Vegetable Program Glossary

This page comprises terms found throughout the Vegetable Program's web pages.

abscisic acid (ABA)
A plant hormone, C15H20O4, involved in the abscission (shedding) of leaves, flowers, and fruits and the dormancy of buds and seeds. Can cause fruit ripening and has effects on plant water use and moisture retention.
See Transplant Performance pages
See abscission layer below

abscission layer
A layer of cells that forms at the base of a fruit or leaf stalk where it is attached to the stem. The veins that carry nutrients and water into and out of the structure become closed off, and the fruit or leaf will eventually fall off.
See full slip and half slip

acetic acid (vinegar)
A clear, colorless organic acid, CH3COOH, with a distinctive pungent odor, used as a solvent and in the manufacture of rubber, plastics, acetate fibers, pharmaceuticals, and photographic chemicals. It is the chief acid of vinegar.

agronomy
A branch of agriculture dealing with field-crop production and soil management; application of the various soil and plant sciences to soil management and crop production

alternate host
A secondary host plant that

becomes infected and is necessary for alternating generations of a disease-causing organism

anther
The male reproductive organs found within a flower, where pollen is produced.

aromatic
Having an aroma; fragrant or sweet-smelling.
See aromatic herb

aromatic herb
An aromatic plant or substance, such as a medication.

aster yellows
A widespread disease of plants caused by a mycoplasma, usually resulting in stunted growth and yellowing of infected individuals. (picture) (picture 2)
See mycoplasma

augmented supersweet corn (shq)
In this newly developed type of corn, every kernel has the sh2 gene resulting in a high sugar content and slow conversion of these sugars to starch. However, some of the kernels also have traits from se and su types - like tender moist kernels and superior flavor. The augmented supersweet types must be isolated from su and se types of sweet corn.

biocontrol / biological control
Reduction in numbers or elimination of pest organisms by interference with their ecology (interfering with the pests’ life cycle), often by the introduction of parasites or diseases. Part of an integrated pest management (IPM) program.
See IPM

biodegradable mulch
Biodegradable mulch breaks down upon exposure to soil micro-organisms. It is often a combination of polyethylene and paper, or polyethylene and starch. Breakdown is incomplete at the end of a growing season, but the product continues to degrade once incorporated into the soil.
Compare with photodegradable mulch
S ee mulch
See Microclimate Research page

blackspot bruising
Blackspot bruising is caused by a chemical reaction resulting from an impact that damages cells beneath the tuber skin, but does not break the skin, and appears as dark grey-black discolouration of normally white tissue. It takes 24 to 48 hours after an impact for the damaged tissue to change color, and the damaged area can only be seen after the tuber skin is removed.
See Calcium nutrition of potatoes in the Potato fertility page

blossom blight
A fungal pathogen that affects the flowers (occasionally leaves and stems) of many plants. Infected flowers fail to set seed resulting in yield loss. Spores are spread by wind and/or water droplets (rain) from nearby sources (infected crops, crop residues from past infected plants). Causal agent seems to vary from crop to crop and throughout the province.

blossom end rot
Blossom-end rot (picture)is a physiological disorder of tomato, pepper, and eggplant, (and other solonaceous crops) and is attributed to calcium deficiency. This disorder is characterized by dry, brown to tan areas that develop on the blossom end of the fruit. These regions become sunken and may turn black as they mature, and may spread to cover half of fruit.

bolting
Flowering. Often characterized by rapid elongation of the central stem (or main flower stalks) and development of reproductive organs (flowers). In horticultural crops bolting can be stimulated by day length, temperature, or plant stress.

brassica
Any of the various plants in the mustard family (Cruciferae or Brassicaceae). Includes cabbage, cauliflower, brussels sprouts, radish, broccoli, turnip, kohlrabi, and mustard. Also includes many weedy species, and ornamentals such as alyssum and ornamental kale.
Often used synonymously with crucifer

buckskinning
A physiological disorder of potatoes characterized by lighter discolouration of the skin, and a soft, but slightly roughened skin surface similar to suede leather.
See Calcium nutrition of potatoes in the Potato fertility page

cell membrane
A delicate structure which encloses the cell, separating the contents of the cell from the surrounding environment. Also called the plasma membrane. The cell membrane is composed of lipids (fat molecules) and creates a semi-permeable barrier around the cell that allows some substances into (and out of) the cell, while restricting the movement of other materials. In plants, the cell wall is the second most outer layer of the cell, and lays directly beneath the cell wall.
See cell wall below

