPAD chlorophyll meter was found to be a reliable, quick, and non-destructive tool used for directly measuring leaf chlorophyll and indirectly assessing the proportional parameter of leaf, and by extension, plant nitrogen (N) status. The meter has been used successfully to assess leaf N in conventional maize crops, but it has not been used with new maize (Zea mays L.) genotypes containing leafy (L) and reduced stature (RS) traits. SPAD meter readings were collected on the uppermost fully developed leaves (before silking) and on the ear leaf (after silking) of field grown maize genotypes with and without the L and RS traits. The experiment was conducted during 1996 and 1997 at two sites in Eastern Canada (Ottawa and Montreal). At each site in each year, a split plot arrangement of two treatment factors was used in a randomized complete block design with four blocks. The main plot treatments were levels of N (0, 85, 170, and 255 kg ha−1), with six maize genotypes as subplot treatments. The hybrids inclu...

Available soil mineral nitrogen (N) varies both temporally and spatially. These variations affect field‐scale N‐use efficiency. A field study was conducted for three years to investigate spatial variability in available soil mineral N within uniform research plots in relation to leaf greenness or chlorophyll content (plant N sufficiency) and yield. Variations within the plot in available soil mineral N sampled at the 6‐ligule stage was related to N fertility: the higher the fertilizer N levels, the higher the variability. The standard deviation for the 200 kg N ha‐1 treatment was up to five times higher than the unfertilized control treatment. The nitrate (NO3)‐N accounted for 70 to 80% of soil mineral N in fertilized plots compared to 50 to 60% in unfertilized control plots. The variability in grain yield of individual maize (Zea mays L.) plants within a plot was inversely related to soil N fertility: the higher the fertilizer N levels, the lower the yield variability (at 100 or 200 kg N ha‐1, y...

Optical emission spectroscopy provides a rapid and precise method for determining nitrogen (N) as the 15N/14N ratios of 15N‐enriched plant and/or soil samples. The objective of this study was to te...

Nitrogen use efficiency (NUE) of N fertilizer can be accurately estimated by tracing the fate of soil applied 15N‐labeling. However, the quantity of N remobilization from non‐kernel components into kernels in maize (Zea mays L.) plants is difficult to determine. A field experiment involving stem infusion with four levels of enriched 15N solution plus non‐infusion or infusion with water was conducted at Ottawa (45°22'N, 75°43'W), Canada to determine the effect of 15N atom % enrichment (a.e.) on physiological processes associated with NUE. At anthesis, 30 mL of 35.7 mmol N solution as 15NH4 15NO3 at 5.0 (N05), 33.0 (N33), 66.0 (N66) and 99.2 (N99) 15N% a.e. was infused into the internode below the primary cob. The control plants were infused with distilled water. Photosynthesis was measured at 2, 4, 6, 24 h and 1 wk after infusion. Plants were sampled and separated into components at 4 d after anthesis (D4A) and at physiological maturity (PM). Dry weight, total N concentration, NH4‐ and NO3‐N, and ...

Nitrogen (N) use efficiency (NUE) of fertilizer N can be accurately estimated by tracing the fate of soil applied labelled fertilizer, but the quantity of N remobilization from non‐kernel components into kernels in maize (Zea mays L.) plants is difficult to determine. A field experiment involving stem infusion with labelled 15N solution was conducted at Ottawa, Ontario (45°22'N, 75°43'W) for two years to determine whether stem infused 15N could be used to quantify N remobilization and the contribution of remobilized N to the grain. A current stay‐green commercial hybrid was grown at three fertilizer N rates and infused with 30 mL 15N solution [35.7 mmol N as 15NH4 15NO3 at 99.2 15N% atom enrichment (a.e.)] into the internode below the primary cob at anthesis. The control plants were infused with distilled water. Sampling occurred at 3 d, 2 wk and 5 wk after anthesis and at physiological maturity. Each plant was subdivided into ten components. Dry weight, total N concentration and 15N% a.e. were d...

