Bibliographic record
Abstract
Although Cannabis sativa L. has been grown for millennia as a multipurpose crop, little is known about its freezing tolerance and capacity to cold acclimate. Plants native to temperate regions are able to increase their cold hardiness when exposed to low temperatures through a process called cold acclimation. These organisms developed different strategies to deal with cold, and may involve alterations of the photosynthesis apparatus, the accumulation of carbohydrates and the production of protective molecules. Such strategies often start with the induction of cold-regulated genes (COR genes) notably via changes in chromatin structure. This thesis focuses on the cold acclimation capacity and freezing tolerance of hemp and uncovers underlying epigenetic and molecular mechanisms. The first objective consisted in ranking nine Cannabis sativa L. varieties approved for production in Canada according to their cold acclimation capacity and freezing tolerance. A whole-plant freezing test revealed a range of phenotypic variations for these traits, which enabled us to classify nine Cannabis sativa L. varieties into three groups. The first group holds varieties that acclimate the most efficiently, the second group includes varieties with modest cold acclimation capacities while the third group comprises sensitive varieties that do not acclimate. However, further analysis indicated that all varieties displayed similar cold-response strategies regarding photosynthesis and the accumulation of soluble sugars. In the second objective, we identified COR genes in the genome of Cannabis sativa L. and by monitoring their expression levels, we uncovered that all varieties could induce the expression of COR genes in response to cold. However, the varieties that could cold acclimate the most efficiently accumulated COR transcripts to higher levels. In the third objective, we observed that all varieties modified their epigenome in response to cold with however a distinction that the most successful varieties displayed more pronounced global DNA methylation dynamics and a wider range of variations of cytosine methylation and histone modifications at COR gene loci. Altogether, this study is the first to report the cold acclimation and freezing tolerance capacities of Cannabis sativa L. characterised at the physiological, metabolic and molecular levels. Findings from this study may serve as stepping-stones for the sustainable development of Cannabis culture in Canada and other northern countries.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".