cell wall
A rigid structure that surrounds, protects and gives shape to plant, fungi and many bacterial cells. Animal cells do not have cell walls. In plants, the cell wall is the outermost layer of a cell, and is made of cellulose.
See cell membrane above

chilling - picture
Damage caused by exposure to cool, but not freezing, temperatures. Chilling causes physiological changes that may affect ripening, storability, and disease susceptibility of horticultural crops. Often a concern during post-harvest handling and storage, but may be an issue for warm-season crops (tomato, peppers, melons) in spring and autumn.
Compare with killing frost

chlorosis / chlorotic - picture
The yellowing or blanching of normally green plant tissue because of a decreased amount of chlorophyll, often as a result of disease or nutrient deficiency.

colorado potato beetle (CPB) - picture of adult, larva
A black-and-yellow striped beetle (Leptinotarsa decemlineata). Reddish-tan to orange larvae feed on the leaves of the host plant. A major pest of potato and other solanaceous crops. Also called potato beetle, potato bug.
See Potato Pest and Disease Management page
See Potato Pest and Disease Management photo gallery

crop cover
A cover (plastic, spun fibers) placed over a large area (several rows) of a crop. In cooler climates, covers are often placed over direct seeded rows or recently transplanted crops to create a warmer, more humid microenvironment to facilitate rapid plant establishment of warm season crops. Can also provide crop protection from insects. Crop covers can also be used as a means to separate varieties to maintain line purity by excluding insects and thus preventing cross pollination.
Also see row cover
Also see low tunnel
Also see Microclimate Research Pages

crucifer - cruciferious vegetables
Any of the various plants in the mustard family (Cruciferae or Brassicaceae). Includes cabbage, cauliflower, brussels sprouts, radish, broccoli, turnip, kohlrabi, and mustard. Also includes many weedy species, and ornamentals such as alyssum and ornamental kale.
Often used synonymously with brassica

cultivar
A race of a plant that has been bred intentionally and maintained through cultivation.
Compare with variety.

day neutral
Day-neutral refers to the light sensitivity of the straberry variety. Day-neutral strawberries are not sensitive to daylength, and will blossom and set fruit no matter how long or short the days are. Day-neutrals will continue to set and ripen fruit all summer long until a hard frost puts them into dormancy.

defoliation
The removal of a plant’s leaves. Intentionally caused by the use of chemicals or mechanical force. May also result from disease or poor nutrition.

desiccant
A chemical (natural or manufactured) that is applied to the foliage to dry down the crop. Often applied to facilitate mechanical harvest of field crops, or to top kill potatoes

determinate
Plant habit characterized by growth in which the main stem ends in an inflorescence (flower stalk) and stops growing. Lateral branches have similarly restricted growth. ie. determinant tomatoes (bush tomatoes).
Compare with indeterminant

double haploid (DH)
A laboratory technique that results in doubling of the existing genetic material - resulting in homozygous, true breeding material in a single generation. This technique has been used to reduce the length of the crop improvement cycle of crops like canola and wheat by several years.
See homogeneous
See homozygous
See Double Haploid Medicinal and Aromatics page

easter egg
An easter egg is a hidden special feature in a movie, computer game/program, or website, usually added by the programmer to reward viewers for paying special attention and noticing "out of the ordinary" elements. This definintion, for example, is an easter egg - one you can get to only by reading through this glossary page. There is another more interesting easter egg in this website, if you look hard enough. Hurry - Gunther is waiting for you!

emergence
The event in seedling or perennial growth when a shoot becomes visible by pushing through the soil surface.
Compare with germination

evapotranspiration
This is the amount of water that transpires through a plants leaves combined with the amount that evaporates from the soil in which it is growing. Used as a guide for how much water a plant needs per day/week/year.
See transpiration

flavonoid
Flavonoids are a group of complex substances which are present in most plants, concentrated in seeds, fruit skin or peel, bark, and flowers. Flavonoids have been shown to be potent antioxidants, and highly sought after in “health foods” for their ability to scavenge free radicals.

flea beetle - flea beetle picture
A small beetle with enlarged rear legs which allow it to jump large distances. Both adults and larvae can be a problem in brassica crops such as turnips, broccoli, and chinese cabbage.
See Root Maggot Management Research Pages for more information.

floricane
A type of raspberry. Floricane raspberries flower and produce fruit on old wood (canes that developed in the previous growing season). Fruiting is earlier in the season than primocane raspberries.
Compare with primocane

gas chromatography
An analysis tool which is used to determine the chemical make-up plant extracts. Chromatography is the process in which a substance is separated into its components and diffused, along with a carrier gas, through a liquid or solid adsorbent for differential adsorption.

genotype
The genetic makeup of an organism or a group of organisms.

germination
The sprouting of a seed. The first visible stage of seed germination is the swelling of the seed as it absorbs water from its surrounding, followed closely by the emergence of the root from the seed coat.
Compare with seedling emergence

germplasm
Raw plant breeding material which is the basis for selection and increasing diversity; could include seeds, genes, tissues or organs. Also, total of the genotypes that constitute a plant species.

growing degree days (GDD)
The number of degrees that the average temperature is above a baseline value. Every degree that the average temperature is above a baseline value becomes a growing degree day. Used by horticulturists and growers to predict the date that a crop will reach maturity.

heat stress
Injury resulting from high temperatures. May be caused during exceptionally hot weather when transpiration rates are limited and the plant cannot cool itself adequately. Can be a problem when crop covers (low tunnels, high tunnels) are used too late into the season, or with inadequate ventilation.
Compare with chilling

high tunnel
High tunnels are unheated, plastic-covered structures large enough to allow crops to grow to maturity, and allow sufficient space for cultivation, spraying, and harvesting to occur with the tunnels intact.
Compare with low tunnel
Also see High Tunnel Research Pages

homogeneous
Genetic description of open pollinated varieties. When all (or most) genes are paired up with their identical genes, so that reproduction (seed set) results in offspring with very similar characteristics. Traditionally achieved through several generations of self-pollinating. In the laboratory homogeneity (homozygosity) can be created in one generation with doubled haploid technology
See genotype
See double haploid
See homozygous

homozygous
Genetic description of open pollinated varieties. When all genes are paired up with their identical genes, so that reproduction (seed set) results in genetically identical offspring. Traditionally achieved through several generations of self-pollinating. In the laboratory homozygosity can be created in one generation with doubled haploid technology
See genotype
See double haploid
See homogeneous

indeterminate
Plant habit characterized by growth in which the main stem continues to elongate indefinitely without being limited by a terminal inflorescence (flower stalk). Vines have indeterminate growth (melons, greenhouse tomatoes).
Compare with determinate

inoculum
The microorganisms or other material used to cause an infection. Also called inoculant.

integrated pest management (IPM)
An ecologically based pest-control strategy that relies on natural mortality factors, such as natural enemies, weather, cultural control methods, and carefully applied doses of pesticides.
See biological control

IRT mulch (infra-red transmitting or wavelength selective)
IRT plastic mulch (Wavelength selective) is used to heat the soil for warm-season crops. IRT mulches contain very specific pigments that allow them to transmit a maximum of near infra-red radiation and a minimum (14-16%) of visible light, thereby reducing weed growth under the mulch. IRT mulches are either green or brown, depending on the manufacturer.
See mulch
See biodegradable mulch
See Microclimate Research page

killing frost
A frost severe enough to damage or kill crops. Different crops have different frost thresholds. ie. Killing frost for melons is 0°C; killing frost for cabbage is -3°C.
Compare with chilling

leaf drop
A common disease of vegetable crops. Commonly caused by the fungi Sclerotinia sclerotiorum and S. minor. Particularly a problem when repeated cropping of an area with sensitive hosts results in high populations of the pathogen in the soil. Minimize risk of infection by rotating crops.
See Vegetable Pest and Disease Management

loam
A soil containing a mixture of clay, silt and sand that is best for the growth of most plants.

low input production
Agricultural production that limits, but does not exclude, the use of synthetic fertilizers and pesticides. Low input production relies on a strong IPM plan and the use of natural products (eg. manure) when possible.
Compare with organic production

low tunnel
Low tunnels are constructed of polyethylene or woven fibre, supported by metal hoops, to create warm, sheltered microclimates preferred by crops like peppers and melons. Low tunnels work by restricting movement of air in the vicinity of the crop, and raising the temperatures for the early establishment of the crop.
See row cover
See Reemay
See crop cover
See microclimate
Compare with high tunnel
Also see Microclimate Research Pages

maggot - root maggot picture
The legless, soft-bodied, wormlike larva of any of various flies of the order Diptera. Root maggots that feed on cruciferous crops feed on the roots, weakening the plants, slowing crop development and leaving the roots open to invasion by rot-causing diseases.
See Root Maggot Management Research Pages
See Pest and Disease Management of Vegetable Crops

