Bélanger, G., Castonguay, Y. and Lajeunesse, J. 2014. Benefits of mixing timothy with alfalfa for forage yield, nutritive value, and weed suppression in northern environments. Can. J. Plant Sci. 94: 51–60. Alfalfa can be grown alone or with a grass, but little information exists on the benefits of mixing alfalfa (Medicago sativa L.) with a grass in northern environments. Our objectives were (1) to determine the benefits in terms of forage yield, nutritive value, and weed suppression of mixing timothy (Phleum pratense L.) with alfalfa and (2) to evaluate the persistence of alfalfa cultivars of varied adaptation to cold and of alfalfa populations selectively improved for superior freezing tolerance in a grass–legume mixture and in monoculture. This study was conducted in a region with 1700 degree-days (5°C basis) with one harvest in the seeding year (2008), three harvests in each of two post-seeding years, and one harvest in the third post-seeding year. Adding timothy to alfalfa increased the seasonal total dry matter (DM) yield by an average of 0.57 Mg DM ha−1 yr−1 in the first 2 post-seeding years and this seasonal effect was due mostly to a DM yield increase at the first harvest. The weed contribution to total DM yield in the three harvests of the first 2 post-seeding years was greater in the alfalfa monoculture (16 to 47%) than in the alfalfa–timothy mixture (12 to 36%). Mixing timothy with alfalfa also increased neutral detergent fibre concentration and digestibility, decreased N concentration, and tended to increase water soluble concentration, but had little effect on forage DM digestibility. Cultivars and populations recurrently selected for superior freezing tolerance did not differ in persistence and had a limited effect on DM yield and nutritive value attributes. The positive effect on DM yield of mixing timothy with alfalfa was not accompanied by a reduction in forage digestibility that is usually observed with increased DM yield.

Morin, C., Bélanger, G., Tremblay, G. F., Bertrand, A., Castonguay, Y., Drapeau, R., Michaud, R., Berthiaume, R. and Allard, G. 2012. Short Communication: Diurnal variations of nonstructural carbohydrates and nutritive value in timothy. Can. J. Plant Sci. 92: 883–887. Nonstructural carbohydrate (NSC) concentration in timothy (Phleum pratense L.) increased during the day by 16 to 41 g kg−1 DM (+23 to 137%) in spring and summer growth cycles and reached a maximum value between 12.8 and 13.2 h after sunrise in an area with 15 to 16 h of day length. This increase in NSC concentration was generally accompanied by a decrease in concentrations of neutral detergent fiber (−2 to 6%), acid detergent fiber (−1 to 7%), and N (−6 to 11%).

The present study documents the changes in carbon and nitrogen metabolites occurring in apical buds and previous year stems of white spruce seedlings (Picea glauca [Moench] Voss) with contrasting growth phenotypes (tall vs. small) after transfer to short day (SD; 8 h) photoperiod to induce bud formation. Concentrations of total nonstructural carbohydrates markedly increased in the developing buds within the days after transfer to SD, mainly as a result of increased concentrations of monosaccharides such as glucose, fructose, and pinitol. At the same time, starch levels declined, with the resulting carbohydrates presumably used to meet early carbon requirements of the SD-induced apical bud. Concentrations of glutamine, glutamic acid and proline also decreased immediately after transfer to SD in both organs. Later stages of SDinduced bud formation were characterized by an increase in starch, sucrose, and glutamine concentrations in previous year stems, concomitant with an increase in the steady-state levels of UDP-glucose pyrophosphorylase and glutamine synthetase protein. In contrast, arginine levels increased after 2 weeks of SD exposure, indicating a transition in arginine metabolism at the time of initiation of shoot stem primordia and bud elongation. Higher accumulation of total nonstructural carbohydrates and total amino acids in previous year stems of small trees could indicate lower sink strength of apical bud during its development, which could in turn impact subsequent tree growth.Résumé : La présente étude présente les changements se produisant au niveau des métabolites carbonés et azotés dans le bourgeon terminal et la tige de l'année précédente d'épinettes blanches (Picea glauca [Moench] Voss) ayant des phénotypes de croissance contrastés (petits versus grands arbres), après avoir été transférées en conditions de jours courts (JC ; 8 heures) de manière à induire la formation des bourgeons. Les concentrations en hydrates de carbone non structuraux augmentent de manière marquée dans les bourgeons en développement immédiatement après le transfert en JC, principalement en raison de l'augmentation des concentrations en monosaccharides tels que le glucose, le fructose et le pinitol. Au même moment, les niveaux d'amidon diminuent en faveur de l'augmentation des sucres solubles indispensables à la demande en carbone reliée à formation des bourgeons terminaux induite en JC. Les concentrations en glutamine, acide glutamique et proline diminuent également immédiatement après le transfert des épinettes en JC dans les deux organes. Les stades plus avancés de la formation des bourgeons terminaux induite en JC sont caractérisés par une augmentation des concentrations en amidon, en saccharose et en glutamine dans les tiges de l'année précédente, en concomitance avec une augmentation des niveaux d'UDPglucose pyrophosphorylase et de glutamine synthase. En revanche, les concentrations en arginine augmentent après 2 semaines d'exposition aux JC, suggérant qu'une transition au niveau du métabolisme de l'arginine se produit...