The basics, explained simply

Short explanations of the technical terms that show up in the lexicon articles. Each entry answers one question: what does this word mean, without the jargon? If a longer article leaves you stuck on a term, the plain version is here.

  • Genetics and Breeding

  • Genome and Inheritance

  • B-Locus

    What the B-Locus is, how the codominant BT and BD alleles fix the THC-CBD chemotype, why F2 offspring split 1:2:1, and where the single-locus model reaches its limits.

  • Cytoplasmic Inheritance

    What cytoplasmic inheritance is, why chloroplasts and mitochondria pass through the mother only in most plants, how that pollen exclusion works, and where the rule breaks down.

  • Heterozygosity

    Heterozygosity means a plant carries two different variants at one place in its genome, and in cannabis that is the normal state rather than the exception.

  • Homozygosity

    Homozygosity means a plant carries the same variant twice at one place in its genome, and it is the condition under which a cross always yields the same progeny.

  • Maternal Inheritance

    What maternal inheritance means, how it shows up in reciprocal crosses, why in cannabis it concerns the organelle genes, and why aroma still comes from both parents.

  • QTL

    What a quantitative trait locus is, why continuous traits like terpene content or plant height depend on several loci, and how QTL mapping locates them in the genome.

  • Recombination

    Recombination is the rearrangement of alleles during the formation of gametes, and in some stretches of the genome it happens so rarely that linked traits stay together.

  • XY-System

    What the XY system means in cannabis, why females carry XX and males XY, why the Y holds almost no active genes, and why the sex-determining gene is thought to sit on the X.

  • Crossing and Breeding

  • Backcross

    A backcross recovers one parent's genome step by step while keeping a single trait from the other line, and its reach depends on two conditions.

  • Double Cross

    In a double cross, four true-breeding lines are joined first in pairs and then across, so that commercial seed grows on a vigorous cross rather than on a weakened line.

  • Filial Generation

    Filial generations count the daughter generations of a cross, and only the second of them reveals which trait combinations can actually be selected.

  • Heterosis

    Heterosis is the gap between an offspring and the average of its two parents, and measured on a single cross that number is hard to read.

  • Inbreeding Depression

    What inbreeding depression is, how rising homozygosity exposes recessive harmful alleles, why vigour and yield decline, and what purging means in breeding.

  • Linkage Drag

    Moving a single gene from an outside line into a variety always brings a piece of chromosome with it, and how large that piece stays is decided not by the number of crosses but by the position in the genome.

  • Reciprocal Cross

    What a reciprocal cross is, how swapping the parent roles reveals whether a trait sits in the nucleus or with the mother, and what the test showed for cannabis aroma.

  • Selfing

    What selfing is, why both halves of the genome come from one plant, how recessive traits surface, and why continued selfing leads into inbreeding depression.

  • Sex Reversion

    In sex reversion a genetically female plant forms fertile male flowers, or a male plant fertile female ones, triggered through the ethylene pathway, and both feminised seed and selfing rest on it.

  • Single Seed Descent

    In single seed descent exactly one seed from each plant carries the next generation, and in cannabis the method reaches functionally true-breeding lines in about six rounds.

  • Transgression

    Transgression describes offspring whose trait values fall outside the range of both parents, and in the case measured it arose from similar parents rather than distant ones.

  • Plant and Seed

  • Botany and Development

  • Adventitious Root

    What an adventitious root is, which tissues it can arise from, and why propagation from cuttings would be impossible without it.

  • Anthesis

    What anthesis means, why it is not the same as switching the lights, and how that difference can make two statements about harvest timing impossible to compare.

  • Rhizosphere

    What the rhizosphere is, why breakdown processes occur there that do not occur in bulk soil, and how that differs from removing a substance with the harvest.

  • Seeds and Germination

  • Dormancy

    What dormancy means, why South African landraces respond to dormancy breakers and industrial hemp does not, and what cold stratification actually achieves.

  • Equilibrium Moisture Content

    Equilibrium moisture content is the level at which a seed is in balance with the air, and it depends on humidity, oil and temperature.

  • Germination Capacity

    Germination capacity is a count made under defined conditions, and those conditions belong to every percentage figure quoted.

  • Germination Energy

    Germination energy records only the well-developed seedlings at day three and therefore says something about a lot's speed rather than its yield.

  • Normal Seedling

    Whether a seedling counts as normal decides every germination figure, and the call rests on root and shoot rather than on the hull splitting open.

  • Seed Dormancy

    Seed dormancy means a seed is alive and still does not germinate; in freshly harvested hemp it lasted five to six weeks in one study and made germination tests come out worse than the seed really was.

  • Seed Moisture Content

    Seed moisture content refers to fresh weight, is determined in a drying oven and steers drying through a target weight.

  • Seed Vigour

    Seed vigour describes performance under adverse conditions, and for hemp the major testing bodies carried no procedure for it in 2019.

  • Sorption Isotherm

    A sorption isotherm assigns a seed's moisture content to each humidity, and for hemp it has been measured down to about 20 % humidity.

  • Viability

    Viability is determined by staining a cut seed and answers in two days what a germination test only settles after a week.

  • Chemistry and Processing

  • Biochemistry and Metabolism

  • Cannabigerolic acid

    What cannabigerolic acid is, why the plant makes it rather than its neutral form, and why the difference between CBGA and CBG decides how a lab result should be read.

  • Cannabinoid synthase

    What a cannabinoid synthase does, why THCA and CBDA synthase resemble each other so closely, and why the switch between THC and CBD separates less cleanly in the lab than in the textbook diagram.

  • Chelate

    What a chelate is, why iron in fertiliser comes as a chelate, and which iron chelate you need at which pH.

  • Chemotype

    What a chemotype is, how Small and Beckstead defined types I to III by the THC-CBD ratio in 1973, what the rarer types IV and V mean, and why chemotype says more than indica or sativa.

  • Dilution effect

    A higher THC percentage with a smaller harvest can simply mean that the same amount of compound sits in less flower mass.

  • Terpene Synthase

    What a terpene synthase is, how it builds the scent compounds of cannabis from GPP and FPP, why one enzyme often makes several terpenes, and what that means for breeding terpene profiles.

  • Tetrahydrocannabinolic acid (THCA)

    What THCA is, why the plant builds almost nothing but the acid form, and why the conversion factor of 0.877 describes an upper limit rather than a yield achieved.

  • Processing

  • Lecithin

    What lecithin does as an emulsifier, what is established about bioavailability, and how bound residual water affects shelf life.

  • Maceration

    What maceration means, what the yield depends on, and how it differs from decarboxylation.

  • Soil and Substrate

  • Bioaccumulation factor

    The bioaccumulation factor compares how much of a substance sits in the plant against how much sits in the soil, and a high value alone does not make a good remediation crop.

  • Cation Exchange Capacity

    What a substrate's cation exchange capacity means, why it makes coco change the nutrient solution while rockwool does not, and what that means in practice.

  • Phytoextraction

    In phytoextraction a plant takes up a contaminant and carries it off the site with the harvest, and whether that is enough is decided by the mass hauled away, not by the idea.

  • Phytostabilisation

    How phytostabilisation differs from phytoextraction, how roots and their exudates bind a substance, and why the effect has not been studied for cannabis specifically.

  • PourThru

    How to use the PourThru to measure pH and EC at the root without taking the plant out of its pot, and what to watch so that readings stay comparable.

  • Transfer factor

    What the transfer factor stands for, why a low value means clean produce and an ineffective clean-up at the same time, and why German soil law lacks trigger values because of it.