#Douglas fir seedlings plus#

Based on the data obtained, the freezing tolerance of pomegranate correlated well with some tree and fruit characteristics, such as chilling for the start of bud break (r = 0.63), seed toughness (r = −0.63), and pH of fruit juice (r = 0.38). The results showed large differences in freezing tolerance (−15.33 ☌ to −24.36 ☌) among the studied pomegranate cultivars and can be classified as cold sensitive (−15.33 ☌ to −18.66 ☌), intermediate (−19.23 ☌ to −22 ☌), and winter hardy (−22.56 ☌ to −24.36 ☌). Freezing tolerance was measured using the LT50 (the lethal temperature at which 50% of electrolytic leakage occurs and 50% of tissue dies) method. The goal of this study was not only to assess the freezing tolerance of 20 pomegranate varieties from various parts of Iran but also to look into a possible link between freezing tolerance and tree and fruit traits, as well as geographic and meteorologic factors. Les résultats sont discutés dans la perspective des effets d'un réchauffement du Globe.įreezing injury is one of the most critical climatic factors impacting pomegranate development and productivity.

#Douglas fir seedlings plus#

Quelle que soit l'origine des graines, la réponse à la croissance est d'autant meilleure que la phase d'élimination de dormance est plus longue (tableau I) et plus froide (tableau II). Ensuite, après une mise en végétation à 15☌ pendant 9 semaines, on a individuellement noté le degré de débourrement des plants et déterminé le poids sec des nouvelles pousses formées. A partir de mi-octobre ils ont été soumis à une température constante de 5, 7 ou 9 ☌ pendant des durées de 9, 11, 13 ou 15 semaines, en vue de lever leur dormance. Ils provenaient de sites côtiers chauds ou montagneux frais de l'Orégon. Des semis de 2 ans de sapins de Douglas ont été transférés en conteneurs, puis placés en conditions naturelles pendant une saison de végétation. Réchauffement du Globe et besoin en froid du douglas. Results are discussed with reference to predicted global warming. The longest and coldest chilling treatment produced the greatest growth response for all seed sources. After a growth period of 9 wk following chilling, the degree of bud break and the weight of new shoot growth were recorded. Potted Douglas-fir seedlings from warm coastal and cool mountainous Oregon seed sources, grown under natural conditions, were chilled at constant temperatures of 5, 7, or 9° C for periods of 9, 11, 13 or 15 wk beginning in mid-October. Of dormancy and cold hardiness development in Douglas-fir growing in the relatively mild temperate region of western Oregon, We conclude that climatic warming will influence the physiological processes Terminal buds and reduced growth of the leader shoot.

Exposure to elevated temperature reduced final % bud burst of both leader and branch Within a shorter period in trees at ambient temperature (with and without elevated CO2) than in trees at elevated temperature. Time of bud burst was more synchronous and bud burst was completed Treatments than in the ambient temperature treatments. After bud burst started, however, the rate of increase in % bud burst was slower in the elevated temperature For trees in the elevated temperature treatments, date to 30% burst of branch terminal buds was advanced by about 6 andġ5 days in the presence of elevated CO2 and ambient CO2, respectively. In general, trees exposed to elevated CO2 were slightly less hardy during hardening and dehardening than trees exposed to ambient CO2. At maximum hardiness, trees in the elevated temperature treatment were less hardy by about 7 ☌ than trees in theĪmbient temperature treatment. The elevated temperature treatment delayed needle cold hardening in the autumn and slowed dehardening in the Or elevated (ambient + ∼ 4 ☌) air temperature in the presence of an ambient or elevated (ambient + ∼ 200 ppm) CO2 concentration. Two-year-old seedlings were grown for 2.5 years in semi-closed, sunlit chambers at either ambient

We examined effects of elevated CO2 and temperature on cold hardiness and bud burst of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings.