Cold Stress and Chilling Injury
Identify how low tissue and root-zone temperatures alter membranes, metabolism, photosynthesis, water transport, and recovery in cannabis.
Educational reference · evidence, sources, and limits shown below
Identify how low tissue and root-zone temperatures alter membranes, metabolism, photosynthesis, water transport, and recovery in cannabis.
Terms to know
- Chilling stress
- Injury or functional suppression caused by low, nonfreezing temperature in a sensitive plant.
- Freezing injury
- Damage associated with extracellular or intracellular ice formation.
- Photoinhibition
- Reduction in photosynthetic capacity when absorbed light exceeds safe processing and repair.
- Cold acclimation
- Physiological adjustment that increases tolerance to subsequent low temperature.
Core science
Cold slows enzyme activity, membrane transport, respiration, root growth, and water movement. Leaves may remain exposed to substantial light while carbon metabolism and repair slow, increasing photoinhibition risk. Chilled roots can restrict uptake even when air conditions appear acceptable.
Membrane lipids, genotype, prior acclimation, tissue age, duration, and rate of cooling influence injury. Symptoms can include slowed growth, drooping, discoloration, marginal injury, delayed rooting, and nutrient-like patterns. These signs are not unique and may appear after the cold event.
Night-time radiation, cold supply air, exterior surfaces, irrigation solution, outdoor transplant shock, and power failures can chill tissues below the room average. Condensation may accompany cooling when surfaces approach the dew point, adding disease risk to physiological stress.
Why this matters in cultivation
- Investigate minimum and duration, not only the daily average. Map cold surfaces and supply-air paths, measure root-zone and leaf temperature, and inspect equipment histories. During recovery, warm gradually and coordinate light so photosynthetic demand does not outrun repair.
- Distinguish chronic cool growth from an acute excursion. Record whether new growth resumes and whether reproductive development, roots, or specific canopy zones remain affected before deciding crop disposition.
Measure and record
Exposure
Minimum air, leaf, and root-zone temperature; duration; cooling and warming rate; and operating state.
Dew risk
RH, dew point, surface temperature, condensation, and wetness duration.
Plant response
Tissue and location, symptom onset, growth rate, water use, and root condition.
Recovery
Warming method, light adjustment, time to restored function, and residual injury.
Cause
Weather, HVAC, door, power, irrigation-temperature, or control-system event and CAPA.
Common misconceptions
Correction: Chilling-sensitive function can decline above freezing.
Correction: Genetics, cold, light, sugar status, and nutrient issues can overlap visually.
Correction: Root-zone temperature and damaged physiology may recover more slowly.
Evidence limits
Cold tolerance differs widely among cannabis germplasm and developmental stages. Use facility-specific alarm limits based on measured crop response, not folklore labels such as indica or sativa.
Related encyclopedia topics
- THC-ENC-065-068, THC-ENC-083, THC-ENC-090, THC-ENC-096, THC-ENC-100, and emergency-response SOPs.
Source notes
- Nobel P.S. (2009). Physicochemical and Environmental Plant Physiology, 4th ed. Academic Press.
- THC Cannabis Plant Science Source Packet v1.1 (project source, May 2026).
- THC Cultivation SOP Source Materials Packet v1.0 (project source, May 2026).
This lesson summarizes the source material and its evidence limits for education. Use direct measurement, controlled comparison, and the cited sources when conditions differ or a decision carries meaningful risk.