Optical emission spectroscopy provides a rapid and precise method for determining 15N/14N ratios of 15N‐enriched plant and/or soil samples. The objective of this study was to determine the effect of an indicator added in the distillation solution on the success rate of tube lighting in the optical emission spectrometer over a large range of N concentration in 15N enriched plant samples. One‐hundred‐eighty plant samples with large ranges of N concentration (4 to 30 g.kg‐1 dry weight) and 15N atom enrichment (0.368 to 1.635%) were analyzed. Our data suggest that there was no difference in the success rate of tube lighting in emission spectroscopy and in 15N/14N ratio measured between samples prepared with and without addition of indicator in the distillation solution.

Choice of minimum size of nitrogen (15N) microplots is essential in studies of maize (Zea mays L.) N uptake, translocation, assimilation, and accumulation patterns using the 15N isotopic technique. The objectives of this field experiment were to determine if: i) plants adjacent to restricted 15N microplots (0.76 m × 0.23 m × 0.25 m deep, centred on a plant) were 15N‐enriched, ii) growth of plants in microplots was hampered, and iii) the estimated fertilizer N recovery (FNR) was lower than that previously reported. There was no detectable enrichment by applied 15N in maize plants adjacent to the microplots. Root and aboveground biomass and N content of plants in the microplots were similar to plants in the main plot at harvest (P>0.1). The FNR in the aboveground plants was 29% for 200 kg N ha‐1 and 38% for 100 kg N ha‐1 treatment with 18 and 26% in the corresponding grains. These values were similar to those reported in the literature where larger non‐restricted or restricted microplots were used....

The peduncle perfusion system has been used successfully to evaluate plant responses to post‐anthesis plant growth regulators (PGR) and nitrogen (N) applied through the peduncle under greenhouse conditions. No experiment with this technique has been conducted in the field. Because environmental conditions in the field and in the greenhouse are very different the utility of this technique in the field is still unknown. The objectives of this study were to evaluate: i) the overall applicability of the peduncle perfusion technique in the field, and ii) the responses of barley grain protein concentration to grain‐filling N and ethephon application through a peduncle perfusion system under field conditions. The perfusion technique floods the peduncle interior with a selected solution for periods of weeks to months. The plants were allowed to take up urea in one of two concentrations (15 and 30 mM N) or ethephon, a PGR, at 15 μM from the peduncle for 29 days. The total volume of solution taken up by th...

Nitrogen (N) or growth regulator application to small grain cereals near anthesis has been demonstrated to alter grain fill and grain yield, the protein yield and nutritional quality may also be modified by these management factors. The objective of this study was to determine whether delivery of N, growth regulator, or sucrose solutions into greenhouse‐grown barley (Hordeurn vulgare L. cv. Leger) or wheat (Triticum aestivum L. cv. Katepwa), plants through peduncle perfusion altered the amino acid composition of the grain. The following treatments were tested: N (25 and 50 mM), chlormequat (30 μM), ethephon (15 μM), N + chlormequat, N + ethephon, detillering + N, sucrose (250 mM), distilled water check, and non‐perfused check. Perfusion lasted 30 d beginning 5 to 8 d after spike emergence. Addition of N via peduncle perfusion increased protein concentrations and concentrations of all amino acids in both barley and wheat when expressed in terms of grain dry matter. Protein yield and lysine content...

Field experiments were conducted in summer 1992 on the Central Experimental Farm, Ottawa (45°22'N, 75°43'W) to determine whether a stem infusion technique developed for maize under controlled conditions was applicable to field‐grown maize and to evaluate whether providing sucrose in solution at silking via stem infusion altered plant source‐sink relationships sufficiently to increase kernel set. The higher and more variable evaporative demand and more difficult installation under field conditions dictated modifications to the stem infusion apparatus to prevent leakage and to facilitate assembly prior to field set‐up. A range of several field parameters were tested to identify conditions that would maximize infusion of sucrose solution: raising the syringe barrel height increased the volume of solution uptake; the largest amount of sucrose was taken up using a concentration of 150 g sucrose L‐1, and consecutive multiple infusions of the same plant increased solution uptake. Solution uptake was fou...