Response of three Brassica species to high temperature stress during reproductive growth. Can. J. Plant Sci. 80: 693-701. The effect of short periods of high temperature stress on the reproductive development and yield of three Brassica species were studied in a growth chamber experiment conducted for 2 yr. Two genotypes from Brassica juncea L. and one each from B. napus L. and B. rapa L. were grown under day/night temperatures of 20/15°C till early flowering or early pod development, subjected to high temperature stress of 28/15°C or 35/15°C for 7 d and then allowed to recover at 20/15°C. Species differed in optimum temperatures, with B. juncea and B. rapa having higher optimum temperature than B. napus. Dry matter was unaffected by moderate temperature stress, while it was reduced by high temperature stress. The 35/15°C treatment was injurious to reproductive organs at different developmental stages of all three species. High temperatures at flowering affected yield formation more than high temperature at pod development. On the main stem, mean seed yield reduction due to heat stress was 89%, but partial compensation by pods on the branches reduced mean per-plant seed yield decrease to 52%. Reduction in fertile pods (not total pod number), thousand seed weight and seeds per pod were responsible for the reduced seed yield. Brassica rapa was more sensitive to heat stress than B. napus and B. juncea. Although observation did not indicate the exact developmental phase when the reproductive organs were susceptible to heat stress, pods that passed a critical threshold developmental phase tolerated heat stress, which explained the smaller effect of high temperature stress at pod development. A direct temperature effect on reproductive organs appeared to be responsible for the reduction in yield. All genotypes began to recover from the stress by continuing flowering after returning to 20/15°C. Brassica napus was least able to recover from severe stress at flowering, as evidenced by the formation of many abnormal pods during recovery. Per-plant yield response of canola-quality B. juncea line J90-4316 was similar to oriental mustard Cutlass. Thus, heat stress effect depends on the growth stage of canola and mustard and Brassica species differ in heat stress response. napus. La production de matière sèche ne souffrait pas d'un stress thermique modéré (28°C), mais elle était réduite en présence d'un stress élevé (35°C). Chez les 3 espèces, le régime 35°/15°C avait des effets néfastes sur les organes de reproduction à divers stades de leur formation. Des hautes températures à la floraison nuisaient davantage au rendement que quand elles survenaient lors de la formation des siliques. Sur la tige principale, la diminution moyenne de rendement grainier résultant d'un stress thermique était de 89 %, mais pour l'ensemble de la plante, elle n'était que de 52 %, grâce à une compensation partielle opérée par les ramifications. Le manque à produire résultait de la diminution du nombre de siliques fertiles (pas du nombre total de si...

, H. 1998. Physiological responses of plants to salinity: A review. Can. J. Plant Sci. 78: 19-27. Root-zone salinization presents a challenge to plant productivity that is effectively countered by salt-tolerant halophytic plants, but unfortunately, much less successfully by major crop plants. The way in which salt affects plant metabolism is reviewed. Cellular events triggered by salinity, namely salt compartmentation, osmotic adjustment and cell wall hardening are connected to the whole plant responses, namely leaf necrosis, altered phenology and ultimately plant death. The roles of ion exclusion and K/Na discrimination in mediating crop response to salt appear to be central to the tolerance response, but they are by no means essential. The processes involved in regulating ion uptake at the membrane level are considered. Recent work elucidating the interaction between calcium and salinity tolerance is reviewed.Key words: Cell growth, cell turgor, ion regulation, K + /Na + discrimination, osmotic adjustment, salt tolerance Volkmar, K. M., Hu, Y. et Steppuhn, H. 1998. Réponse physiologique des plantes à la salinité: Mise au point bibliographique. Can. J. Plant Sci. 78: 19-27. La salinisation de la rhizosphère est un obstacle à la productivité végétale, qui est exploité avec succès par les plantes halophytes (tolérantes au sel), mais qui est beaucoup plus difficile à surmonter pour les principales espèces cultivées. Les auteurs présentent une mise au point bibliographique des effets des sels sur le métabolisme végétal. Les phénomèmes cellulaires déclenchés par la salinité, notamment la compartimentation des sels, les adaptations osmotiques, le durcissement des parois cellulaires sont reliés aux réactions de la plante, nécrose foliaire, perturbation phénologique et finalement la mort. L'exclusion et la discrimination K/Na dans la médiation des réponses de la plante semblent être au centre des réactions de tolérance, encore qu'elles ne soient en aucun point essentielles. Les auteurs analysent les mécanismes impliqués dans la régulation de l'absorption ionique au niveau membranaire. Ils passent également en revue les travaux récents éclairant l'interaction entre le calcium et la tolérance à la salinité. Mots clés:Croissance cellulaire, turgesgence de la cellule, régulation ionique, discrimination K + /Na + , adaptation osmotique, tolérance au sel A generalized model of plant response to salt stress will be described, relating the whole-plant manifestations of root-zone salinity to initial responses to soil salinity at the cellular level. PRINCIPLESThere is a continuous spectrum of plant tolerance to saline rooting media, ranging from very sensitive glycophytes showing the effects of salt at concentrations of less than 1/10 sea water (50 mol m -3 ), to halophytes, that complete their life cycles at 500 mol m -3 (Flowers et al. 1986; Ungar 1991). The halophyte, Suaeda maritima, for example, exhibits a growth optimum of around 200 mol m -3 and is able to tolerate root zone salinity levels up to 1000 mol m -3 (Clipson et...

