• Canada
• 010606 plant biology & botany close

Concentrations of a metallothionein-like protein (MTLP) in Tubifex tubifex were consistent throughout the various life stages with no significant variation associated with reproductive stage. The mean concentration from cocoon through 10 weeks of age was 2.5 (+/-0.6) nmol MTLP/g. T. tubifex was subjected to a number of potential environmental stressors to determine whether MTLP production could be induced in the absence of metal exposure. There were no significant differences in the concentrations of MTLP between the controls and worms subjected to decreased food supply, increased handling, or reduced dissolved oxygen at a given exposure temperature. However, at 12 degrees C T. tubifex had significantly (P < 0.01) higher MTLP than T. tubifex held at 23 degrees C. There were also significant differences in wet weight and reproduction at the two temperatures, which may have implications for the levels of MTLP.

Randhawa, H. S., Graf, R. J., Fox, S. L. and Sadasivaiah, R. S. 2015. AAC Proclaim general purpose spring wheat. Can. J. Plant Sci. 95: 1265–1269. AAC Proclaim is a soft red spring wheat cultivar eligible for the Canada Western General Purpose (CWGP) wheat class. Evaluated in 18 trials grown over 2 yr in the General Purpose Wheat Cooperative Registration trial, AAC Proclaim yielded significantly lower than the CWGP checks, AC Andrew and Pasteur, and was 1 and 5 d earlier maturing, respectively. AAC Proclaim was significantly taller than the checks, but had similar straw strength. Test weight was higher than the checks and kernel mass was similar to AC Andrew. Based on visual assessments and deoxynivalenol testing over 3 yr, AAC Proclaim was rated as resistant to Fusarium head blight. It also expressed resistance to the prevalent races of leaf rust and moderate resistance to the prevalent races of stem rust and loose smut. AAC Proclaim showed susceptibility to infection by stripe rust and common bunt.

Fourteen clones of hybrid poplar were inoculated with 19 isolates of Septoria musiva Peck under greenhouse conditions to determine the magnitude of the clone, isolate, and clone × isolate interaction effects. Septoria musiva isolates were collected from five geographic areas, two symptoms (canker and leaf spot), and two host types (native species and hybrid poplar). The hybrid poplar clones were classified by parent type ( Populus deltoides Bartr. ex Marsh., Populus laurifolia Lebed. × Populus nigra L., and P. deltoides × (P. laurifolia × P. nigra)). There were no significant differences among geographic areas (p = 0.443), symptoms (p = 0.842), or hosts (p = 0.304) of origin for the 19 isolates nor significant differences among the three parent types (p = 0.089). Clone, isolate, and clone × isolate interaction effects were all significant, accounting for 65%, 15%, and 18%, respectively, of the explained variation. These results indicate that clones rather than parent types should be the focus of resistance screening programs and that the pathosystem should be stable given the relatively small clone × isolate interaction. These results also indicate that a single isolate should be sufficient for preliminary screening of disease resistance in hybrid poplars.

Blackleg (Phoma leaf spot), caused by the ascomycete Leptosphaeria spp. (anamorph: Phoma lingam), is a serious yield-limiting factor in canola. Leptosphaeria spp. populations are highly diverse and display differential interactions with canola cultivars, ranging from hypersensitive-like reactions to partial resistance and susceptibility. Leptosphaeria biglobosa encompasses weakly aggressive isolates and can be found late in the season towards maturity stages of the crop while other isolates from Leptosphaeria maculans are highly aggressive and can be detected throughout the season. In an earlier study, we showed the primary involvement of lignin in the containment of the progress of Phoma leaf spot symptoms around the infection sites by comparing the reaction of three different cultivars with a set of isolates with various levels of aggressiveness. The present investigation reports on further characterization of the host responses to L. biglobosa and L. maculans isolates used individually or subsequently ...

AbstractThe rapid A‐Ci response (RACiR) technique alleviates limitations of measuring photosynthetic capacity by reducing the time needed to determine the maximum carboxylation rate (Vcmax) and electron transport rate (Jmax) in leaves. Photosynthetic capacity and its relationships with leaf development are important for understanding ecological and agricultural productivity; however, our current understanding is incomplete. Here, we show that RACiR can be used in previous generation gas exchange systems (i.e., the LI‐6400) and apply this method to rapidly investigate developmental gradients of photosynthetic capacity in poplar. We compared RACiR‐determined Vcmax and Jmax as well as respiration and stomatal conductance (gs) across four stages of leaf expansion in Populus deltoides and the poplar hybrid 717‐1B4 (Populus tremula × Populus alba). These physiological data were paired with leaf traits including nitrogen concentration, chlorophyll concentrations, and specific leaf area. Several traits displayed developmental trends that differed between the poplar species, demonstrating the utility of RACiR approaches to rapidly generate accurate measures of photosynthetic capacity. By using both new and old machines, we have shown how more investigators will be able to incorporate measurements of important photosynthetic traits in future studies and further our understanding of relationships between development and leaf‐level physiology.