microclimate
The climate of a small, specific place within an area as contrasted with the climate of the entire area. Producers can modify the microclimate environment by using plastic mulches, row covers, low tunnels, shelterbelts, etc…
See crop cover
See row cover
See low tunnel
See high tunnel
See mulch
Also see Microclimate Research Pages

mulch
A protective covering placed around plants to heat or cool the root zone, to prevent the evaporation of moisture, limit the growth of weeds, and prevent winter damage in perennial / biennial crops. Can be made of plastic of varying colours, organic materials such as straw, wood chips, shredded bark, leaf matter, or rock chips (commonly used in landscaping).
See IRT mulch
See biodegradable mulch
See photodegradable mulch
Also see Microclimate Research Pages

mycoplasma
A living microorganism lacking a true cell wall. Mycoplasma are intermediate between bacteria and viruses. Some species can cause plant diseases.
See aster yellows

necrosis / necrotic tissue
Dead tissue or cells caused by disease or injury.

nutraceutical
A food or naturally occurring food supplement thought to have a beneficial effect on human health. Nutraceutical vegetables are varieties that have been bred to contain unusually high levels of a substance thought to be healthy.

organic
Food production involving only the use of natural, non processed fertilizers of plant or animal origin, without the employment of growth stimulants, antibiotics, or pesticides.
Compare with Low Input production

organic matter (O.M.)
The part of the soil that includes the decomposing remains of plants and animals, as well as the product of complete decomposition, known as humus.

pathogen
An agent that causes disease, especially a living microorganism such as a bacterium or fungus.

pepper ripening stages
immature – Fruit is not physiologically mature. Will not ripen when picked, will not store well. Seeds are mature.
mature green – Physiologically mature green fruit. Picked fruit will ripen if stored properly. Seeds are likely mature.
mature red/yellow/orange/purple – Fully ripened fruit.

pH
a measure of acidity and alkalinity of a solution, represented by a number from 0-14. 7 represents neutrality. Lower numbers represent increasing acidity, and higher numbers represent increasing alkalinity (more basic).

photodegradable mulch
Photodegradable mulch breaks down upon exposure to UV rays. It is often a combination of polyethylene and paper, or polyethylene and starch. These products may be further broken down by microbial activity once incorporated into the soil.
Compare biodegradable mulch
See mulch
See Microclimate Research page

pollination
The transfer of pollen from an anther to the stigma of a flower.

Post-emergent herbicide
Herbicide applied after emergence of the weed and crop. Usually only effective on exposed plant material, and can be specific to the target pest.
Compare with: pre-emergent herbicide

potato types
processing potato – Potatoes grown specifically for the processing industry. High specific gravities are important. Every process demands very specific tuber characteristics. eg. Potato chips – medium to large sized and round, with a light colour when fried. French Fries – large, brick shaped, and light colour when fried. Common processing varieties are Russet Burbank, Shepody, Snowden.
table potato – Potatoes grown for the table market – unprocessed potatoes sold to the consumer. Medium sized, blemish free, uniform potatoes with attractive colour are demanded by the consumer. Many varieties of potatoes are grown for the table market. Popular commercially grown varieties are Norland (red), Russet Norkotah (russet) and Yukon Gold (yellow flesh and skin).
seed potato – Potatoes grown to be used as seed for the subsequent season. Must be high quality and relatively disease free. Idea seed potato size is approximately 50 g (2 oz).

Pre-emergent herbicide
Herbicide applied prior to the emergence of the weed crop. Usually has soil activity to prevent weed seed germination.
Compare with post-emergent herbicide

primocane
A type of raspberry. Primocane raspberries will flower and produce fruit on new wood (first year canes). Fruiting is later in the season than floricane raspberries.
Compare with floricane

randomized complete block design
A randomized complete block design is the simplest design that uses blocking. Treatments are randomly assigned to experimental units separately within each block in such a way that all treatments occur an equal number of times in each block.
See split plot design

Reemay
A spunbonded polyester material used for low tunnels. Allows 80% light transmission and light frost protection. Manufactured by BAA Fiberweb.
See low tunnel
See crop cover
See Microclimate Research page

