Could Cold-Tolerant Hemp Expand Where the Crop Can Grow?

Industrial hemp is often described as a hardy crop, but that label can hide an important reality. Hemp still has biological limits, and low temperatures can interfere with growth long before a plant dies or shows obvious damage above ground.

A 2026 study¹ published in Plant Physiology and Biochemistry examined what happens inside hemp roots during prolonged cold exposure. The researchers found that the roots did more than slow their growth. They reorganized the lipids that form cellular membranes, activated protective enzymes, accumulated stress-related compounds, and changed the activity of thousands of genes.

The findings provide a detailed view of hemp’s molecular response to cold. More importantly, they point toward traits that breeders may eventually use to develop cultivars better suited to northern growing regions, unpredictable spring weather, and other environments where soil temperatures can restrict early plant development.

Why Cold Soil Can Be a Hidden Problem for Hemp

Discussions about cold damage usually focus on leaves, stems, and visible frost injury. Roots receive less attention because they are hidden below the soil. However, they are responsible for absorbing water and nutrients while anchoring the plant and supporting growth above ground.

Cold soil can make those functions more difficult. Low temperatures alter chemical reactions, reduce metabolic activity, and affect the physical properties of cellular membranes. If root membranes become too rigid or damaged, cells may struggle to regulate what enters and exits. Water and nutrient uptake can suffer even when the plant still appears relatively healthy.

This makes root performance an important but easily overlooked part of cold tolerance. A hemp cultivar that protects its leaves but cannot maintain functional roots may still experience slower establishment, reduced biomass, or greater vulnerability to additional stress.

The new study investigated that hidden response using Longdama 9, an industrial hemp cultivar maintained by the Heilongjiang Academy of Agricultural Sciences in China.

How Researchers Tested Hemp Under Cold Stress

The researchers grew hemp seedlings hydroponically under controlled conditions. Once the seedlings had developed four pairs of true leaves, one group was exposed to a temperature of 4°C. Plants maintained under normal growing conditions served as controls.

Samples were collected over seven days. The team measured root growth, membrane damage, antioxidant activity, and the accumulation of compounds that help plants manage cellular stress. They also used lipidomics to identify changes in root lipids and RNA sequencing to determine which genes became more or less active.

This combined approach was important. Measuring growth alone would show that cold harmed the plants, but it would not explain how the roots responded. By combining physical observations with molecular data, the researchers could follow the process from visible growth inhibition down to individual lipid classes and regulatory genes.

Cold Reduced Hemp Root Growth and Damaged Cell Membranes

After seven days at 4°C, the cold-treated hemp seedlings showed clear signs of impaired root development. Root volume fell by 24%, while root fresh weight declined by 28%. Root dry weight also decreased by 25%.

Indicators of cellular damage increased at the same time. Relative electrical conductivity rose 2.9-fold, suggesting that root cell membranes had become more permeable. Malondialdehyde, a commonly measured product of lipid oxidation, increased 3.8-fold.

These results show that the cold treatment was not merely slowing normal development. It was placing enough pressure on the roots to disrupt cellular membranes and trigger a broad defensive response.

Hemp Roots Rebuilt Their Lipid Architecture

Cell membranes are not fixed shells. They are flexible structures made largely from lipids, and plants can alter their composition when environmental conditions change.

Under cold conditions, membranes tend to become more rigid. Plants can compensate by changing the types and proportions of lipids present, helping preserve the flexibility needed for transport, signaling, and normal cellular function.

The hemp roots displayed extensive lipid remodeling. Phosphatidylcholine decreased by 25%, while phosphatidic acid increased by 26%. Digalactosyldiacylglycerol increased by 27%, whereas monogalactosyldiacylglycerol declined by 46%. Triacylglycerol, commonly known as TAG, increased by 69%.

The balance among these lipids may matter as much as the change in any single category. The researchers observed shifts in several lipid ratios, suggesting that the roots were reorganizing membrane structure rather than simply producing more lipids overall.

TAG accumulation is particularly interesting. TAG is a neutral storage lipid rather than a primary structural component of most cellular membranes. Its increase may help cells temporarily store fatty acids released during membrane remodeling, reducing the risk that free fatty acids cause further damage. It may also preserve material that can later be reused if normal conditions return.

Hemp Activated Several Layers of Cold Protection

Lipid remodeling was only one part of the response. The cold-treated roots also accumulated soluble sugars, soluble proteins, and proline. These compounds can help cells maintain water balance, stabilize proteins and membranes, and cope with the disruption caused by environmental stress.

Antioxidant defenses increased as well. Cold stress can lead to the accumulation of reactive oxygen molecules that damage lipids, proteins, and other cellular components. The hemp roots responded by increasing the activity of superoxide dismutase, peroxidase, and catalase.