The supply of available nitrogen (N), phosphorus (P), and sulfur (S) to spring wheat as influenced by pea or lentil as the previous rotational crop was assessed at two field research sites over two years in Saskatchewan, Canada. Under conditions of low soil fertility, cereals grown on field pea stubble produced higher grain yields and accumulated more N than did cereals grown on lentil stubble. This result corresponded with significantly higher soil-supply rates of nitrate and phosphate measured over eight weeks in the pea-stubble plots using anion-exchange membrane (PRS) probes. However, under conditions where soil N availability was high, cereal crop yields and N uptake on pea and lentil stubble were similar.

Floral cycles and spadix temperatures were recorded for two species of Syngonium: Syngonium schottianum Wendl. ex Schott (section Cordatum) and Syngonium angustatum Schott (section Syngonium). Both species exhibited a 3-day flowering cycle, beginning with stigma receptivity and opening of the spathe the first day, the female phase continues over the second day, and the male phase continues over the third day. These species displayed two distinct patterns of heat production during flowering. In S. schottianum, the spadix warmed up twice during the beginning of the second and third nights, but in S. angustatum, the spadix warmed up twice the second day, once the second night, and once the third day. These different thermogenic cycles are discussed in regard to other genera that are phylogenetically close or sharing similar flowering and thermogenic cycles.

Chytyk, C. J., Hucl, P. J. and Gray, G. R. 2011. Leaf photosynthetic properties and biomass accumulation of selected western Canadian spring wheat cultivars. Can. J. Plant Sci. 91: 305–314. Current studies indicate wheat straw as a viable source for the production of cellulosic ethanol. Since photosynthetic performance impacts the overall success of the mature plant, this study aimed to measure the photosynthetic vigour of 11 spring wheat cultivars during field development as well as their biomass composition at maturity to determine which would be optimum for ethanol production. All cultivars had similar maximal quantum yields of photosystem II photochemistry (FV/FM), normalized difference vegetation index and biomass composition in the field. However, differences were observed in photosynthetic rate, with McKenzie having the highest light-saturated maximal rate of CO2 uptake (A max) and apparent quantum yield of CO2 uptake (Φapp CO2), while also having the best water use efficiency. Snowbird was found to have the lowest CO2-compensation point (Γ*) and A max. Upon subjecting wheat samples to photoinhibitory conditions, McKenzie and Kyle were found to be the most resistant and susceptible, respectively, with a difference of 11% in FV/FM. Abundance of xanthophyll pigments were not found to be a contributing cause to differential photoinhibitory resistance as there was not a noticeable difference between cultivars. Although some cultivars were found to have enhanced photosynthetic traits over others, these were slight and did not contribute to changes in plant biomass. However, McKenzie did present a higher cellulose content, which would be favourable for ethanol production.

Abstract Studies were conducted to examine the effects of row spacing and stubble height on surface soil water content, water use, yield, and water use efficiency of canola and wheat in the drier regions of the Canadian prairies. For this purpose, randomized complete block design trials were implemented separately in canola and wheat fields at Central Butte and Swift Current in the Brown soil zone of southwestern Saskatchewan. At each experimental site, two factors and two levels for each factor, i.e., 30- and 60-cm row spacing and 15- and 30-cm stubble heights, were included. Wider row spacing and taller stubble generally increased soil water content for the surface 0–30 cm soil depth, and taller stubble often had greater spatial variability of surface soil water content at both locations. Row spacing or stubble height had minimal effect on water use for both crops at both locations over the two years (2012 and 2013). Yield and water use efficiency of 30-cm row spacing were 1.3–1.6 (Central Butte) and 1.0–1.2 (Swift Current) times greater than those of 60-cm row spacing. Stubble height had little effects on yield and water use efficiency. There were no interactions of row spacing and stubble height on water use, yield, and water use efficiency for either crop. Overall, 30-cm row spacing and 30-cm stubble tended to increase surface soil water content, yield, and water use efficiency for most crop type, year, and site combinations.