Rhizoctonia (black scurf)
Rhizoctonia disease of potato, often referred to as black scurf, is caused by the fungus Rhizoctonia solani . R. solani is a very common soilborne pathogen and is found in most potato-producing areas of the world.
There are two phases of the disease: the stem and stolon phase, and the tuber phase. The first occurs early in the growing season in the form of lesions on the growing tips of sprouts, stems or stolons. The second and most noticeable phase is the formation of sclerotia on tubers. These sclerotia give the name black scurf and look like “dirt that doesn’t wash off." The longer the potatoes remain in the soil after vine kill, the more sclerotia will be formed on the tubers. The fungus overwinters as sclerotia (spores) and mycelium (vegetative growth) on infected tubers, in plant residue, or in infested soils.

row cover
A cover (plastic, polypropylene, or spunbonded fiber) over one or several rows. In cooler climates, covers are often placed over direct seeded rows or recently transplanted crops to create a warmer, more humid microenvironment to facilitate rapid plant establishment of warm season crops. Can also provide crop protection from insects.
See crop cover
See low tunnels
See Reemay
See Microclimate Research pages

runnering
The production of runners. Runners (in a strawberry plant) are above ground stolons (stems) used for vegetative propagation (asexual, or seedless, propagation). Runners will develop roots and leaves, and grow into separate plants if they come in contact with soil.l

senesce
to decline with maturity or age, often hastened by stress from environment or disease.

scab
Scab is a common disease of potatoes characterized by irregularly shaped lesions (often with a rough texture), on the skin of the tuber. There are no above ground symptoms. Scab may not affect crop yields, but greatly reduces potato quality. The bacteria Streptomyces scabies causes common scab (picture), and the fungus Spongospora subterranean causes powdery scab (picture). Powdery scab can result in tuber breakdown in storage.
Also see Potato Disease and Pest Management Pages

Sclerotinia
A common pathogen affecting many vegetable crops. The fungi Sclerotinia sclerotiorum and S. minor cause leaf drop (picture) in lettuce. Sclerotinia is a problem when repeated cropping of an area with sensitive hosts results in high populations of the pathogen in the soil. Minimize risk of infection by rotating crops.
See Vegetable Pest and Disease Management

sequential plantings
Consecutive plantings, or repeated planting/harvesting in one season. Commonly done with short season crops like lettuce, radish, and spinach, where the cropping cycle can be completed several times.
See Sequential Planting pages

shattering
A natural mechanism of seed dispersal, where the seeds are not held within a structure (fruit, capsule) for a long duration. Can be a problem when mechanical harvesting is utilized, particularly if the crop has uneven maturity or seeds mature over a long period of time.

silymarin
The medically valuable compounds sought after in milk thistle. Silymarins have been demonstrated to both protect and alleviate problems with liver and kidney function. Silymarins are present throughout the milk thistle plant, but occur at the highest concentration in mature seed.
See Medicinal and Aromatic Research pages
See Milk Thistle Agronomy page

slip
Relating to melons and the formation of an abscission layer
full slip – Full formation of the abscission layer. When melons are fully ripe, the stem cap (where the vine attaches to the fruit) readily separates from the fruit with a slight tug. Flavour (sweetness) is maximized if melons are allowed to mature fully and harvested at full slip, but storability is limited.
half slip – Partial formation of the abscission layer. Melons appear fully ripe, but the stem cap will only partially separate from the fruit with a slight tug. Flavour (sweetness) is not as high as fully ripened melons, but storability is better.
See abscission layer

solanaceous
Plants that belong to the potato / tomato family (Solanaceae), such as potato, tomato, eggplant, peppers, tobacco, and petunia.

softneck garlic
Softneck garlic (allium sativum var. sativum) is characterized by many small cloves, often forming several layers around the central core. No central scape, or flower stalk, is produced.
See stiffneck garlic
See Garlic Agronomy pages

specific gravity
A measurement of the dry matter in potato tubers, particularly important in the processing industry. Specific gravity is defined as the ratio of the density of any substance to the density of water.
Formula: specific gravity = [(air weight) / (air weight - water weight)]

split plot design
An experimental design that may be used when several treatments are being evaluated at one time. The field may be divided up into main plots to evaluate one treatment, and each of these main plots is further divided into subplots to test the other treatments.
See randomized complete block design

SSPGA (Saskatchewan Seed Potato Growers Association)
The Saskatchewan Seed Potato Growers Association (SSPGA) is a grower owned non-profit corporation developed to provide Saskatchewan seed growers a forum from which they could collectively speak to local, provincial, national and international issues of vital interest to their industry.
Website: http://www.sasktelwebsite.net/sspga/

standard sweet corn (su)
The original sweet corn arose as a mutation of standard field corn. The mutation caused the kernels of the su type of corn to accumulate about twice as much sugar as standard field corn. The su types of sweet corn show good tolerance of cool soil conditions at planting and are often quicker to mature than other types of sweet corn. Conversion of the kernel sugars into starch occurs rapidly after harvest and the post-harvest lifespan of su cultivars is therefore limited. There are relatively few new su cultivars being released as the market has shifted to higher quality se and sh2 types.