. 2008. Adaptation of alternative pulse and oilseed crops to the semiarid Canadian Prairie: Seed yield and water use efficiency. Can. J. Plant Sci. 88: 425Á438. Diversification and intensification of the cropping systems in the traditional wheat-fallow area of the semiarid Canadian prairie is necessary to improve sustainability. Selection of alternate crops to include in cropping systems requires information on production risks with different climate regimes. To understand water use/yield relationships of alternate crops, three pulse crops (leguminous grain crops) [chickpea (Cicer arietinum L.), pea (Pisum sativum L.) and lentil (Lens culinaris Medik.)], three oilseed crops [canola (Brassica napus L. and B. rapa L.) and mustard (B. juncea L.)], and one cereal crop [wheat (Triticum aestivum L.)] were studied under varying water regimes: during 1996Á1998 under well-watered, rainfed, imposed drought conditions, and in 2001 under rainfed conditions. Generally, the relative ranking between crops for water use was maintained across water regimes, such that the crops separated into three general groups of water users (high: wheat, B. napus, mustard; medium: chickpea, B. rapa, lentil; low: pea) with pea using an average of 34 mm and 13 mm less water than high-and medium-water-using crop groups, respectively. The exceptions included desi chickpea, which tended to use less water and B. rapa, which tended to use more water relative to the other crops as water use decreased. Generally, pea and wheat produced the most grain and biomass, had the highest water use efficiency, and had moderately high to high harvest indices. Wheat and pea are well adapted to variable rainfall amounts inherent in semiarid climates. Desi chickpea and lentil produce good grain yields under dry conditions, and grain yields relative to those of other crops can be increased by some drought stress, especially mid-to lateseason stress. Therefore, because of their relatively good performance under water-stressed conditions, they are also well adapted to semiarid climates. Conversely, the Brassica oilseeds yielded relatively poorly compared with wheat and pulse crops under severe water-stressed conditions, so they are not as well adapted to the semiarid climate. In 2001, grain yield of wheat and pulses seeded on stubble was ]30% of the yield on fallow, whereas stubble-seeded Brassica oilseeds yielded only about 10% of that on fallow. Compared with stubble seeding, production of Brassica oilseeds on fallow will decrease the risk of very low yields under drought. We found little indication that mustard was more drought tolerant than B. napus.