Together, the observed response involved several connected processes:

• Reorganizing membrane lipids to support cellular stability
• Accumulating compounds that assist with osmotic adjustment
• Increasing antioxidant activity to limit oxidative damage
• Changing gene activity to coordinate the wider response

This is an important insight for breeding. Cold tolerance is unlikely to depend on one defensive mechanism acting alone. A resilient cultivar may need to coordinate membrane maintenance, antioxidant protection, energy management, and continued root function at the same time.

Thousands of Genes Changed Their Activity

RNA sequencing identified 5,786 differentially expressed genes in the cold-treated hemp roots. Of those, 730 were associated with lipid metabolism.

Several genes involved in lipid synthesis, phospholipid degradation, and fatty acid desaturation became more active. Increased fatty acid desaturation can help membranes remain functional at lower temperatures because unsaturated fatty acids generally support greater membrane fluidity.

The researchers also investigated how some of these genes were controlled. They found that a zinc finger transcription factor called CsZincF could bind to the promoter of CsDGAT2 and activate its transcription. CsDGAT2 is involved in the production of TAG, the lipid category that increased markedly during cold exposure.

This proposed CsZincF and CsDGAT2 relationship provides a possible link between cold sensing and lipid storage. Instead of observing only that TAG increased, the researchers identified part of the regulatory machinery that may have helped produce that change.

Cold-Tolerant Hemp Could Be a Breeding Opportunity

The most immediate value of the research lies in the targets it provides for future investigation. If certain genes, lipid profiles, or biochemical responses repeatedly appear in cold-tolerant hemp, breeders may be able to screen plants for those characteristics.

That could eventually make cultivar selection more precise. Traditional breeding often requires plants to be grown, exposed to environmental pressure, and evaluated over time. Molecular indicators could help breeders identify promising candidates earlier, although field performance would still need to be confirmed.

Cold-tolerant cultivars would not make temperature irrelevant. They could, however, improve establishment during cool springs, reduce losses caused by unexpected temperature drops, or make hemp production more dependable in northern regions.

The commercial value would extend beyond total acreage. Greater consistency could benefit processors that depend on predictable supplies of fiber, grain, or other hemp-derived materials. A crop can have valuable end uses and still struggle commercially if regional yields vary too widely or growers consider production too risky.

Why the Findings Are Not Yet Ready for the Field

The study provides a molecular framework, not a finished agricultural solution. Only one hemp cultivar was tested, so it is not yet clear whether the same response occurs across genetically diverse cultivars. The plants were also grown hydroponically in a controlled chamber rather than in soil under field conditions.

The 4°C treatment represented sustained cold exposure. Real fields experience fluctuating temperatures, changing moisture, wind, sunlight, and interactions with microorganisms. The researchers also did not include a recovery period, leaving unanswered questions about whether the altered lipid profile returned to normal or produced lasting effects.

Most importantly, the proposed functions of the key genes have not been confirmed using stable hemp plants in which those genes were disabled or overexpressed. The interactions involving CsZincF and CsDGAT2 were supported through yeast one-hybrid and dual-luciferase assays, but further in-plant validation is required.

The Bigger Lesson From Hemp’s Cold Response

This research reinforces a broader lesson about crop resilience. Environmental tolerance is not simply the ability to survive an extreme event. It is the ability to protect essential functions, allocate resources effectively, and recover without sacrificing too much growth or yield.

For hemp, roots may be central to that calculation. The study shows that cold exposure can trigger membrane damage and reduce root biomass, but it also reveals a coordinated system working to contain that damage. Lipids are reorganized, antioxidants become more active, protective compounds accumulate, and gene expression changes across multiple pathways.

The next step is to determine which of these responses genuinely separate tolerant hemp from sensitive hemp under real agricultural conditions. If researchers can identify reliable markers and validate them across cultivars, cold tolerance could become a measurable breeding objective rather than a vague description attached to certain varieties.

That would move the discovery from molecular biology toward practical agriculture. It could help producers choose cultivars based not only on cannabinoid content, fiber quality, or seed yield, but also on how well the roots maintain function when the growing season begins colder than expected.

References:

^{1. Yan, B., Chang, C., Sui, Y., Zhao, X., Zheng, N., Fang, Y., Zhang, Y., Zhang, M., & Zhang, L. (2026). Transcriptome and lipidome analyses reveal membrane lipid remodeling in root tissues of Cannabis sativa L. exposed to cold stress. Plant Physiology and Biochemistry, 111683. https://doi.org/10.1016/j.plaphy.2026.111683}