Thaw effects on cold-hardiness parameters in yellow birch
Notice bibliographique
Résumé
One-year-old, cold-hardened, container-grown yellow birch (Betula alleghaniensis Britt.) seedlings were exposed to cold treatments after being pretreated with a simulated winter thaw. Freezing injury to roots and shoots was assessed by relative electrolyte leakage and triphenyltetrazolium chloride reduction. Growth characteristics were also determined after 60 days under greenhouse conditions. Relative electrolyte leakage and triphenyltetrazolium chloride reduction measurements showed that roots became increasingly damaged with decreasing cold-treatment temperatures. However, plants pretreated with thaws showed significantly lower stem increment, shoot length, and leaf area in response to the cold temperatures than did the unthawed plants. Variation in these growth parameters was also significantly correlated with both root and shoot freezing injury parameters. Cold hardiness under different thaw pretreatments was assessed using the highest freezing temperature that caused significant injury, referred to as the critical temperature. For seedlings without the thaw pretreatment, shoot and root critical temperatures were estimated as 52.5 and 23.8°C, respectively. Following 12 days of thaw, these temperatures increased to 24.08°C for shoots and 13°C for roots. Twelve days of thaw, or growing degree-day (>4°C) accumulations greater than 66 during a thaw, could sufficiently deharden roots and shoots such that they would be susceptible to freezing damage at ambient temperatures commonly encountered in the Canadian Maritimes. We also observed that root pressure declined significantly with increasing root freezing injury. Sufficient root pressure is required for springtime refilling of xylem embolisms caused by winter cavitation of the vessels in this species. Weak root pressure caused by freezing injury would represent a risk of shoot dieback and tree decline due to the remaining embolisms reducing water flow to the developing foliage. The rapid reduction of shoot cold hardiness may also indicate the threat of late-spring frosts to this species. These induced changes are especially important under climate change scenarios that suggest increases in winter temperatures and changes in seasonality in eastern Canada.Key words: climate change, cold hardiness, electrolyte leakage, growth, root pressure, TTC reduction.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| 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 tête enseignante, 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 ».