Aksouh-Harradj, N. M., Campbell, L. C. and Mailer, R. J. 2006. Canola response to high and moderately high temperature stresses during seed maturation. Can. J. Plant Sci. 86: 967-980. Canola is a valuable oilseed crop worldwide. Temperature during the post-anthesis period plays an important role in determining the final yield and seed composition. Experiments were conducted in climate-controlled growth cabinets to test the effect of two high temperature regimes following a 24-h acclimation period on three canola cultivars differing in their thermotolerance. A long, moderately high temperature treatment of 28°C/23°C (day/night) was applied for 10 d from 20 to 30 d after flowering (DAF) and a short, very high temperature regime of 28°C/23°C (day/night) including a peak of 38°C reached for 5 h around midday for 5 d from 25 to 29 DAF. Very high temperature for 5 d reduced yield on the main stem by up to 52% for a sensitive cultivar by reducing seed weight. This treatment also decreased the oil/protein ratio, but had a lesser effect on fatty acid composition. The moderately high temperature treatment for 10 d had only affected yield of one cultivar and increased the oil/protein ratio of all cultivars. However, it had a more pronounced effect on the fatty acid profile. A short period of very high temperature at a sensitive stage can be as critical to canola as mild temperature stress over a longer period.Key words: Brassica napus, oil, protein, fatty acids, tolerance, acclimation, heat stress Aksouh-Harradj, N. M., Campbell, L. C. and Mailer, R. J. 2006. L'effet de deux types de stress thermiques sur le canola pendant la période de reproduction. Can. J. Plant Sci. 86: 967-980. Le colza est une espèce importante de graine oléagineuse dans le monde. Cependant, la température pendant la période de reproduction joue un rôle important dans la détermination du rendement grainier et de la composition finale de la graine. Des expériences ont été entreprises dans des phytotrons pour examiner l'effet de deux types de stress thermiques suivant une journee d'acclimatation sur trois variétes de canola différant dans leur potentiel de tolérance à la chaleur. Un long régime modéré de 28°C/23°C (jour/nuit) a était appliqué pendant 10 jours (de 20 à 30 jours après la fleuraison) et un autre régime brèf a haute température de 28°C/23°C, jour/nuit comprenant une pic de 38°C atteint pendant 5 heures au milieu de la journée pendant 5 jours (de 25 à 29 jours après la fleuraison). La réaction des cultivars a différé selon les deux traitements. Le traitement élevé pendant 5 jours a réduit le rendement sur la tige principale de 52% pour le cultivar sensible en diminuant le poids des grains. Ce traitement a également diminué le rapport huile/proteins, par contre a eu peu d'effet sur la composition d'acides gras. Le traitement modéré pendant 10 jours d'autre part, a eu moins d'effet sur le rendement grainier, a accru le rapport d'huile/proteins, mais a eu cependant un effet plus prononcé sur la proportion d'acides gras. Une période courte de h...
Abbreviations: Abs t , spectrophotometric absorbance at 530 nm at a specifi c water bath temperature ( t ); ETR, electron transport rate; PAR, photosynthetic active radiation; PC, principal component; REC t , relative electrical conductivity at a specifi c water bath temperature ( t ); REML, restricted maximum likelihood; T 50 , temperature (°C) at which 50% relative electrical conductivity occurred; TTC, 2,3,5-triphenyltetrazolium chloride.
We demonstrate the use of nanofabricated capillaries, integrated as part of a microfluidic structure, to study the electrophoretic behaviour of single, fluorescently-labelled, molecules of DNA as a function of capillary size. The nanocapillaries, fabricated using a focused ion beam, have cross-sections down to 150 x 180 nm. Control of single-molecule direction and velocity was achieved using voltage manipulation. DNA mobility was found to increase with decreasing cross-section, which we interpret in terms of reduced electro-osmotic counter-flow. Such nanofabricated capillaries as part of larger fluidic structures have great potential for biotechnology, particularly single molecule manipulation and analysis.
Increasing plant P supply has been shown to either increase or decrease the salt tolerance of many plants. Tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse in a continuously flowing solution culture system to investigate whether P fertilization modified the detrimental effects of NaCl at low constant P concentrations similar to those in soil solutions. Increasing P fertilization enhanced the tolerance of tomato plants to NaCl. At 0.1, 1.0, and 10 mM P, the NaCl concentrations that reduced yields of fruit by 50% were 58,72, and 130 mM, respectively. Salinity reduced foliar P concentrations. This may have been mediated partly through ionic strength effects, which decreased the activity of H2PO4−1 by about 40%. Plants grown under saline conditions had higher internal P requirements. When the NaCl concentration was increased from 10 to 50 and 100 mM, the corresponding concentrations of P in the youngest mature leaf required to obtain 50% yield were increased from 1.8 to 2.4 and 3.0 g kg−1. The change in internal P requirement was also evident by the relative severity of foliar symptoms of P deficiency in plants growing in the saline treatments at any given foliar P concentration. Adequate P nutrition was essential for effective ionic compartmentation. Under saline conditions, increasing the solution P concentration from 1.0 to 10 μM decreased Na and increased K concentrations in immature leaves but increased Na and decreased K in the mature leaves. Accumulation of ions for osmotic adjustment and restriction of Na and Cl accumulation in immature leaves appear to be involved in P enhancement of salt tolerance of tomato plants.
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