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Kelly J.A.,Acadia University | Avery T.S.,Acadia University | Stewart D.T.,Acadia University | Cutler C.G.,Dalhousie University | And 3 more authors.
Canadian Entomologist | Year: 2013

Cucullia umbratica Linnaeus (Lepidoptera: Noctuidae), Agnippe prunifoliella Chambers (Lepidoptera: Gelechiidae), and Bryotropha plantariella Tengstrom (Lepidoptera: Gelechiidae), were significant bycatch in pheromone-based trapping systems for red-striped fireworm, Aroga trialbamaculella Chambers (Lepidoptera: Gelechiidae), in Nova Scotia, Canada. Cucullia umbratica is a European introduced species and a new macrolepidopteran recorded in continental Canada. The only previous record of this moth in North America was from the Magdalen Islands (Québec, Canada). Potential attractants for B. plantariella, A. prunifoliella, and C. umbratica are a result of this bycatch investigation. Copyright © 2013 Entomological Society of Canada. Source

Amon-Armah F.,Dalhousie University | Yiridoe E.K.,Dalhousie University | Jamieson R.,Dalhousie University | Hebb D.,Atlantic Food and Horticulture Research Center
Agroecology and Sustainable Food Systems | Year: 2015

Alternative mathematical functional forms commonly applied in modelling crop and pollution production response to nitrogen (N) fertilizer use were investigated. Data were generated using soil and water assessment tool modeling, and explicitly accounted for rotation effects on regression parameters. The Mitscherlich–Baule model best represented potato, carrot, and alfalfa yield response, while the quadratic model best described corn, winter wheat, and barley yield response to N fertilization. The quadratic functional form also best represented nitrate-N leaching response to N fertilization for most crops. Maximum economic rates of N fertilization for crops were sensitive to residual N effects of previous crops. © ,Taylor & Francis Group, LLC. Source

Thiagarajan A.,Dalhousie University | Thiagarajan A.,Laval University | Lada R.,Dalhousie University | Pepin S.,Laval University | And 3 more authors.
Journal of Plant Growth Regulation | Year: 2013

Seasonal changes in the concentration of abscisic acid (ABA) in current-year needles of two different genotypes (AB-NSD-004 and AB-NSD-184) were monitored in branches collected from 20-year-old balsam fir (Abies balsamea L. (Mill.)) trees over a period of 11 months. A significant genotype × harvesting time interaction was observed for endogenous ABA levels and postharvest needle retention duration (NRD). A consistent pattern of seasonal variation in ABA concentration was observed in both genotypes, with the highest amount of ABA (7,887 ng g-1 DW) accumulating in April and May. The highest levels of ABA coincided with the lowest postharvest NRD regardless of genotype. Nevertheless, genotypes differed in their ABA concentrations. Branches of genotype AB-NSD-184 sampled during August exhibited 170 days of NRD whereas those collected in May and June registered the lowest NRD of around 40 days. There was a significant negative correlation (P < 0.05) between endogenous ABA concentrations and postharvest NRD in genotype AB-NSD-184. Also, an inverse relationship was observed between the average daily photoperiod and the postharvest NRD (R 2 = 0.35; P = 0.000) in the same genotype. Together with average daily temperature, the R 2 value for this correlation reached the highest (0.75; P ≤ 0.00). Genotypes differed in their physiological responses to environmental cues and thus differed in their postharvest qualities. Average daily photoperiod and maximum daily temperature are strongly linked to the postharvest NRD through modulating endogenous ABA concentration. © 2013 Her Majesty the Queen in Rights of Canada. Source

Thiagarajan A.,Dalhousie University | Thiagarajan A.,Laval University | Lada R.,Dalhousie University | Pepin S.,Laval University | And 3 more authors.
Trees - Structure and Function | Year: 2012

To fulfill the US Thanksgiving and Christmas tree markets, balsam fir (Abies balsamea (L.) Mill.) is generally harvested before the cold season, anecdotally leading to premature needle senescence. Accordingly, we tested the hypothesis that LT exposure before harvest induces specific hormonal changes and delays postharvest senescence and/or abscission in balsam fir. Two hundred and six seedlings exposed to two temperature treatments for 48 h, LT at 5 °C and controls at 22 °C were severed off roots and monitored for their postharvest needle senescence. Root and shoot (needles and buds) tissues were examined for major endogenous hormone metabolites. LT increased shoot ABA (2,007 ng g -1 DW) by 2.5× and decreased GA 44 (9.84 ng g -1 DW) by 3.5× over those in roots. LT did not alter cytokinins, auxins or any root hormonal concentration. With auxins, only IAA, IAA-Asp, IAA-Leu and IAA-Glu were detected and the concentrations of IAA and IAA-Asp in shoots were lower than those found in roots. Among cytokinins, shoot c-ZR (58.95 ng g -1 DW) and t-ZR (4.17 ng g -1 DW) were 3× higher than those in roots. Apart from GA 44, GA 9 (136.76 ng g -1 DW) was abundant in shoots. The PBL and PNL were 46 and 1.2 %, irrespective of treatments. LT seedlings held needles 11 days longer than the controls (122 days). In balsam fir, short-term LT exposure augmented ABA and decreased GA 44 levels in shoots and delayed postharvest needle senescence. © 2012 Her Majesty the Queen in Right of Canada. Source

Thiagarajan A.,Dalhousie University | Thiagarajan A.,Laval University | Lada R.,Dalhousie University | Pepin S.,Laval University | And 3 more authors.
Scandinavian Journal of Forest Research | Year: 2015

Low temperature (LT) exposure has been shown to delay postharvest needle abscission and senescence (NAS) in balsam fir and changes in vapor pressure deficit (VPD) are expected to alter these processes. Two and half year-old seedlings were exposed to a LT of 5°C for 15 days while the control (CT) group was maintained at 22°C. Seedlings were then exposed to four different VPD (0.22, 0.87, 1.3 and 1.86 kPa) and observed for relative water content (RWC), xylem pressure potential (XPP), membrane injury index (MII), stem capacitance (SC) and NAS. An interactive effect of LT and VPD was observed in RWC, XPP, MII and NAS. Low VPD (0.22 and 0.87 kPa) resulted in less negative XPP, lower electrolyte leakage, higher SC and ultimately higher NAS than those at high VPD. Maximum NAS was recorded at 0.22 kPa. At 1.86 kPa, LT had 5× lower RWC (13%), 3× more negative XPP (−1.1 MPa), 1.8× higher membrane damage and 35% lower NAS (47 days) than CT. The SC declined with an increase in VPD with no effect of LT. The XPP and RWC of LT seedlings showed a positive relationship with NAS with R2 values of 0.54 and 0.59, respectively. LT offered no benefits to NAS at high VPD environments. © 2015 Taylor & Francis Source

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