Agriculture and Agri-Food Canada

About: Agriculture and Agri-Food Canada is a facility organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Population & Soil water. The organization has 10921 authors who have published 21332 publications receiving 748193 citations. The organization is also known as: Department of Agriculture and Agri-Food.

Adaptation of Arabidopsis to nitrogen limitation involves induction of anthocyanin synthesis which is controlled by the NLA gene.

Abstract: Plants can survive a limiting nitrogen (N) supply by developing a set of N limitation adaptive responses. However, the Arabidopsis nla (nitrogen limitation adaptation) mutant fails to produce such responses, and cannot adapt to N limitation. In this study, the nla mutant was utilized to understand further the effect of NLA on Arabidopsis adaptation to N limitation. Grown with limiting N, the nla mutant could not accumulate anthocyanins and instead produced an N limitation-induced early senescence phenotype. In contrast, when supplied with limiting N and limiting phosphorus (Pi), the nla mutants accumulated abundant anthocyanins and did not show the N limitation-induced early senescence phenotype. These results support the hypothesis that Arabidopsis has a specific pathway to control N limitation-induced anthocyanin synthesis, and the nla mutation disrupts this pathway. However, the nla mutation does not affect the Pi limitation-induced anthocyanin synthesis pathway. Therefore, Pi limitation induced the nla mutant to accumulate anthocyanins under N limitation and allowed this mutant to adapt to N limitation. Under N limitation, the nla mutant had a significantly down-regulated expression of many genes functioning in anthocyanin synthesis, and an enhanced expression of genes involved in lignin production. Correspondingly, the nla mutant grown with limiting N showed a significantly lower production of anthocyanins (particularly cyanidins) and an increase in lignin contents compared with wild-type plants. These data suggest that NLA controls Arabidopsis adaptability to N limitation by channelling the phenylpropanoid metabolic flux to the induced anthocyanin synthesis, which is important for Arabidopsis to adapt to N limitation.

Nitrogen uptake and use of two contrasting maize hybrids differing in leaf senescence

Abstract: In eastern Canada, the use of fertilizer N has been identified as the most energy-consuming component of maize (Zea mays L.) grain production. As the economic and environmental costs of excessive N fertilization rise, there is an increased emphasis on selection of hybrids with greater N use efficiency (NUE; defined as the ratio of the amount of 15N recovered in grain or stover dry matter to the amount of fertilizer 15N applied to the soil in this study). Using an 15N-labelling approach, a field study was conducted on a tile-drained Brandon loam soil (Typic Endoaquoll) on the Central Experimental Farm at Ottawa, Canada (45°22′ N, 75°43′ W) in 1993 and 1994. Fertilizer N uptake and partitioning within the plant in relation to dry matter changes were monitored during development of a current stay-green maize hybrid and an older early-senescing hybrid grown with three fertilizer N levels (0, 100, 200 kg N ha-1). Dry matter, N concentration and15 N atom% enrichment of plant components were determined at five growth stages. The current stay-green hybrid, ‘Pioneer 3902’ had greater NUE than the old early-senescing hybrid, ‘Pride 5’, which was associated with 24% more dry matter production and 20% more N uptake during grain fill for Pioneer 3902. There was no indication of greater allocation of N to the grain in Pioneer 3902. Our data suggest that prolonged maintenance of green leaf area for photosynthate production during grain fill and the ability to take up available soil N later in grain filling are characteristics of maize hybrids with greater NUE.

Assessment of a Method to Measure Temporal Change in Soil Carbon Storage

Abstract: Sensitive methods are essential to resolve small changes in soil C storage, such as those attained in sequestration projects, against much larger quantities of C already present. To measure temporal changes in C storage we proposed a high-resolution method based on collecting volumetric soil cores from a microsite (4 by 7 m), marking core locations to intersperse multiple cores collected initially and in a subsequent sampling year, rigorous analytical quality control, and calculating soil C pool sizes with proper corrections for unequal soil masses. To evaluate the method, we measured the recovery of 3.64 Mg C ha -1 added as coal dust to microsites. We calculated C stored in successive soil layers of both fixed volume and equivalent mass. We inferred coal C recovery from spatial comparisons between coal-amended and unamended plots, and from temporal comparisons between soil samples collected before and after coal addition. The comparisons among C storage showed effective recovery of added coal C, but only for paired temporal differences based on calculations of organic C storage in an equivalent soil mass. With spatial comparisons, coal C became undetectable when soil thickness exceeded 35 cm. With temporal comparisons, coal C recovery ranged from 91 to 106%, provided differences were calculated for successively thicker layers of equivalent soil mass. In contrast, recovery was only 64 to 82% when temporal differences were calculated for layers of fixed soil volume. The method is useful to quantify small temporal changes in soil organic C storage within microsites, and possibly over more extensive areas with sufficient samples to characterize spatial variability.