Regulation of cold hardiness in seedlings of western red cedar, yellow cedar and white spruce
Notice bibliographique
Résumé
The development and nature of cold hardiness was examined in first-year seedlings of the three conifer species: western red cedar (Thuja plicata Donn) from southern Vancouver Island, yellow cedar (Chamaecyparis nootkatensis (D. Don) Spach) from northern Vancouver Island and white spruce (Picea glauCa (Moench) Voss) from northern interior of British Columbia. The relationship between free thiols and the development of cold hardiness, and the effects of mefluidide on the induction of hardiness in the three species were also examined. To permit an accurate estimation of cold hardiness, a reliable method of determining hardiness based on the electrolyte conductivity method (EC) was developed for the three species. Optimization of tissue preparation resulted in accurate and reliable estimates of cold hardiness in the three coniferous species. A comparison of visual assessment of shoot damage with the results obtained by the EC method indicated that the two methods were highly correlated although the EC method slightly overestimated the temperature at which 50% of the samples were killed (LT₅₀). The absolute lethal temperature (LT₁₀₀) estimated by the EC method was lower (3 to 7 °C) than that determined by the visual method. The development of hardiness in the three species was characterized by different mechanisms: in white spruce it was initiated by short photoperiod, in red and yellow cedar it was basically regulated by low temperature. Low temperature (7/3 °C day/night) increased hardiness in all three species but subfreezing temperature (2/-3 °C day/night) increased the rate of hardening only in the two cedars. Furthermore, white spruce seedlings were apparently able to attain extreme levels of hardiness (below -65 °C) without exposure to temperatures below 0 °C. The ability to deharden in white spruce was related to the satisfaction of chilling requirements while red and yellow cedar seedlings appeared to deharden only in response to warm temperatures. Mefluidide (0.1 and 0.4 mg l⁻¹ ) applied as a root drench did not increase cold hardiness in any of the three species. Stomatal conductance was however decreased, thus resulting in increased shoot water potentials. Net photosynthesis was reduced predominantly due to stomatal limitations. Mefluidide increased synthesis of ABA in shoots of seedlings of the three species. The level of tissue ABA, like the other variables, was dependent on mefluidide concentration. Low temperature (7/3 °C day and night, 9 h photoperiod, 250 μmoles m⁻² s⁻¹, 400 - 700 nm) induced an increase in free thiols (predominantly reduced glutathione) which was accompanied by an increase in hardiness. Although short photoperiod at a warm temperature (9 h, 20/15 °C day and night) increased hardiness in seedlings of white spruce, no significant increase in thiols was observed. Root application of buthionone sulfoximine and dichlormid affected tissue glutathione levels but these changes did not result in significant changes in freezing resistance. There appears to be no relationship between glutathione and freezing resistance.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».