stiffneck garlic
Stiffneck garlic (allium sativum var. ophioscorodon) is characterized by robust growth, and the formation of a stiff, central scape (flower stalk) where flowers and small bulbils are formed.
See softneck garlic
See Garlic Agronomy pages

stigma
Part of the female reproductive organ within a flower. The stigma is the upper part of the pistil (the entire female reproductive organ), and the organ that receives the pollen upon pollination.

stomata
Tiny pores on the surface of plant leaves that can open and close to take in and give out water vapor (transpiration), oxygen, and carbon dioxide.

sugar enhanced (se) sweet corn
Sugar enhanced sweet corn kernals have a higher sugar content than standard sweet (su) types and the rate of conversion of these sugars to starch after harvest is slower. These two factors improve the post-harvest quality of the se types relative to the su types. Kernels of se types of sweet corn are more tender, with a higher moisture content than supersweet sh2 types. The se types also have greater tolerance of cool, wet soil conditions at planting than the sh2 types. There is no need to isolate the se types from su corn, but they should be isolated from sh2 types, otherwise the quality of the sh2 types will be compromised.

supersweet (sh2) corn
The shrunken (sh2) mutation results in exceptionally high kernel sugar content (up to 16%) and very slow conversion of these sugars to starch after harvest. Consequently, supersweet types of corn hold their quality for extended periods after harvest, which is a highly desirable characteristic for corn destined for the retail market system. The sh2 types of corn are typically planted later than su and se types as the small sh2 seed is sensitive to cool wet soil conditions. Some consumers find the kernels of sh2 types to be tough. The sh2 types must be isolated from field, su and se types of corn to preserve the desirable sh2 qualities.

synergistic sweet corn
Cobs of synergistic corn cultivars feature a mixture of sh2, se and su kernels - with the ratio of each kernel type varying from cultivar to cultivar. This mixture of se, su and sh2 kernels is designed to capture the individual strengths of each type of corn within a single cultivar. Synergistic types of sweet corn must be isolated from sh2 cultivars, otherwise the quality of the sh2 types will be compromised.

tip burn
A physiological condition of leafy vegetables (lettuce, oriental greens) where the leaf tips die back (picture). Can be caused by over fertilization (too rapid growth), irregular water availability, or nutrient deficiencies, especially calcium.

tomato ripening stages
There are several ways of categorizing tomato ripeness. Listed below are a few of the significant stages of tomato ripening.
Immature – green tomato, very firm and may or may not be full sized. Immature fruit will not ripen after harvesting.
Mature Green – tomato is full size, but still green. Fruit may be slightly softer than immature green. Mature green fruit will ripen if handled correctly during post harvest and storage.
Breaker – a noticeable colour change. Less than 10 % of the surface is not green. Tomatoes at this stage will ripen naturally after harvest if handled correctly.
Turning – between 10 - 30 % of the tomato surface is coloured.
Pink to Light red – between 30 - 60 % of the tomato surface is coloured.
Ripe – more than 90 % of the tomato surface is the mature colour.

top kill
To remove or kill the vegetative part of the potato crop to facilitate good skin set and the formation of abscission layers between the root and maturing tuber. Top killing may be done by desiccation or mechanical defoliation.

transpiration
The process by which water vapor escapes from plants through leaf pores (stomata)
Compare with evapotranspiration

translocation
The movement of soluble material (metabolic products such as sugars) from one part of a plant to another. ie. sugars are translocated from the leaves where they are formed to the developing fruit in a cantaloupe vine.

transplant shock
The environmental change (in moisture, temperature, humidity) that transplants experience following transplanting can cause damage to the roots and shoots of young transplants. Signs of transplant shock include wilting, root death, leaf drop, and even seedling death.

variety
A race or variety of a plant that has been selected intentionally from the wild and maintained through cultivation.
Compare with cultivar.

zip tunnel
A type of low tunnel. Zip tunnels (photo) are constructed of clear non-perforated polyethylene to produce maximum warming, but the tops of the tunnels are always open ... allowing some ventilation. A drawstring system allows the size of this opening to be varied, depending on prevailing conditions and the needs of the crop.
See low tunnel
See Microclimate Research Pages