can reduce losses by decreasing summer fallow frequency, reverting to hay crops, or growing a more salt-Farmers have requested comparative information on the salt tolertolerant grain crop such as barley (Brown et al., 1982).ance of the field crops they seek to grow as alternatives to wheat. In response, a study was conducted in the Salt Tolerance TestingIn the past, producers commonly aimed to eventually Laboratory at Swift Current, SK, to compare the productivity of canola return to producing wheat following any of these reme-(Brassica napus cv. Cyclone), field pea (Pisum sativum cv. green-seed dial practices. Radley and cv. yellow-seed Carneval), and pinto dry bean (Phaseolus Recently, thin cost-return margins for wheat crops vulgaris cv. Othello) crops to that of a durum wheat (Triticum turhave forced many growers to consider producing green gidum cv. Kyle) crop grown in saline media. Test solutions were or yellow pea, dry bean, canola (Brassica spp.), and salinized prior to seeding by adding NaCl and CaCl 2 (1:1 by mass) to other crops as alternatives to wheat or growing them hydroponic nutrients, resulting in three levels of root-zone salinity: in rotation with wheat. Growers of these alternative near zero, moderate, and severe [solution electrical conductivities of crops have asked for better information pertaining to 1.2 (nutrients only), 11.2, and 24.9 dS m Ϫ1 , respectively]. Eight resalt tolerance. They seek to directly compare inherent sponse variables evaluated crop performance: time from seeding to initial emergence, emergence rate, final emergence and survival, plant tolerances to root-zone salinity among wheat crops and height, aboveground biomass, grain yield, relative grain yield, and their alternatives. grain yield per plant. The durum wheat emerged and survived moder-Results from crop salt tolerance tests conducted ate and severe salinity better than any of the alternative crops. The worldwide between 1950 and 1975 were reviewed by wheat crop also produced more biomass and grain under moderately Maas and Hoffman (1977). These reviewers rated irsaline conditions than produced by the pea and the bean crops, but rigated wheat crops as moderately tolerant. Francois not the canola. Under severe salinity, neither the field peas nor the et al. (1986) field-tested a semidwarf bread wheat crop dry bean produced any grain, but the wheat and the canola crops (T. aestivum cv. Probred) and that from two durum managed to yield 0.4 and 20.1% of their respective productivity in wheats (T. turgidum cv. 1000D & Aldura) grown in nonsaline rooting media. The combined salt tolerance ranking in asan irrigated silty clay soil. On the basis of salinization cending order for the crop cultivars grown in both saline rooting media was: Othello ϭ Carneval Ͻ Radley Ͻ Kyle Ͻ Cyclone.

. Unsaturated hydraulic conductivity of conventional and conservation tillage soils in southern Alberta. Can. J. Soil Sci. 78: 643-648. Conservation tillage is increasing on the Canadian prairies and its long-term effect on soil physical properties warrants investigation. Tension infiltrometer measurements were conducted on conventional tillage (CT), minimum tillage (MT) and no-till (NT) loam to clay loam soils in southern Alberta to determine if 26 yr of conservation tillage (MT, NT) modified the unsaturated hydraulic conductivity, K(ψ), relative to CT. Tillage of CT and MT plots was performed using a wide-blade cultivator. Measurements were performed on tillage treatments that were replicated on two adjacent parcels of land, with readings taken at the west parcel (Site 1) in 1993 and at the east parcel (Site 2) in 1994. Infiltration rates were determined at water potentials (ψ) of -0.3, -0.6 and -1.5 kPa. The K(ψ) values at -0.3, -0.6, -1.0 and -1.5 kPa (equivalent circular pore diameters of 1000, 500, 300 and 200 µm, respectively) were estimated from infiltration data using the nonlinear regression method of Logsdon and Jaynes. Tillage had a significant (P < 0.10) effect on K(ψ). Geometric mean K(ψ) values for NT (12.8 × 10 -8 m s -1 ) were significantly (P < 0.05) lower than for CT (21.9 × 10 -8 m s -1 ), but there was no significant difference between MT (13.6 × 10 -8 m s -1 ) and CT, or between MT and NT. Although there was no significant tillage × site-year interaction (P > 0.10) for K(ψ), there was a trend for higher K(ψ) values at -0.6, -1.0 and -1.5 kPa in CT than MT and NT for Site 1 in 1993 compared to Site 2 in 1994. This trend was consistent with a shorter lag time between the most recent tillage event and subsequent infiltration measurements in CT for Site 1 in 1993 (1-16 d) compared with Site 2 in 1994 (28-45 d).Key words: Tillage, tension infiltrometer, unsaturated hydraulic conductivity Miller, J. J., Sweetland, N. J., Larney, F. J. et Volkmar, K. M. 1998. Conductivité hydraulique à non-saturation des sols selon le régime de travail du sol : classique ou de conservation, dans le sud de l'Alberta. Can. J. Soil Sci. 78: 643-648. La popularité croissante de la pratique du travail de conservation du sol dans la Prairie canadienne justifie qu'on s'arrête à examiner ses effets à terme sur les propriétés physiques du sol. Des mesures par infiltromètre à tension ont été prises sur divers sols allant du loam simple au loam argileux, conduits en travail du sol classique (TC) minimum (TM) et en semis direct (SD) pour déterminer si 26 années de travail de conservation, TM et SD, avaient modifié la conductivité hydraulique à non-saturation (Kψ) par rapport à TC. L'expérience était réalisée dans le sud de l'Alberta. Le travail du sol était effectué au cultivateur à lames larges. Les mesures étaient prises sur des traitements de travail du sol répétés sur deux parcelles de terrain attenantes, c'est-à-dire la parcelle occidentale (emplacement 1) en 1993 et la parcelle orientale (emplacement 2) en 1994. Les tau...